What are Ground Control Points (GCPs)?
Ground Control Points, or GCPs, are large marked targets on the ground, spaced strategically throughout your area of interest. If you use ground control points with your aerial map, you first need to determine the RTK GPS coordinates at the centre of each ground target.
The ground control points and their coordinates are then used to help drone mapping software accurately position your map to the real world around it. It might be helpful to consider your GCPs as a series of thumbtacks placed on your drone map, as DroneDeploy knows each of these thumbtacks’ exact locations. It can reference their locations when it matches all the other map points.
Read through our guide on using GCPs with Drone Mapping Software.
Why would you use GCPs?
GCPs effectively increase the absolute or global accuracy of a map. They help ensure that the latitude and longitude of any point on your map correspond accurately with actual GPS coordinates. This is important when precision mapping and true global accuracy are needed.
Learn more about mapping accuracy and improving accuracy here.
Learn more on EPSG codes, reference systems, projections or sea levels here.
How to successfully capture Ground Control Points (GCPs) for drone mapping.
Check out our 6-minute overview video for a summary:
Collection of GCPs:
- Initially, read through our GCP Request checklist to help you get started.
- You'll require at least 4 GCPs and need to spread these as widely and evenly throughout your site as you can.
- If there are objects on your site that you are specifically interested in, like a stockpile or structure foundation, make sure to place markers near those points of interest.
- If there are large terrain elevation areas, try to place markers near the highest and lowest areas of the site.
- When placing GCPs around the perimeter, DroneDeploy recommends a 50ft (15m) buffer zone between the edge of the map and the GCPs location. This will ensure there is enough image coverage to carry out the processing.
- Adding Checkpoints helps you validate your GCP maps' relative and absolute accuracy. Learn how to process them with DroneDeploy: GCP Checkpoint.
- Make sure you know the EPSG code used for your measurements: ask your surveyor what EPSG code they are using, or set your device to WGS84 / Code 4326.
Check out Best Practices Ground Control Points (GCPs).
GCP flights are flown just like any other flight. The only difference is you are now capturing GCP targets in your imagery that will later be used to increase the accuracy of your map. Make sure your camera is in focus and set up correctly. If the GCP targets are not in focus, the process will not result in the same levels of accuracy. It is always a good idea to ensure good weather over the area you will be flying to that day. High winds, low clouds, or precipitation can make flying and mapping difficult.
For more information, please see this article: Making Successful Maps.
Uploading and processing your images:
To ensure your GCPs process accurately and efficiently, DroneDeploy must receive specific information for your project. If you are new to DroneDeploy and, or GCPs, it can be challenging at first but easy right after that. Please check out the below articles for some guidance:
- An article that shares the whole process of uploading and processing GCPs: Processing GCPs with DroneDeploy.
- Upload your GCPs all at once as a new project: Creating a new project with GCPs.
- When uploading your GCPs, you may need to correct the formatting to successfully upload in the browser tagging tool: GCP. CSV File Formatting.
- If you are using AeroPoints - download the CSV of your collected data points; this file will be compatible with DroneDeploy's CSV uploader.
- Needing help with the Coordinate Reference System (CRS): Defining a CRS for new and existing projects.
- If you can't find your EPSG code in DroneDeploy, search our supported EPSG codes: EPSG Service.
GCP processing is available for Advanced, Teams and Enterprise customers and individual customers ($49 per map). If you are currently on a Lite or Individual plan and are interested in adding GCPs, please get in touch with firstname.lastname@example.org. We can help determine if GCPs are the best option for your mapping project.
If you have any issues at all, reach out to email@example.com.