November 14, 2023

Top 5 Pixels to Points Features to Improve Your Photogrammetric Processing Workflow

Written by: Amanda Lind


Pixels to Points is a photogrammetric processing tool within Global Mapper Pro that uses overlapping drone/UAV images to create photo-textured 3D models, orthoimages, and high-resolution point clouds. These generated data models can then be used in Global Mapper to measure terrain volume, asses structures, create detailed base maps, and more. Here are the top five features to improve your processing:

The Pixels to Points Wizard Simplifies Data Input and Settings Decisions

p2P wizard open to the choose output options in Global Mapper
Choose from multiple output options to determine settings in Pixels to Points.

Pixels to Points Wizard is designed to increase ease of use for existing users and make photogrammetric processing more approachable to new users by streamlining settings choices. Simply follow the directions to import your drone/UAV images and choose your most important output, including the option to run a quick result for quality assessment. Global Mapper adjusts the Pixel to Points settings to match your input, providing an optional follow-up option to tweak the settings if desired. You can also choose to create DSM, control lines, and other options automatically. Use the primary dialog to add control points and assess more advanced settings such as masking and color harmonization. 

Ground Control Points Improve Positioning During Processing

Ground Control Points (GCPs) are point features collected in the field using a high-accuracy device that can be used to improve the overall accuracy of the generated data. The location information from the GCPs is used as a basis for aligning the scene, taking precedence over the less accurate UAV camera positions. The GCPs must be manually tagged to their individual pixel locations in each image where they appear. To improve this process, the Pixels to Points tool offers the ability to see images that contain the same ground control points. When a ground control point is selected, the tool automatically suggests and highlights all image file names that may contain that point. This functionality makes the process of placing ground control points faster and more intuitive. 

It is also possible to use Ground Control Points after the output files have been generated. Global Mapper provides various tools for this, including 3D rectification and the Lidar QC tool, which can also provide accuracy assessment information.

Ground Control point as seen from above
Ground control points can be anything that is visible from the imagery, such as this placed target.

Image Masking to Exclude Unwanted Areas from Images

Not all parts of an image are ideal or necessary in photogrammetrically generated point clouds. The New Mask button in the Pixels to Points tool allows users to cut out unwanted areas from images and exclude them from processing. These areas are typically swaths of data that tend to not reconstruct well in a point cloud, like sky or water. Masking also allows users to crop their data down to focus on specific interest areas, shortening the point cloud generation process.

masking imagery in Global Mapper
Users can either automatically mask images by selecting by color, or by manually drawing a selection in the Pixels to Points tool.

Post Processing Report

Separate from the log file, which is highly detailed by nature, the ‘Post Processing Report’ is designed to summarize pertinent information from the data generation process efficiently. The new Post Processing Report is polished, easy to read, and includes essential information a user of your data products will want to see. It consists of a project summary chart reporting resolution and coverage area, nadir perspective photos of the generated output data, and more. For more information, see this blog: Post Processing Report.

Post Processing Report image in Global Mapper from Pixels to Points
The Post Process Report is useful for sending to customers, or using as a reference for settings used.

Visualizing Image Coverage 

Photogrammetrically generated point clouds can require hundreds of drone-captured images. 3D data is generated based on the overlapping perspectives of these images. Ground coverage polygons can be used to show the approximate ground coverage of drone-captured photos. To make it easier to manage and visualize the ground-coverage area of each photo, Global Mapper Pro’s Pixels to Points tool provides multiple methods for displaying the ground extent of each input photo. 

The easiest way is to click on an image in the workspace using the Feature Info tool. The polygon will display, and the image will open. To generate the report and more permanent polygons, load the images into the Pixels to Points (P2P) tool, select the image(s) you would like to measure the overlap of, then right-click and choose “Load Ground Coverage Polygons for Selected images.” The coverage polygons will be generated in the workspace, and the Overlap Report will open in your default browser. For more information, see this blog: Determining Overlap Percentage in Drone Collected Imagery

Coverage polygons in Global Mapper
Displaying coverage-area polygons can help users visualize the overlap of adjacent selected images.

If you would like to work with UAV collected images and lidar data in Global Mapper Pro, download a 14-day free trial today! If you have any questions, don’t hesitate to get in touch.

If you enjoyed this blog, you may also find these other resources useful:

Got a drone? Now what? Mapping with your UAV

Ask the Experts: Analysis of drone data using Global Mapper Pro’s Pixels to Points tool

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