Elevation Grid Creation in Global Mapper: Creating a DTM

Written by: Mackenzie Mills,  Application Specialist

The Elevation Grid Creation tool in Global Mapper uses loaded 3D data, data with x, y, and z values, to create a raster gridded elevation layer. This layer can then be exported in one of the supported elevation formats, or used for further analysis or to create a map.

A generated elevation grid layer displayed in the 3D viewer. 

The first method Global Mapper offers to generate elevation grid layers is the Triangulated Irregular Network or TIN method. This method connects 3D point features or the vertices of 3D line and area features into a network of triangles. From there, the program interpolates over the triangular faces using the feature elevation and slope values to generate an elevation grid layer.

Triangulation Method Process: Source Contour Line Data, Contour Lines with Vertices connected by the Triangulation Network, Triangulation Network with Interpolated Raster Grid, Output Gridded Elevation Layer.

With the Lidar Module, Global Mapper not only provides point cloud classification and processing tools, but the program also provides additional methods for generating an elevation grid. These additional options are all variations on the binning method. This method is better suited for point cloud processing because not every single point in the point cloud is used to generate the output grid.

Typically point clouds are quite dense and you don’t need to use every single value to generate an accurate output. In fact, using every point often results in an elevation grid layer that contains lots of noise and appears rougher than the actual study area. The binning methods help to reduce this noise by spatially binning the data into areas corresponding with the size of the output grid cells. One value from each of the spatial bins is then used to generate the gridded layer. The elevation value from each bin that is used to generate the grid is determined by the specific binning method that is selected. For example, the Binning Minimum Value method uses the minimum elevation value from each bin to generate the grid. The Lidar Module currently offers three variations on the binning method, with two additional variations coming soon.

  • Binning (Minimum Value – DTM)
  • Binning (Average Value)
  • Binning (Maximum Value – DSM)
  • Coming Soon – Binning (Median Value)
  • Coming Soon – Binning (Variance)
Elevation Grid Creation dialog from left to right: Using only 3D Line or Area Features, Triangulation Method Selected using a Point Cloud, A Binning Method Selected using a Point Cloud.

A digital terrain model, commonly referred to as a DTM, is an elevation model that describes the terrain or ground of an area as opposed to the structures and features on top of the ground, such as buildings and vegetation. Conversely, a digital surface model, or DSM, aims to show the structures and features on top of the ground.

When creating a DTM, you will likely want to use the binning minimum value method. Since lidar is not ground-penetrating, the minimum values detected in the point cloud are most likely to be true ground measurements.

Another option you have in your workflow is to further identify ground points by classifying your point cloud using the classification tools available in the Lidar Module. The automatic classification tools allow you to perform rough classifications that you can then clean up and fine-tune with manual classification.

When generating the elevation grid layer, there is the option to further filter the points of your point cloud to use only points within a specific class, with specific flags, or in a designated elevation range. This filtering will help to further narrow down the points available to consider when Global Mapper is building the elevation grid layer.

The Filter Lidar Points dialog accessed from the Elevation Grid Creation Options.

Water bodies such as ponds, lakes, and rivers may not provide consistent point cloud data. When generating an elevation grid that contains water-covered areas, you may want to flatten those areas to a specified elevation value. This can be done by including a 3D area feature in the data used to create the grid, and using the grid creation option to ‘Use 3D Area/Line Features as Breaklines’. This will burn the area feature into the output grid at the elevation designated by the area feature, thus flattening the noise within the area. This can be used for road features, building footprints, or any other area features as well.

A path profile showing the point cloud and generated terrain grid that used a breakline to flatten the water area, and the same grid in the 3D viewer showing the flattened water area and rockier shore. 

To compare a few different elevation grid creation methods, the path profile tool can be used. Below is a path profile over three elevation grids all using different methods. You can see that the binning method grid appears smooth compared to the triangulation method grid.

A Path Profile Comparing Generated Elevation Grids

With an elevation grid layer created to show the elevation as a surface, you can continue your analysis in Global Mapper to generate contour lines, generate watershed areas, perform volume calculations, or any other analysis function. To see more of what Global Mapper can do for you, please visit the Tips & Tricks page or request a demo or a trial today.

GeoTalks Express – Session 2 Questions & Answers

The second of Blue Marble’s GeoTalks Express online webinar series, entitled Why do you need the Lidar Module?, was conducted on April 15th, 2020. During the live session, numerous questions were submitted to the presenters. The following is a list of these questions and the answers provided by Blue Marble’s technical support team.

 

Would it be possible to get an xyz file into the Lidar Module?

When you load your XYZ file, the Text File Loader will open automatically. It has an option to load as a lidar point cloud. 

 

Will the pixels to point tool work with standard aerial photography from fixed-wing aircraft?  

​The Pixels to Points tool in Global Mapper uses the structure from motion process to construct the point cloud, orthoimage, and mesh outputs. This process relies on overlap between adjacent images showing identifiable features from slightly different angles as the camera moves over the area. We do recommend at least 60% overlap between images, but it is always best to try for more. 

This issue with most standard aerial photography is that there is likely little to no overlap between the produced image frames. Without this overlap, features cannot be identified in multiple images and triangulated to then generate the output layers. That being said, if your images are geotagged and have the required overlap, you may be able to use them in the Pixels to Points tool. 

 

How long does it roughly take to run a pixels to points extraction for a couple of hundred images? Thanks 

How long does it take to generate a project of this size for the ortho, point cloud and mosaic using the pixels to point tool?

 It would be hard for me to give an exact time estimate on P2P processing. There are quite a few variables involved​, such as your settings within the tool, details of the imagery you’re using, hardware specs, etc. I would say generally this process is a more computationally intensive one than some other basic processing in Global Mapper, so it could range from as little as a few minutes, to longer, again all depending on the above criteria.

 

​So, you don’t need Pix4D or Agisoft PhotoScan (Metashape)?

Yes, the Pixels to Points tool can construct point cloud, orthoimage, and mesh outputs like Pix4D and Agisoft do. After generating these outputs with the Pixels to Points tool from the Lidar Module you can continue working right in Global Mapper to classify, grid, analyze your point cloud further.

 

​What are the recommended PC specifications for using the LiDAR module?

Minimum and recommended system requirements for Global Mapper and the Pixels to Points tool can be found here in the Global Mapper knowledge base.

 

​Can you speak *conceptually* to the difference between LiDAR data and point cloud data collected via an automated drone flight? 

​It sounds like you have some experience working with both types of data. The main differences stem from how the data is collected and the point cloud is generated. As you noted, lidar data collection is active and has multiple returns. This allows data to be collected from below tree canopy as some of the returns will likely pass beneath ​it and be able to return ground reflected points. True lidar data also collects true intensity and other characteristics that cannot be generated from drone collected images. 

A point cloud generated from drone collected images can only construct what the images show. For example in areas with dense vegetation or no clear view of the ground, the program cannot accurately identify ground since the images do not show it. This then can impact your classification of the point cloud using automated classification tools. 

​With drone collected images generating your point cloud there are RGB values assigned to the points, and with the Pixels to Points tool you can easily construct an orthoimage along with the point cloud. In Global Mapper if you have a point cloud without RGB values and an image for the area, you can apply color to the point cloud. ​

 

Do you have automatic powerline extraction tools? or is it done manually? Are breaklines automatically generated or are they manually collected?

Global Mapper does have automated Powerline Classification and Extraction tools.

When it comes to breaklines, this would depend on how you want to work with them. You could load in breaklines if you have them in an existing file already, you can incorporate them when making a terrain layer as well. Making Contours  may help you find them too.

 

Can you get measurements in feet and inches?

In Configuration > General > Measure Units you can ​change the distance units displayed when using the Measure tool in Global Mapper. 

 

Is there a limit in size or number of pictures to process in Pixels to Point from pictures taken using drones?

We do not impose a limit on the number of pictures ​you can use in the Pixels to Points tool, but the amount of data you can process is limited by your machine memory. This is also impacted by the quality setting in the pixels to points tool and whether or not you are reducing your images. 

When you go to run the Pixels to Points process Global Mapper does a memory estimate and if it is predicted you will run out of memory, the program will suggest you reduce your image sizes by a certain factor. 

 

Do you have a document describing best practices for collecting Drone footage to generate a point cloud? Is there a link to tutorials for Drone footage capture?

We don’t have any video tutorials on collecting drone images for processing with the Pixels to Points tool, but you can find our data collection recommendations here in the Global Mapper knowledge base

 

​Will there be a technical webinar for the Lidar Module too?

More information on upcoming GeoTalks Express webinars can be found here. We also have many past webinars posted on our YouTube channel including a series on lidar processing in Global Mapper. ​

 

​Can you talk more about free lidar sources please?  

There is freely available lidar data out there. In Global Mapper we include some of these sources in the Online Sources dialog. There is a LIDAR folder you can expand and the sources listed here will link you to an organization’s download page where you can then download data for your area of interest. ​

 

​Is this software actually processing the raw images and x,y,z coordinates from the UAS flight? Or are you processing the point cloud in another software and transferring it into your software for combination with other file extensions?

The Pixels to Points tool in Global Mapper is taking the collected drone images and running through a process in the program to construct a 3D point cloud, orthoimage, and 3D mesh output. These layers are created in Global Mapper with the use of the Lidar Module. ​In the demonstration shown in this GeoTalks Express session, no other software programs were used to process the drone images into the three output layers. 

 

​Can we use a GPS enabled DSLR handheld camera for image collection vs. a drone?

You can use a GPS enabled DSLR camera to collect images to then process in the Pixels to Points tool. Ideally, you will want to keep the data collection as uniform as possible using a fixed focus and no zoom. You can mount a DSLR camera to a drone, or collect images without a drone as long as the images meet the data recommendations. This includes clear images that have the required overlap and are geotagged. 

 

Does the LIDAR module support SLG and SL2 files such as are produced by Lowrance side scan sonar units on boats?  

Global Mapper supports SLG and SL2 formats for import and export, and you do not actually need the Lidar Module addition to load the file types. A full list of file formats supported in Global Mapper can be found here.

 

Is it possible to detect the position of overhead line conductors with the pixel to points process? 

​Global Mapper with the Lidar Module contains some automatic classification tools including a powerline classification tool. ​This tool allows you to take a point cloud, like one generated by the Pixels to Points tool, and detect and classify points that represent powerlines. Once these points have been classified, you can use the feature extraction tool to extract the powerlines to vector features. 

 

​Does LiDAR module have the ability to tie in ground control points for aerial imagery?​

​In Global Mapper you can rectify images using control points with the Image Rectifier tool. ​This tool can be used when loading images that contain no georeference information, or you can adjust a loaded image by right-clicking on the layer in the control center and selecting to Rectify

​When generating an image from the Pixels to Points tool, the ground control points you place in the Pixels to Points dialog will be used when generating the output layers. ​

 

​What point cloud file formats does LiDAR module support? Can I use an export from AutoDesk RECAP and import into the LiDAR module?

AutoDesk RECAP files are supported in Global Mapper and the Lidar Module. A full list of file formats supported by Global Mapper can be found here

 

I have a network license, but would like to use the software in the field while flying in order to check that I have good data before leaving the site. Is there a way to use my network license as a single floater license?  

You can borrow a network license seat from the server for use offline. This will allow you to use the Global Mapper and Lidar Module licenses off-network. 

 

Do you have to have the lidar point cloud loaded with the images to create a 3D mesh in the Pixels to Points tool?  

The mesh created from the Pixels to Points tool is created from the point cloud also generated by the tool. You do not need to have any previously created point cloud layers loaded to generate a mesh through the Pixels to Points tool. 

 

​Is the 3D mesh give you a similar file as colorizing the point cloud?​

The mesh generated from the Pixels to Points tool is textured with the drone collected images. You can create a mesh from a selected section of a point cloud with the Lidar Module but it will be textured with the RGB or elevation shader colors of the points as opposed to the drone collected images. 

 

How could the Lidar Module be used for mineral exploration?  

​The Lidar Module allows you to process and ​work with point clouds. What specific kind of analysis are you looking to do?

You can classify and generate elevation grids to model your study area. If you are able to collect your own data using a lidar scanner or processing drone collected images you can generate models of the area for specific dates and compare as they change over time using the Compare Point Clouds tool or the Combine/Compare Terrain layers option. 

 

Is it possible to do automatic extraction line. ie kerb of road or boundary from a shape (home, etc.).?​

In Global Mapper with the Lidar Module, you can do some custom feature extraction to place control points along a feature in a point cloud and extract a vector line. This is not automated extraction for all like features in a point cloud, you would need to extract each individually. 

 

​It is possible search for the best fit line from all points (wire line), for example : powerline wire?​

You can extract vector features for powerlines from a point cloud using the Feature Extraction tool. Before using the tool you must classify the point cloud to identify the points representing the powerline features. Global Mapper supports a few automatic classification tools including one to classify powerlines

 

Can your Pixels to Points program utilize precise camera coordinates instead of ground control points?  

If you do not have accurate ground control points or do not wish to use any, you do not need to enter them in the Pixels to Points tool. Without ground control points the camera coordinates, and other EXIF information, will be used alone to position the images for processing. 

 

Can your Pixels to Points program accommodate both precise camera coords as well as gcp coords in an integrated optimization (adjustment) of the camera positions and tie points? 

Currently in Global Mapper, the camera coordinates are adjusted during the process and the entered ground control points are used for this adjustment.

 

​Do you provide for inputs to control the weighting of coordinates – whether of ground control points or of camera exposure positions?​

The Pixels to Points tool does not allow for the weighting of control points or weighting between the set of camera coordinates and ground control points. We do have an open development ticket (#GM-9093) on adding the ability to weight control points. 

 

​The mesh file – is it a triangulation model or a square GIS mesh?

The mesh file generated from the Pixels to Points tool is a triangulation mesh. The mesh is a vector feature made up of triangular faces and textured from the drone collected images. 

​​

​Is it possible to import commonly-used camera parameters (ie Phantom 4 V2) to help with processing? If not are there plans to add this capability or can you discuss how to set up with currently available option for best results.​

Global Mapper keeps a database of camera models and parameters. Common camera models are recognized from the input image metadata, but if the camera is not part of this built-in database, you will be prompted to select the model and enter the sensor width. This entered information will then be stored by Global Mapper in the user data folder in a sensor_width_camera_database.txt file. 

The Phantom 4 V2 is in the built-in camera database and should be recognized from the input image metadata. 

 

How do comparisons with ESRI ArcMapper and ArcPro with the LP360 Extensions?

With the addition of the Lidar Module in Global Mapper, you can classify point clouds, with automatic classification tools or by manual classification, extract features, and compare and analyze point clouds in many ways. Additionally, in the Lidar Module you can use the Pixels to Points tool to construct a point cloud from drone collected images. From using the Lidar Module tools you can easily continue analysis with any of the Global Mapper tools

The Lidar Module is built into the Global Mapper general GIS solution. It is not a standalone application that would require you to use limited extension tools in another application or transfer files between programs during your workflow. This allows for a more seamless workflow since all of the needed tools are in one program. 

What processes do you most often perform in your point cloud analysis? Are there any processes you are specifically interested in?

 

​Is there a way to adjust roll, pitch and yaw or is the point cloud matching only based on xyz?  

The camera position and parameters like roll, pitch, and yaw are found in the metadata for each image used in the Pixels to Points tool. This information is used to position the images when processing them. You can load metadata for images from a text file in the Pixels to Points dialog. This method would allow you to alter the information as needed before applying it to the images. 

 

What are the benefits of using the Lidar Module as opposed to using Terrasolid?​

G​lobal Mapper with the Lidar Module offers classification, feature extraction, filtering, 3D viewing, point cloud construction from collected images, along with many other tools. Some of these functions are similar to those in Terrasolid, but Global Mapper supports a wide variety of file formats and our development team is always pushing to improve the existing tools and create new ones for point cloud processing. 

Since the Lidar Module is part of the Global Mapper program you can seamlessly go from working with the Lidar Module tools to using any of the Global Mapper tools in your analysis.

What processes do you most often perform in your point cloud analysis? Are there any processes you are specifically interested in?

 

Drone Flight Tips When Using Global Mapper’s Pixels to Points Tool

Written by: Mackenzie Mills,  Application Specialist

As drones gain popularity and more people begin collecting their own data for analysis, tools like Pixels to Points in Global Mapper become more important in workflows. The Pixels to Points tool is the structure from motion (SfM) process to create three-dimensional data and image outputs from sets of drone-collected images. In many situations, this is a great and cost-effective alternative to collecting lidar (light detection and ranging) data.

The SfM process used in the Pixels to Points tool identifies features in multiple images by matching pixel patterns in the images. Features identified in multiple images are then triangulated and constructed in 3D space to generate three-dimensional outputs, including a point cloud.

Whether you are experienced with drone data collection or are new to this method, it is worth learning or reviewing some tips for quality data collection. The most important requirements for drone-collected images that you intend to process with Pixels to Points (structure from motion) are overlap and clarity.

The overlap between collected images is very important as it allows the tool to identify features in multiple images in order to triangulate them in space and construct the output layers for the area. With sets of images that contain little to no overlap, the Pixels to Points tool cannot identify features from multiple views in order to triangulate and construct the outputs. This will result in an error, or outputs that contain missing data. We recommend a minimum of 60% overlap between adjacent images, but you should always plan for more.

Drone images of a baseball field.
Drone images of a baseball field being aligned.

The images you intend to use need to have clear and identifiable features so that the Pixels to Points tool can identify them based on clear pixel patterns. This means two things, (1) the images need to be in focus, and (2) the images need to have identifiable features. Images that are blurry due to the camera shaking or vibrating, or out of focus will yield incomplete or no results from the structure from motion process. This is because the noise(or movement that makes the images blurred) inhibits the program’s ability to identify features. Areas with no identifiable features will similarly result in errors. Common scenes that encounter this issue are areas of snow cover, all white with no features, or bodies of water with no lasting features that can be identified.

Comparison of a focused and a blurred image due to noise.
Comparison of a focused and a blurred image due to noise.

Depending on the goals of your project, you may want to use different methods for collecting images. Some basic variables that go into how you plan your drone flight are pattern, height, and angle.

Drone flight patterns.
Drone flight patterns.

For two-dimensional mapping to generate an elevation model of a ground area and not surface features, capturing nadir images (looking straight down) from as high up as possible is best. For this data collection, you can use a simple mow the lawn pattern moving back and forth over the area of interest.

For 3D modeling of high relief terrain, buildings, and structures, you’ll want to capture oblique images in order to capture the sides of features. Here you would fly at a lower height, 150 to 200 feet, with a front-facing camera and collect data in a checkerboard pattern, going back and forth over the study area, then back and forth again crossing over the previous flight lines. This will help to capture the sides of terrain features from various angles for a better three-dimensional reconstruction.

For structural modeling of a specific building or stockpile feature, you’ll want to capture oblique images as you fly at a lower height in a circle around the object of interest. This will capture images covering the sides of the feature to create a detailed model.

Types of angles of drone images.
Types of angles of drone images.

Flight planning is an important part of data collection when working with drone collected data. Understanding the variables and data requirements for the Pixels to Points tool and other SfM processes will help you to collect images better suited for processing. In turn, this will create higher quality results for further work.

GeoTalks Express – Session 1 Questions & Answers

The first in Blue Marble’s GeoTalks Express online webinar series, entitled Getting to Know Global Mapper, was conducted on April 1st 2020. During the live session, there were a number of questions submitted to the presenters. The following is a list of these questions and the answers provided by Blue Marble’s technical support team.

 

What is the spatial extent of the data being loaded? 

I believe that you were asking this question in reference to loading data from an online source. When loading online data you have a few options to choose the extent to load. The extent is specified in the connect to online data dialog and you can load data for only the current screen bounds, within a certain distance of an address or coordinate, within a selected area feature, or for the entire source bounds. In the session today I demonstrated loading only data for the current screen bounds. 

When loading data from an online source keep in mind that this data is streamed and relies on your network connection to load the data. Smaller areas of data will likely load faster.

 

How do you define the bin sizes in the depth example?

When setting up the point styles for the lake depth points I manually entered and set the style for each value using the New Value button on the Point Styles tab. 

You can use the Load Values option to automatically load values from a layer of features. You can load each unique value, or if the values are numeric Global Mapper will recognize this and give you the option to load only key values (minimum, average, average + two standard deviations, maximum) and then blend the colors between these values. 

 

How do you get contour lines? 

In Global Mapper contour lines are created from a loaded elevation grid layer using the generate contours tool. In this tool there are many options for generating contour lines including the option to set a specific contour interval in meters or feet. 

 

Is it possible to know the date from World Image Data?

Blue Marble does not create or update any of the data streamed from the online sources. For more information on any built-in online source, image or otherwise, you can right-click on the source name from the Online Sources dialog and select to Display Source Web Page/Terms of Service

 

Can Global Mapper produce contours from point data?

Contour lines need to be created from an elevation grid layer. You can generate an elevation grid from 3D point data, and from there generate contour lines

 

Can the fly through be saved as a file? 

Yes, you can save a fly through as a video. From the 3D viewer click on the save the fly through button on the toolbar and you will have options to select the quality, resolution, frame rate, and format for the video recording of the fly through. 

 

If you delete something is there an undo button?

You can use the keyboard shortcut ctrl + z to undo deleting features right after you have deleted them. This undo function only covers the last feature(s) you deleted and will not work if you delete a feature and then perform another action in Global Mapper. 

 

Is the profile view 1:1 or is it vertically exaggerated? 

The path profile view is exaggerated to fill the path profile window. There are values noted on both the x and y axes of the profile view. You can specify a specific elevation range or scale for this tool in the Path Profile Settings

 

Can you talk about how to find free lidar data online?

There is freely available lidar data out there. In Global Mapper we include some of these sources in the Online Sources dialog. There is a LIDAR folder you can expand and the sources listed here will link you to an organization’s download page where you can then download data for your area of interest. 

 

Do the menu tiles – icons highlight only when applicable choice? The pencil selects as edit – the feature chosen triggers other option choices?

Specific to the digitizer toolbars, you may have noticed that some tool icons appear grayed out and are unable to be selected. This is true for many feature editing tools until you select a feature with the digitizer. Once you have a feature selected you should see these options brighten and be selectable based on the feature(s) you have selected. 

 

What do the tree and building toolbar buttons do?

These buttons are part of the Lidar Classification toolbars that are used to work with point cloud data in the Lidar Module. We will be talking about the Lidar Module in the next GeoTalks Express session on April 15th. 

We do have previously recorded webinars and videos that specifically focus on and talk about the Lidar Module if you are interested in learning more about this module now. You can find these videos here on our YouTube channel

 

How are the lat and long extents set up in the map layout editor?

When you create a map layout you select with the bounds or the scale and center point of the data that should be displayed in the map layout. To add coordinate grid elements to the map, click to select the map frame then right-click and select Properties. Here you can edit the map view element and on the Grid Fram tab add coordinate grid information to the map view. 

 

Can we georeference a scanned map in Global Mapper? 

Yes, you can georeference scanned maps and other layers in Global Mapper. To georeference a layer you would use the Rectification tool. For this tool you should start by loading some reference data into Global Mapper, then from the File menu select Rectify (geo reference) Imagery to load your scanned map image and open the Image Rectifier dialog. 

 

Is there any way to create contours with intervals less than 1m or 1ft?

Yes, you can specify a contour interval in the contour generation tool dialog. The only unit options are meters and feet, but you can use decimal values to specify a smaller contour interval. 

 

Can you export a path profile as a point or CSV file?

You can export a path profile to multiple formats from the File menu in the path profile dialog. From this menu you have options to export the profile as a CSV or XYZ file. 

 

Can Global Mapper incorporate multiple surface models so the profile view shows more than one profile? 

Yes, if you have multiple overlapping terrain layers loaded in Global Mapper you can create a path profile view that will show separate lines for all terrain layers. To enable this option you will need to go to the Path Profile Settings and check the option to Draw Separate Line for Path from Each Terrain Layer. In addition you can enable the option to Draw Legend when Drawing Separate Layer Lines

 

When importing USG 3DEP elevation data – is there a way to know its accuracy and time/date of collection?

Blue Marble does not create or update any of the data streamed from the online sources. For more information on any built-in online source, image or otherwise, you can right-click on the source name from the Online Sources dialog and select to Display Source Web Page/Terms of Service

 

Can you create a contour map from the lake points or a thematic map? Like a heat map?

From the lake depth points used as an example, you could generate an elevation grid to show depth, and generate contour lines from that gridded elevation layer. 

You can create a thematic map by changing the point style for the lake depth points in the layer options. 

Global Mapper also has a density or heat map tool that you can use to show clusters of points or attribute values. 

 

How can you extract an area to AutoCAD Civil 3D? Image? Terrain?

Global Mapper supports many file formats for both import and export. For vector features these do include common AutoCad formats DWG and DXF. For raster image and elevation formats Global Mapper has many options including JP2000 (image), GeoTIFF (image or elevation), and DEM (elevation). Are there specific formats you are looking to work with?

 

Can you do image registration in Global Mapper?

You can georeference images and other layers in Global Mapper. To georeference a layer you would use the Rectification tool. For this tool you should start by loading some reference data into Global Mapper, then from the File menu select Rectify (geo reference) Imagery to load your scanned map image and open the Image Rectifier dialog. If you are looking to adjust the rectification for a layer, right-click on the layer in the control center and select Rectify

 

Can you make final presentation plots with title box and other presentation features?

Yes, you can create maps with titles, legends, and other elements using the Map Layout Editor. From here you can export the pages to PDF files or images for use in presentations. 

 

Can you use this to show areas of a certain percent slope, like slopes greater than 20%?

In Global Mapper you can use a custom shader to show specific slope values or slopes over a certain threshold in a different color. When creating a custom shader the slope values should be specified as degrees. 

You also have the option to create vector features from slope values by using the Create Areas from Equal Values tool. You can then search these vector features to identify and work further with a specific slope value or range of values. 

 

Can the 3D-views generated by the fly-through tool all be exported in a batch?

If you have multiple fly-through paths defined in Global Mapper, when you go to save the fly-through you will be prompted to select a path in the Fly-Through Options dialog. You can select All Paths which will play and record all the fly throughs back to back recording them to one video file.

 

Are there any size limits on vector files?

Although there are no size limits on files when working in Global Mapper, you should make sure that your computer is powerful enough to handle the size of data you are working with and the processes you are running. We do have some system requirements and recommendations for running Global Mapper, but an issue some users run into is insufficient memory when performing analysis functions with large datasets. 

 

Is it possible to change the units in the path profile?

Yes, you can change the distance units in Global Mapper and the elevation units used in the Path Profile tool. To change the distance units (x axis units in the path profile) go to Configuration > General > Measure/Units and change the Distance Units. To change the elevation units in the path profile (y axis units) open the Path Profile Settings and change the Elevation Display Units.

 

What projection does the feature retain? Can we specify the coordinate system when exporting?

When exporting features or layers Global Mapper will use the workspace projection to write out the files. The workspace projection is also what is used to draw and display the data in Global Mapper. This projection can be viewed, set, and changed in Configuration > Projection

 

Can you round this calculation to a desired precision?

If you are asking about precision related to calculating new attributes, you can use a function to specify a number of decimal places for a numeric value. 

  • FIXED(expression1 [, expression2]) : Formats expression1 as a numeric value, to an optional number of decimal places, specified by expression2, if present; if it’s not present, then the default is 2 decimal places.

 

Do you have more style options for the scale bar?

In the Map Layout Editor you can edit the scale bar feature to customize aspects like font, spacing, and color. All added elements are able to be edited like this in the Map Layout Editor. 

 

If you crop and image, can you export only the cropped area and if so, what resolution will it keep? 

When you crop an image the image still displays with the original resolution. When exporting an image Global Mapper will export the image that is shown, so if an area is cropped out that area will not be exported. In the export options you do have the option to specify the resolution for the exported image. 

 

I’m a secondary science teacher (grades 7-12) that teaches earth science. Do you think the global mapper can be applied to teaching topographic mapping? It seems a bit too difficult for students (who are around 14-15 years old) to use, but maybe there’s something that I could do with it as a demonstration tool.

In Global Mapper you can most certainly work with and create topographic maps. Take a look at the generate contours tool to show and have students understand how contour lines fit a gridded elevation surface. With the 3D viewer and path profile tool you could show how the 3D data/information is translated to a flat or 2D map. 

If you are unfamiliar with Global Mapper I encourage you to request a trial license and start by looking at the Getting Started Guide, and maybe some of our self training lessons

 

How do we change the openspace label zoom during exporting raster images?

When viewing online data, like the World Street Maps or Open Street Maps data, that has labeled areas and features, these labels are part of the raster image. This means that the scale of the features and labels is linked to the zoom level of the online source.

You can control some of the detail shown for online layers on the Display tab of the layer options. In this dialog you should see a slider for Online Layer Detail Offset that can be used to adjust the amount of detail shown based on using a higher or lower zoom level for the online data. 

 

How can I generate a database of points over the image?

If you are looking to generate a regular grid of point features over a loaded image layer, you can use the Create Regular Grid of Features tool from the digitizer (advanced) toolbar. This tool will generate a grid of features (points, lines, or areas) and you can select under Grid Placement/Orientation to fill rectangle. Using the Select Rectangle button you can then set the bounds to the bounds of a specific image layer.

 

Can I draw a line joining the deepest or shallowest depth points of a dataset?

With the digitizer tools in Global Mapper you can select specific points and then choose to create lines features from selected points. To select points to connect into lines, you can search the vector data for features based on an attribute value and select them, or select features more directly with the digitizer tool. 

Additionally, you can generate a gridded elevation layer for the depth points and then perform further analysis. Some analysis functions Global Mapper supports are the generation of contour lines and watershed and stream creation over an area of known elevation. 

I see that you were interested in creating or working with a bathymetric surface with water shading

If you do not have a bathymetric surface, but instead have point features like in the Lake Depth example shown during the GeoTalks Express session, you can generate a gridded layer from this 3D vector data. You can then shade this layer with any of the built in shaders, or create a custom shader to show the colors/values you would like. 

You also have an option to display a water level at a specific elevation which would allow you to show a water line along a coastal area or bank. 

Geo-Challenge — March 2020 Answers

How Well Did You Do?

Name the Island? – Réunion

 

Name the Country? – Poland

 

Name the Monolith? – Rock of Gibraltar

 

Name the River? – Niger River

 

Name the Capital Cities? – La Paz and Sucre

Got a Drone? Now What? — Using Global Mapper with Your UAV

Let’s start with a question. How many of you currently own a Segway? Unless you moonlight as a mall cop or run an urban tour company, you probably decided not to jump on that gyroscopically-controlled bandwagon. If the hype that surrounded the release of this ‘revolutionary technology’ was to be believed, we would long since have abandoned our cars, redesigned our cities, and be living much more fulfilling lives. Alas, the reality has fallen a little short.

The emergence and proliferation of Unmanned Aerial Vehicles (UAVs) or Drones, on the other hand, while not accompanied by a cacophony of hyped-up fanfare, promises to have a much more profound impact on our lives. If current speculation is to be believed, within a few short years, the skies overhead will be swarming with delivery drones, traffic monitoring drones, and even people-moving drones.

For those of us in the mapping industry, this eye-in-the-sky technology effectively addresses one of the perennial challenges that we face: where do we get data, and more specifically, where do we get current data? Traditionally, we have depended on often inadequate and outdated public geospatial data archives or expensive commercial sources. With the advent of readily accessible UAV technology, on-demand data is within anyone’s reach.

The rapid growth of UAV ownership has resulted in an interesting dilemma for some would-be pilots. Having purchased the hardware and collected some data, many are often unclear as to what exactly they can do with it? Over the last couple of years, I have attended several UAV-focused tradeshows and a question that I am often asked is, ‘What can I do with Global Mapper?’ The answer: many things.

Initial Flight Planning

Among the freely available online data services in Global Mapper are high-resolution aerial imagery, Digital Elevation Models (DEMs), aviation charts, and topographic maps.

Before hitting the launch button, it is a good idea to virtually reconnoiter the project area. What possible obstructions are in the vicinity, what are the terrain characteristics, are there any nearby buildings or other facilities that might have overflight restrictions, what is the coverage area? These questions and more can be answered by loading the relevant data into Global Mapper and conducting some rudimentary pre-flight analysis. Among the freely available online data services are high-resolution aerial imagery, Digital Elevation Models (DEMs), aviation charts, and topographic maps. Global Mapper’s drawing tools can be used to delineate the extent of the project site to determine coverage area and to draft an initial flight plan to optimize the data capture process. All of this data can be transferred to an iOS or Android device running Global Mapper Mobile to allow field checking of the flight plan parameters.

Geotagged Image Viewing

Images can be loaded into Global Mapper as picture points creating a geographic photo album. Derived from the coordinate values embedded in the image files, the location at which each photo was taken is represented by a camera icon in the map view.

One of the most basic functions of a UAV is taking photographs and as we will discuss below, with sufficient overlap, these images can be processed into a 3D representation of the local area. Before proceeding with this more advanced functionality, the images themselves can be loaded into Global Mapper as picture points creating a geographic photo album. Derived from the coordinate values embedded in the image files, the location at which each photo was taken is represented by a camera icon in the map view. Using Global Mapper’s Feature Info tool, each photo is displayed using the computer’s default image viewer. Viewed in the 3D Viewer, the camera icons will appear above the terrain or ground providing a precise representation of the drone’s altitude when each image was captured.

3D Reconstruction

The functionality of the Pixels to Points tool transforms simple drone-collected image files into a dataset that can be used for countless 3D analysis procedures.

Incorporated into the optional LiDAR Module, beginning with the version 19 release of Global Mapper, the Pixels to Points tool is used to analyze an array of overlapping images to create a 3D representation of the environment. This powerful component identifies recurring patterns of pixels within multiple photographs and employs the basic principles of photogrammetry to determine the three-dimensional structure of the corresponding surfaces. While the underlying technology is extremely complex, as is typical in Global Mapper, the user’s experience is very straightforward. Simply load the images, apply the necessary settings for the camera system, add ground control points if available, click the Run button, and wait while it creates a high-density point cloud and, if required, a 3D model or mesh. The functionality of the Pixels to Points tool transforms simple drone-collected image files into a dataset that can be used for countless 3D analysis procedures.

Orthoimage Creation

A byproduct of the aforementioned point cloud generation process is the option to create an orthoimage. Defined as a raster layer in which each pixel’s coordinates are geographically correct, the orthoimage is generated by gridding the RGB values in the point cloud. Given its inherent accuracy, this 2D imagery layer can be used for precise measurements or as a base layer for digitizing or drawing operations.

DTM creation and Terrain Analysis

Global Mapper can generate a Digital Terrain Model (DTM) from point cloud data.

As mentioned previously, the Pixels to Points-generated point cloud represents the raw material for numerous analysis procedures in Global Mapper. As with any unprocessed dataset, some QA, cleanup, and processing will be required before embarking on any meaningful workflow. Fortunately, the software offers a plethora of editing and filtering options, including noise point removal, spatial cropping, ground point identification, and automatic reclassification. After isolating the points representing bare earth, the gridding tool is employed to create a Digital Terrain Model (DTM), a 3D raster layer that depicts the ground surface. In turn, this terrain layer can be used to create custom contour lines, to calculate volume, to delineate a watershed, to conduct line-of-site analysis, and, if overlaid on a previously created DTM, to identify and measure change over time.

Video Playback

Aside from capturing still images, most UAVs are equipped with the necessary hardware to record video. Beyond simple recreational use, this functionality is useful for building or asset inspection, strategic reconnaissance, forestry inspection, and in countless other situations where a remote perspective is needed. Global Mapper includes an embedded video player that will play this recording while displaying the corresponding position of the UAV in the map window. The determination of position is derived from the per-vertex time stamp recorded in the track file recorded during the flight. After loading this file as a line feature, and associating it with the corresponding video file, the playback is initiated from the Digitizer’s right-click menu.

LiDAR Processing

The Global Mapper LiDAR Module offers a set of tools for identifying, reclassifying, and extracting these features as vector objects.

Not too long ago, it was generally accepted that, due of the size and weight of the required equipment, LiDAR collection could only be carried out using a manned aircraft. This simple fact contributed to the high cost and logistical challenges of the LiDAR collection process. Today, miniaturization of the LiDAR apparatus has reached the point where it is within the payload capacity of many larger drones. Given the limited range of the aircraft, drone-collected LiDAR is only viable for small, localized projects however it does allow frequent re-flying of a project site and is thus ideally suited for change detection. Global Mapper, along with the accompanying LiDAR Module, offers a wide range of tools for processing LiDAR data. As previously mentioned, points can be filtered and edited before creating a surface model for terrain analysis. Compared to photogrammetrically created point cloud data, LiDAR provides a more complete three-dimensional representation of non-ground features such as buildings, powerlines, and trees. The LiDAR Module offers a set of tools for identifying, reclassifying, and extracting these features as vector objects.

Fundamentally, UAVs and maps have much in common. Both are intended to provide a remote, detached perspective of an area of interest and allow us to see spatial distribution and patterns in our data that would not otherwise be detectable. It is understandable, therefore, that one of the primary functions of a drone is to provide data that can be used for creating maps and other spatial datasets. Global Mapper is ideally suited for this type of workflow and it provides an extensive list of tools that can be used by drone operators.


A thirty-year veteran in the field of GIS and mapping, and a lifelong geographer, David McKittrick is currently Outreach and Training Manager at Blue Marble Geographics. A graduate of the University of Ulster in Northern Ireland, McKittrick’s experience encompasses many aspects of the geospatial industry, including cartographic production, data management, marketing and sales, as well as software training and implementation services. McKittrick has designed and delivered hundreds of GIS training classes, seminars, and presentations and has authored dozens of articles and papers for numerous business and trade publications.

 

How to Compare Point Clouds Using Global Mapper v21.1

Written by: Mackenzie Mills,  Application Specialist

In many areas of GIS,  change detection can be a powerful analysis tool. Comparing datasets through time can add another dimension to your work as you can visualize and measure how a study area changes. This type of analysis is becoming particularly important as drone mapping and collection of first-hand data are more common. Change detection analysis can also be very useful when looking for natural change in an area, like the impact of a natural disaster or new vegetation growth year to year; or a man-made change, like the progress of construction in an area or deforestation; or change made to the data by previous edits.

In the release of Global Mapper version 21.1, the Compare Clouds tool was introduced to detect change points between overlapping lidar or point cloud layers. Previously in Global Mapper, change detection was only available using the Combine/Compare Terrain Grid tool, which creates a new elevation layer based on the difference in the per-pixel Z-values of the overlapping layers using the subtraction setting.  The output of the new Compare Clouds tool is a layer containing the points that have changed between the input point clouds. 

To use the Compare Cloud tool, start by loading the point clouds you would like to compare into Global Mapper. Select the Compare Could tool from the Lidar Tools toolbar. 

Compare Lidar Point Clouds
Compare Lidar Point Clouds

In the Point Cloud(s) to Compare Against box, select the starting or original point cloud. This is typically the first or earlier pass over an area. The cloud(s) selected in the Point Cloud(s) to Find Changes In box will be compared to the “Point Cloud(s) to Compare Against when the tool is run.

This new tool works to compare point clouds by having the user input a distance to use for comparison. This Minimum Distance Between Point Clouds value allows for a looser or tighter comparison of the clouds. This setting is important when comparing point clouds because they are made up of individual points and not interpolated like a terrain grid. It is unlikely that the point clouds you are looking to compare will contain points in the exact locations, so a threshold (specified in point spacings, meters, or feet) is required for comparison. Any points from the Find Changes In point cloud that do not have a corresponding point in the Compare Against cloud will be considered changes in the area.

When the process runs, those points in the second layer that have been found to have shifted beyond the designated threshold when compared to the original layer will be marked as having changed. After running this process, you will find a new layer added to the workspace containing only the points that have changed.

Points detected to be changed using the Compare Cloud tool in Global Mapper
Points detected to be changed using the Compare Cloud tool in Global Mapper

In the image above, you see an area of rocks where some have been removed between point cloud one and point cloud two, after running the Compare Cloud tool we see the selected (red) areas are the points detected to be changed.

After identifying change in an area using the Compare Clouds tool, you may wish to classify the points detected as changed or delete them to reconcile multiple datasets. Alternatively, you may want to generate gridded layers to show the changed areas and layer these changed grids over the original or use the Compare Against layer.

This powerful new tool speeds up the process of change detection on 3D data by directly comparing two point clouds to find points with significant change. This change detection functionality can be applied in a wide variety of industries including agriculture, forestry, and engineering. Take a look at the latest release of Global Mapper and the Lidar Module to bring this streamlined workflow into your own data analysis.

How to use Global Mapper’s Raster Reclassify tool

Written by Jeff Hatzel, Senior Application Specialist

With the release of Global Mapper v21.1 comes the addition of an exciting new tool, Raster Reclassify. The development of this tool, like so many in Global Mapper®, was heavily driven by requests from our users. The initial release of this tool allows users to modify the pixel values of a palette image. A common use case for this might be to adjust the classes with a landcover file to create a new layer with a simplified set of classes. Let’s look at a more advanced workflow: using Raster Reclassify to adjust the values of an image created from classified lidar.

Hint: If you’d like to learn about this tool in detail, review the Raster Reclassify Knowledge Base page!

Using Lidar Classification Codes to Make a Raster Layer:

If you’re familiar with the Create Elevation Grid tool in Global Mapper, you know that this tool allows you to create a terrain layer based on the elevations within the source point cloud. You may also know that when working with lidar data, this tool allows you to create a grid-based on a variety of lidar attributes and properties, for example, classifications.

Classified lidar data
Classified lidar data (left) was gridded based on its classification code to make an output raster (right).

This resulting file represents multiple lidar classes from the source point cloud. The classes follow the same color scheme used to display lidar by classification. However, it’s possible we may only have an interest in a specific set of classes or an individual class, buildings for example. We’ll address that with Raster Reclassify.

Hint: Take a look at the different Grid Type options in the Create Elevation Grid tool.

Raster Reclassify to Highlight Classes of Interest:

The Raster Reclassify tool (part of the Analysis Menu) allows you to adjust the values of the source layer. In this situation, we want to focus on buildings. We’re going to merge all non-building classes: ground, low, medium, and high vegetation, bridges, powerlines, and water. Buildings will be retained as a unique class.

Raster Reclassify
Raster Reclassify allows you to load the source palette from a reference file. You can choose which classes you want to reclassify, adjusting their description, color, etc.

This tool creates a new output layer within the current Global Mapper workspace. As you can see below, that layer will now only show the newly created classes you outline in the Raster Classification Rules section of the Raster Reclassify tool.

Source file comparison
The source file (left) compared to the reclassified layer (right). The reclassified layer now only shows two classes, based on the rules set in the Raster Reclassify tool.

Hint: Want to display different layers side-by-side in the same workspace as we’ve done in some of the above images? Check out Multiple 2D Map Views!

What’s Next?

Products created by Raster Reclassify can be used in a variety of applications. Some may be final deliverables for reclassified landcover datasets, used to make or adjust clutter grid files, or any other number of possibilities.

How will you use the Raster Reclassify tool?

Keep an eye out in the future for new functionality in this tool, including the ability to reclassify terrain data and non-palette imagery!