Using Ground Control Points

Overview

Ground Control Points (GCPs) allow you to achieve survey-grade accuracy across all drone outputs—orthomosaics, elevation models, and volume calculations. By uploading known reference coordinates and tagging them in your drone images before processing, OpenSpace Air can correct positional drift and produce results that are georeferenced to your specifications and consistent across every flight.

GCP sets are managed at the site level and can be reused across multiple captures. You can also configure a coordinate reference system (CRS) for your site at any time—even if you’re not using GCPs.

Before you begin: GCPs must be in WGS84 format (EPSG:4979)—latitude and longitude in decimal degrees, with elevation in meters above the WGS84 ellipsoid. If your GCPs are in another coordinate system (e.g., NAD83, State Plane, NAVD88), you will need to convert them first. Ask your OpenSpace sales representative for CRS conversion instructions. 

Permissions

Step 1: Configure your coordinate reference system

1. Navigate to your site's Drone Settings page.
2. Under Coordinate Reference System, configure your horizontal and vertical CRS.
3. The default is WGS84. If your project uses a different CRS, update this before uploading GCPs.

Note: You can set a CRS for your site at any time, regardless of whether you’re using GCPs.

Step 2: Upload your GCP coordinates

1. On the Drone Settings page, navigate to the Ground Control Points section.
2. Click Download Template and select the template that matches your data format:
   • Latitude/Longitude + Meters
   • Latitude/Longitude + Feet
3. Fill in your GCP data: point name, latitude, longitude, and elevation.
4. Click Upload CSV and select your completed file.
   • OpenSpace Air will automatically match common column name variations (e.g., "lng" for longitude).
   • A minimum of 3 GCP points is required.
   • Your points will be validated and previewed on the map.
5. Review the map preview to confirm your points are in the expected locations.

Step 3: Associate GCPs with a capture

1. When uploading a new drone capture, click Add GCPs in the upload dialog.
2. Your site's existing GCP set will be displayed automatically. Click Apply to associate it with the capture.
3. The capture status will update to Ready once GCPs are applied.

Note: Applying GCPs to a capture will disable automatic ortho calibration for that capture. The two cannot be used simultaneously.

Step 4: Tag GCPs in your drone images

1. Open the capture and select Tag GCPs to launch the tagging workflow.
2. For each GCP point, identify and mark its location in at least 3 drone images.
   • Use the image carousel to find images that contain the GCP marker.
   • Click the exact location of the marker in each image to place a tag.
3. Repeat for all GCP points.
4. Once all points are tagged, click Submit to proceed to processing.

Step 5: Process your capture

1. Click Process to initiate GCP-assisted processing.
2. Processing with GCPs takes longer than a standard capture. Your results will appear in the captures list once complete.
3. If there’s an issue with your GCP data, an error will be surfaced in the processing results.

Managing your GCP set

You can update or replace your site's GCP set at any time from the Drone Settings page.

• Replace CSV—Upload a new file to update your GCP coordinates. Existing captures associated with the previous set will not be automatically reprocessed.
• Delete GCP set—Removing your GCP set will trigger reprocessing of associated captures without GCP data.

Tips

Reuse GCPs across flights with virtual control points (VCPs)
Once you have one high-accuracy GCP-processed capture, you can use virtual control points (VCPs) to align all subsequent quick flights to it—without repeating the full GCP tagging workflow. See Using Virtual Control Points in OpenSpace Air for instructions.

Verifying your results
After processing, use the split view comparison tool to verify alignment between your GCP-processed orthomosaic and your base map.

If you have any questions, please reach out to the OpenSpace Support team at support@openspace.ai.