When should I use GCPs vs RTK/PPK?

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Choosing between GCPs and RTK/PPK in drone mapping can be tricky, but ultimately, you might benefit from using both for optimal accuracy and project efficiency. Here's a breakdown of why:

 

GCPs

Advantages

  • Sub-inch/Centimeter-level accuracy: Ideal for projects demanding high precision (land surveying, construction, volume calculations).
  • Cost-effective for smaller areas: Fewer GCPs needed when also using RTK/PPK.
  • Provides ground truth data: Verifies the accuracy of drone-derived coordinates.

Disadvantages

  • Time-consuming: Setting up and surveying GCPs takes additional time and effort.
  • Not ideal for large areas: Large-scale deployment can be impractical and expensive. Changing site conditions can make the long-term placement of GCPs incredibly difficult.
  • Prone to errors: Improper surveying, poor GCP markers, and poor tagging can affect overall accuracy.

 

 

RTK/PPK

Advantages

  • Real-time or post-processed corrections: Improves accuracy significantly in real-time or during post-processing compared to standard GPS maps.
  • Faster data acquisition: No need for setting up or surveying physical points.
  • Suitable for large areas: Efficient for covering vast landscapes without GCPs.

Disadvantages

  • Lower accuracy than GCPs: Typically a lower level of accuracy in the z-axis.
  • Unverifiable accuracy: Without processing checkpoints, RTK/PPK maps cannot be measured for error.
  • Can be expensive: Requires specialized equipment and potentially software subscriptions.

 

 

Combining GCPs (w/ Checkpoints) and RTK/PPK - Recommended

  • Maximizes accuracy: GCPs provide ground truth, while RTK/PPK refines drone-derived coordinates.
  • Improves efficiency: GCPs can minimize the dependence on RTK/PPK in critical areas, optimizing data acquisition. Fewer GCPs are needed in combination with RTK/PPK to maximize accuracy.
  • Reduces errors: GCPs can identify and mitigate potential inaccuracies in RTK/PPK data.
  • Example map:Screenshot 2024-04-18 at 9.57.47 AM.png
    • 108 Acre Site flown with the Mavic 3 Enterprise w/ PPK at 200 Feet.
      • 6 GCPs and PPK used to make corrections.
      • 3 Checkpoints placed for validation.
    • Results:Screenshot 2024-04-18 at 10.02.29 AM.png

 

See article: Single GCP Processing for RTK and PPK captures

 

When to use both

High-precision projects: Land surveying, comparison to modeled data, precise volumetric calculations over time, or for highly accurate as-built data. Use when you need the highest accuracy possible.

 

Remember: The ideal approach depends on your project requirements, budget, and environmental factors. Consider a cost-benefit analysis and chat with us to determine the best combination for your specific needs.

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