What are Checkpoints?
Checkpoints are Ground Control Points (GCPs) used to validate the relative and absolute accuracy of your GCP maps. The Checkpoints are not used for processing. Instead, they are used to calculate the error of the map by comparing the known measured locations of the Checkpoints to the coordinates of the Checkpoints shown on the map.
Why are Checkpoints relevant?
In the construction and surveying industries, it is important to empirically validate the relative and absolute accuracy of the map data. By adding Checkpoints and following the ASPRS standards for Checkpoint accuracy, it allows licensed surveyors to specify that a map processed using photogrammetry is survey-grade.
How do I add Checkpoints to my GCP map?
1. To add Checkpoints to your GCP process, simply make sure that the name of the GCP Label in the .CSV file contains the word Checkpoint. Please visit our GCP .CSV File Formatting to correctly format your CSV file.
2. You can also turn a GCP into a Checkpoint when reviewing the GCP images during the tagging process. You can click on the blue GCP button above the EDIT square. This will turn the GCP into a CHX (Checkpoint).
Before
After
How many Checkpoints can I add?
You can add as many Checkpoints as you want, just ensure that you are still using at least 4 quality non-Checkpoints GCPs to process your map.
Example of the Accuracy Report for GCPs and Checkpoints.