Why use this template
Ground control points are the single biggest lever on drone survey accuracy. Get the layout wrong and no amount of post-processing will save you. Get the layout right and a modern RTK drone plus PPK correction can deliver 15 to 25 mm horizontal and 20 to 35 mm vertical accuracy consistently.
This template covers the two things field surveyors need before they fly: how many GCPs to place and where, and what a residuals report should look like when the job is done.
Section 1. GCP planning rules of thumb
- Small site (under 5 ha): minimum 5 GCPs, one near each corner plus one centre
- Medium site (5 to 20 ha): minimum 6 to 8 GCPs distributed across the survey area
- Large site (20 to 100 ha): 10 to 15 GCPs with a denser ring near the edges where the block bundle is weakest
- Linear site (road, rail, river): GCPs every 150 to 300 m alternating sides of the alignment
- Vertical control: at least 20% of GCPs should be on features the block bundle cannot constrain easily (flat open ground, not verges or slopes)
- Check points: always hold back at least 20% of your control as check points (not used in adjustment)
Section 2. GCP observation protocol
- Observation method: CORSnet RTK rover with 60 second static occupation per GCP
- Minimum PDOP: 2.5 (retake if above 4.0)
- Fix type: integer fixed only (no float solutions accepted)
- Redundant observations: repeat each GCP at a different epoch and average
- Target: 300 mm x 300 mm chequerboard or painted cross on stable hard surface
- Record: photo of target in situ, rover height, tilt, timestamp and observer initials
Section 3. Residuals report format
| GCP ID | Role | Easting residual (mm) | Northing residual (mm) | Height residual (mm) |
|---|---|---|---|---|
| GCP-01 | Control | [e.g. 12] | [e.g. 9] | [e.g. 18] |
| GCP-02 | Control | |||
| CP-01 | Check |
Section 4. Pass / fail criteria
- RMSE horizontal on control points: 20 mm or better
- RMSE vertical on control points: 30 mm or better
- RMSE horizontal on check points: 25 mm or better
- RMSE vertical on check points: 40 mm or better
- Maximum single residual: 3 sigma of the sample (flag any outlier)
Section 5. Report sign-off
- Project reference, survey date, processing date
- Software and version used for bundle adjustment
- Coordinate system: Irish Transverse Mercator (EPSG:2157)
- Vertical datum: Malin Head (OSGM15 geoid model)
- Chief Remote Pilot signature and EASA operator ID
Need this customised for a specific project? If you are preparing a tender, condition survey, or project handover and need this tailored to your site, asset type, or regulatory context, we can usually turn a custom version around in a day. Talk to our team or browse the full Assets Hub for more templates.