Drone maps are a powerful way to understand what’s happening on the ground — whether you’re measuring stockpiles, checking site progress, or monitoring environmental change. But for those maps to be useful, they need to be more than just sharp images. They need to accurately reflect real-world positions. That’s where Ground Control Points (GCPs) come in. GCPs are one of the most reliable ways to improve the positional accuracy of drone outputs.
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Ground Control Points are specific locations on the ground that have been accurately surveyed and marked. These known reference points are used during drone data processing to help align outputs like orthomosaics or digital elevation models (DEMs) with real-world coordinates.
GCPs are usually flat markers — like checkerboard tiles, crosses, or painted targets — placed on the ground before a drone flight. They’re designed to be clearly visible from above.
Here’s how the process typically works:
Depending on the project, GCPs might be placed by a surveyor, engineer, or a trained drone operator. After the flight, temporary markers are usually removed — although permanent GCPs are sometimes used for long-term monitoring or recurring surveys.
In drone mapping, there are two main types of accuracy to be aware of:
It’s possible to have high relative accuracy without GCPs. Many drones — even with standard GNSS — can produce internally consistent outputs. That means distances, shapes, and volumes within the map can still be useful for certain tasks.
But without GCPs (or RTK/PPK corrections), those same outputs might not be correctly georeferenced — meaning they could be a few meters off from their actual position. If you're overlaying drone data with other spatial layers, tracking change over time, or submitting outputs for compliance, that global alignment matters.
Most drones are equipped with standard GNSS receivers — GNSS stands for Global Navigation Satellite System, and includes satellite positioning systems like GPS (US), GLONASS (Russia), Galileo (EU), and BeiDou (China). These systems tell the drone where it is when each image is captured.
However, standard GNSS can have positional errors ranging from 1 to 5 meters due to things like satellite geometry, atmospheric interference, or terrain. For high-precision work, that’s a wide margin of error.
By contrast, using GCPs allows you to correct and align your outputs with known ground positions — improving accuracy and ensuring your results are georeferenced correctly to your chosen system. (Not sure how coordinate systems work? Here’s a simple guide to coordinate reference systems)
Some drones come with RTK (Real-Time Kinematic) or PPK (Post-Processed Kinematic) capabilities. These systems use correction data from a known base station to improve accuracy — and in many cases, they reduce the need for GCPs. (Learn more about PPK, GPS and RTK geotagging in drone aerial imagery).
That said, many professionals still use at least a few GCPs alongside RTK/PPK to validate results and ensure quality — especially for regulatory or compliance-grade projects.
On Birdi’s Ultimate Plan, you can upload GCP files during processing, visualize their placement on your map, and use them to improve the positional accuracy of your outputs. This is especially useful for work in mining, construction, environmental monitoring, and carbon project verification.
Ground control points aren’t always required — but when accuracy is critical, they can make all the difference. By anchoring drone data to verified ground locations, GCPs help ensure your maps and models aren’t just visually accurate, but geographically reliable too.
If you’re working on projects where precision matters, get in touch to learn how GCPs fit into your workflow with Birdi.