Every result in the app comes with an estimate of how far off it might be, so you can judge whether it is good enough for the job.
What to expect
- Points placed on the map: as good as the imagery under them. Satellite imagery is usually within a few meters, sometimes more in hilly or rural areas.
- Phone GPS: a few meters under open sky, worse near buildings and trees.
- RTK receiver with corrections: about 1–2 cm. See What you need for centimeter accuracy.
The ± figure
GPS results show an uncertainty, such as ≈ ±3% based on recorded GPS accuracy, worked out from the accuracy the phone or receiver reported for each point. Measurements recorded with GPS also show a GPS quality summary: a rating of Good, Fair or Poor, the average and worst accuracy, how many location points were used, and how many were ignored.
GPS quality requirement
Settings → GPS quality requirement decides which fixes are good enough to keep:
- Strict keeps only the most precise fixes; best for small areas.
- Balanced suits most fields and lots.
- Relaxed accepts weaker fixes, for poor sky view where Strict would keep too few.
The setting shows the exact thresholds for each choice.
Getting a better result
- Record GPS points outdoors with a clear view of the sky, and walk steadily.
- Use Mark each corner with GPS for straight sides: each corner is averaged from several fixes.
- On the map, zoom in before placing points.
Not a legal survey
The app is a measuring and estimating tool. Even with RTK, do not use it to establish property lines, settle boundary disputes, or replace a licensed surveyor.