Check a Survey for Duplicate Points and Level Busts
Last updated 26 September 2026
Catch the mistakes that survive a visual check before you send the file: points shot twice, points on top of each other, levels that jump.
Why check
Most survey mistakes look fine on a map: a point stored twice under two names, a shot taken with the wrong target height, a row pasted twice. They show up later, as a wrong volume or a level that doesn't make sense on the drawing. A minute of checking before you send the file is cheaper.
Run the checks
- Load your points in the web app or the Windows app and choose the grid.
- Open Quality checks in the section list. The checks run on their own and update as you edit. Four cards show how many they found: same point twice, almost touching, odd levels and no level.
- Everything found is listed under the cards with the station names, so you can fix the rows or accept them.
What it looks for
- Duplicates: two rows with the same coordinates to the millimetre — usually the same point stored twice, or a row pasted twice. Both names are listed.
- Points too close: points nearer to each other than the distance you set (0.10 m to start with) but not identical. On a detail survey this is often a re-shot point, or a point stored before the prism settled.
- Level jumps: a level that differs from the ground around it — the middle value of the points within 25 m — by more than the limit you set (1.5 m to start with). It compares with the neighbours, not with the whole job, so a sloping site doesn't fill the list. It needs at least four neighbours to judge. A wrong target height or a shot on top of a wall shows up here.
- Rows with no level. A sheet shot with no levels at all is reported once, not once per row.
Setting the limits
- Points closer than: raise it for a topographic survey at 5 m spacing; lower it for setting-out checks where two pegs can be 50 mm apart.
- Level differs from neighbours by: 0.3–0.5 m suits a flat site or a road; keep it higher on rough ground, embankments and walls, where real changes of level are large.
Where the results go
The survey report (PDF) includes the checks with their counts, so the client can see what was checked. Use design comparison as well when you have design coordinates to check against.
Try it with your own sheet