When producing 3D models via photogrammetry, checkpoints can be helpful in verifying the models absolute accuracy. The difference between Checkpoints and Ground Control Points is listed below: 

- Ground Control Points (GCPs) are points with known coordinates measured using RTK/PPK GNSS receivers or total stations. GCPs are used to accurately georeference a project during the  processing an and reconstruction.

- Checkpoints are used to assess the absolute accuracy of the model once processed, and are not used for georeferencing the project.

To upload checkpoints within Strayos, click on the options next to the project which you are looking to upload the points to: 

Next, upload your CSV file of measured checkpoints: 

Apply the appropriate headers to the CSV within Strayos and select the correct CRS: 

Once uploaded, a map view will then appear. Here, you will see a green bullseye show the measured position from the CSV file. Move the blue marker to where the checkpoint exists on the model. This will then compare the difference between the measured position and the as processed position. 

To view results, click on the download option from the upper right hand corner and select the PDF for "Checkpoints Report" 

The report will display the actual values measured by your GPS, uploaded from the CSV file, in comparison to the position on the processed model. The Mean, Sigma and Root mean Square Errors will appear below.