What are Ground Control Points (GCPs) & Checkpoints?

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What are Ground Control Points (GCPs)? 

Ground Control Points (GCPs) are precisely surveyed reference points strategically deployed within your area of interest using ground targets to enhance the geospatial (absolute) accuracy of aerial maps. GCPs provide ground truth coordinates, acting as anchor points for DroneDeploy’s photogrammetry process.


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Think of your drone map as a sprawling digital canvas. To ensure it accurately reflects the real world, you need anchors—enter GCPs. Imagine each GCP as a survey marker that records its exact coordinates. DroneDeploy collects these recorded coordinates that you upload and uses them to meticulously align your map pixels with real-world coordinates. The more anchors, the tighter the fit, resulting in higher accuracy.



What are Checkpoints? 

In practicality, GCPs and Checkpoints are physically the same. Also the surveying and recording process is identical up until the point where they are processed. Checkpoints play a crucial role in verifying the accuracy of your drone maps within your Ground Control Point (GCP) workflow.

Think of GCPs as anchors tethering your map to the real world, and checkpoints as beacons illuminating any remaining discrepancies. By using both, you gain a comprehensive understanding of your drone map's accuracy and ensure it faithfully reflects the reality you're measuring.





Why would you use GCPs? 

Standard drone GPS is like a compass – good for general direction, but not pinpoint precision. GCPs are used when the precise alignment of your map to real-world coordinates matters. This is crucial for:

  • Surveying: Every inch/centimeter of alignment matters for land development, construction, and infrastructure projects.
  • Volume Calculations Over Time: Comparing precise volumes of stockpiles, excavations, or reservoirs to previous captures or design files translates to accurate financial calculations.
  • 3D Modeling: Accurate GCPs underpin detailed 3D models for simulations, engineering analysis, and more.

Remember: GCPs are your precision anchors. Deploy them strategically and watch your drone maps transform from drone images to reality-aligned maps.


Why would you use Checkpoints? 

Here's why they're so valuable:

  • Independent Verification: While GCPs provide ground truth coordinates for processing software, their placement itself can be susceptible to minor errors. Checkpoints act as independent validation points, located throughout your map, but outside the set of GCPs used for processing.
  • Measuring Real-World Accuracy: Measurements you receive for GCPs reflect how well your GCPs were surveyed and tagged relative to their real world coordinates. Checkpoints, however, reveal how well your map reflects the actual real-world features on the ground. This real-world accuracy is crucial for practical applications like construction measurements, volume calculations, or asset tracking.
  • Identifying Spatial Drift: Over long distances, drone maps can suffer from geospatial drift, where small errors accumulate and distort the overall accuracy. Checkpoints help detect and quantify this drift by comparing their measured coordinates with their expected locations on the map.
  • Confidence and Trust: Accurate checkpoints bolster the confidence and trust you can place in your drone maps. By verifying real-world accuracy, you can be sure your data is reliable for decision-making, analysis, and sharing with stakeholders.
  • Targeted Improvements: If checkpoints reveal discrepancies, you can identify the areas or specific factors impacting accuracy. This allows you to refine your GCP placement, adjust processing parameters, or investigate potential sources of error for future flights.



Learn how to capture GCPs and Checkpoints here 


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