As an inherently versatile and interoperable GIS application, Global Mapper has become an essential component of the geospatial toolkit for companies, government departments, and organizations of every imaginable size and type. While the software’s popularity in certain market segments can be directly attributed to a preemptive marketing strategy by Blue Marble, the same cannot be said of the Unmanned Aerial Vehicle (UAV) industry. Instead, the reason why many UAV operators found and embraced Global Mapper can be attributed to word-of-mouth recommendation from others in the field.
With the rapidly expanding use of UAVs for commercial data collection, a bourgeoning market has emerged for data processing software tailored to the needs of the needs of the UAV community. Consequently, many commercial and open-source software developers have jumped on the bandwagon and have begun the process of creating tools to address this demand. Global Mapper, on the other hand, has been around for almost two decades and has proven to be ideally suited to the requirements of the UAV industry. For many UAV operators, the quest to find an affordable, easy-to-use, yet powerful data processing application has ultimately led them to this remarkable application.
So what role does Global Mapper play in commercial UAV operations?
Global Mapper’s expansive streaming data service provides access to a wealth of invaluable map layers that form the foundation for the mission planning process. High-resolution aerial imagery and terrain layers can be accessed on-demand providing an initial three-dimensional visual context for a project area. Locally available vector files can also be overlaid to address concerns such as property ownership, regulatory issues, potential obstructions, and optimal takeoff and landing sites. Intuitive digitizing and drawing tools can be employed to delineate and measure the extent of the project area and supplementary attributes added to record the flight details in their spatial context. Finally, a high-quality project proposal map can be generated in georeferenced PDF or hardcopy format for sharing with a client or customer.
For most UAV operators, the true value of Global Mapper comes to the fore after the mission has been flown. Transforming raw data into a viable commodity or finished product is Global Mapper’s forte, and image processing is a major part of that workflow. The software offers a powerful image rectification tool for applying geographic intelligence to captured images by anchoring them to known coordinates or manually placed control points. Multiple images can be mosaicked or stitched together to form one contiguous file and the overlapping images can be feathered to smooth the transition from one image to the next. Image manipulation options are also available including contrast, saturation, and transparency adjustment. For advanced users, a raster calculation function can be used to analyze the characteristics of multiband images using a predefined or custom formula, the most common of which is NDVI analysis for vegetation assessment using the red and near infrared bands.
Point Cloud Processing
Increasingly, UAV operators are generating 3D point cloud files during the data collection process. Traditionally this data, often generically referred to as LiDAR, has been collected using piloted aircraft at relatively high altitude resulting in lower density point coverage. As the raw material for terrain analysis or feature extraction, the quality of the final product is intrinsically linked to this point density, so UAV-derived point cloud files are typically superior to those derived from conventional LiDAR collection. Global Mapper, along with the optional LiDAR Module, offers an array of LiDAR processing tools for editing, cropping, and filtering the data. Noise points can be systematically flagged and removed and a vertical quality control process can be implemented to adjust the elevation values to surveyed control points.
For most LiDAR or point cloud users, terrain analysis is the ultimate objective, a process that requires the non-ground points to be initially identified and filtered from the data. Using the remaining ground points, a simple gridding process transforms the XYZ values into a raster Digital Elevation Model: a three-dimensional representation of bare earth. Many of Global Mapper’s advanced analysis functions are derived from this gridded data, including watershed delineation, line of sight analysis, and view shed modeling. For UAV-collected data, one of the most powerful and commonly used terrain-based functions is volume calculation. Global Mapper offers a variety of tools for this purpose from simple pile volume calculation, derived from delineating the bounds of the pile or depression, to the more complex cut-and-fill optimization process, in which the terrain is flattened to an elevation that equalizes the volume of material to be cut and filled.
The advent of UAV-collected, high-resolution point cloud data has led to a myriad of applications for the technology: from vegetation monitoring to archeology. To address the growing need to detect recognizable patterns within the data, several automatic reclassification tools have recently been integrated into the Global Mapper LiDAR Module. Points representing buildings, vegetation, and utility cables can be identified and reassigned to the appropriate LiDAR class. These reclassified points can then be used to extract or create 3D vector features (points, lines, or polygons) of the objects they represent. A manual extraction option is also available whereby custom lines or areas can be created using a series of cross-sectional views through a point cloud. Feature extraction can also be applied to imagery allowing patterns of pixel colors to be used as the basis for creating polygons.
Data exporting and sharing
No spatial data processing workflow is complete without addressing the essential requirement for sharing the outcome or results and, once again, Global Mapper is well-equipped for this task. Any collected or created data layers, regardless of format, can be easily reprojected and converted to meet the needs of the client. Cartographic layout tools are available for designing printed maps or for generating geospatial PDFs representing the project site. Global Mapper can even create a 3D PDF allowing anyone with a PDF reader to render a three-dimensional model of any 3D data. For UAV applications, one of the most interesting project visualization options in Global Mapper is the creation of a 3D flythrough. Created from the flight path of the UAV and, if applicable, integrating a video recorded during the mission, the display will render the video while following the flight progress on the 2D map. Even without the availability of an accompanying video, the 3D flythrough can be simulated using any loaded terrain or point cloud data and the 3D line feature that is used as the basis for the fly-through visualization can even be exported as a GPX file for use in the UAV’s navigation system.
Global Mapper has become an essential application for many research organizations and pioneering companies in the professional UAV field. As Global Mapper continues its evolutionary development, these users will play a pivotal role in shaping the software’s functional makeup to ensure it is meeting the needs of the UAV community at large. If you are not currently using Global Mapper, why not download a free trial copy.
David McKittrick is a Senior Application Specialist at Blue Marble Geographics in Hallowell, Maine. A graduate of the University of Ulster in Northern Ireland, McKittrick has spent over 25 years in the field of GIS and mapping, focusing on the application and implementation spatial technology. McKittrick has designed and delivered hundreds of GIS training classes, seminars, and presentations and has authored dozens of articles and papers for a variety industry and trade publications.