IN THIS ARTICLE
For the AutoGCPs detection algorithm to be successful, the following requirements have to be met.
- Image quality has to be good (blurry images, low contrast make the algorithm fail).
- Images have to be geolocated (5-10 m accuracy is enough) in WGS84.
- Images have to be taken nadir. Oblique images are not supported.
- Only squared and diagonal targets are supported (Black and white targets are supported, other colours may work in some circumstances).
- GCPs must be placed at a distance of at least 10 m from each other.
- GCPs must have a projected coordinate system which is included at https://epsg.io.
- Follow the instructions to create a new dataset.
- Once at step 3. GCPs automation, select Upload file.
- Browse the CSV file which contains the GCPs details and click Open.
- The GCPs are imported.
Define the following properties for the GCPs.
- Coordinate system: Drag and drop or browse the .prj file with the coordinate system definition (preferred) or use the search functionality by clicking I don't have a PRJ file. More information about coordinate system files in How to select the GCP coordinate system when working in the Cloud.
- Diagonal target size: Specify the diagonal length of the targets in centimeters or inches.
Once the GCP file has been imported, click See and edit control points to access the control points Table. The user can check the coordinates, change the type of the control points and swap Easting with Northing coordinates.
By clicking Map, an OpenLayers map is displayed with the GCPs and Checkpoints. It is a good way to check that the coordinate system has been well defined. If there is no coordinate system defined, the GCPs and CPs can not be displayed on the control points Map.
By clicking on the points, they can be changed from GCP to CHECKPOINTS or the other way around.
Click Save to save the changes.
Click Replace file if the results are not satisfactory. Click to delete the CSV file.
Click Process to conclude the dataset creation and to start uploading the input files for processing.
- The dataset starts to be processed.
- The AutoGCPs detection algorithm will run. In case the GCPs are not found, an email is sent to the user email address explaining that no GCPs were found and the processing will be done without using them.
- An email is sent when the process is finished with the Quality Report of the project attached.
An AutoGCPs report (PDF) is also generated and available for download. This report shows the detected marks for each point and it is intended to be used to ensure the GCPs have been correctly marked automatically. More information on how to download this report in How to download results from the Cloud.
An example of report for AutoGCPs marking follows.