Ground Control Points are used to increase the geospatial accuracy of a 3D map or model.
Ground Control Points
Ground Control Points (GCP) are points on the ground with precisely known latitude and longitude coordinates. Many users measure the area they intend to survey ahead of time and place markers on the scene before they fly. Then, they document the coordinates of each GCP marker and enter the data in a file to upload along with their images.
Ground Control Point files can be uploaded in the following file types: TXT, CSV, XLS, XLXS, or OBS.
When you upload a Ground Control Point file, Mapware will attempt to place the points in your images. You can review the automatic placement in each image and adjust the location of your ground control points if needed.
Are Ground Control Points Required?
Ground control points are optional. You can easily process a model in Mapware without any GCPs.
While 3D models can be created without ground control points, GCPs provide increased accuracy in dense point clouds, orthomosaic maps, and digital elevation models. They are useful when extreme geospatial accuracy is essential to a project.
How Do I Adjust Ground Control Points?
After uploading data that includes Ground Control Point files, you will have the chance to review the data you uploaded.
To review and change the placement of a Ground Control Point, click on "Review GCP". In the Ground Control Point review screen, each image with a ground control point will be shown in thumbnail view. To review your ground control points, click "Review GCP" below each image.
The image will open, and the location of your ground control point will be indicated by a red point.
Click and drag on the red point to move it to the correct location. When you drop the point, you will be prompted to confirm the location. Click "Confirm placement" to confirm the change.
To return to see all of your images with GCPs, click the back arrow next to the image file name.
How Do I Add a New Ground Control Point?
You can also add a new ground control point that is not included in your uploaded data.
Add New GCPs from the GCP Review Screen
On the Ground Control Points (GCP) review screen, click the plus sign next to your listed GCPs.
The New Ground Control Point screen allows you to select the coordinate reference system you want to use. (The list includes all coordinate systems in the EPSG Geodetic Parameter Dataset, a public registry of spatial reference systems.)
Give your new GCP a name, set the longitude, latitude, and altitude of the GCP, and click "Create".
Mapware will determine which photos in your data set contain the new GCP and place it in those photos. You will be able to review this GCP along with all other GCPs in your data.