Control point errors change during the day because something has moved since you last stationed. Most often it's the laser tracker. A bump, vibration from nearby work, a loose tripod leg, or materials expanding and contracting as the temperature changes can each shift the error values you see when you station again. Small changes like this are normal.
What makes control point errors change during the day
| Cause | What happens | How to spot it |
|---|---|---|
| The laser tracker moved (most common) | Someone bumps the tripod, or vibration from equipment, other trades, or wind shifts it. The tracker is no longer where it was when you stationed, so its measurements no longer line up with your control. | The Dusty app alerts you after a verification check fails. See the next section. |
| Loose tripod legs | Legs or clamps that aren't fully tightened let the tripod settle or slide over time. | The tripod moves when you press on it lightly, or it's no longer level. |
| Temperature changes | Concrete, wood decking, and the tripod itself expand in heat and contract in cold. That changes the distances between the laser tracker and your control points by a small amount. | Errors shift more on days with big temperature swings, or after the work area heats up in the sun. |
| Faulty equipment | A damaged laser tracker, tripod, or reflector can give readings that don't repeat. | Errors keep changing even though the setup is stable and nothing has been bumped. Swap in the backup reflector to rule out the reflector, then contact Dusty Support. |
How the verification reflector catches tracker movement
The verification reflector is a fixed target that you tape down 10 to 50 feet from the laser tracker. Record it in the Dusty app under the Setup. While the FieldPrinter prints, the laser tracker checks itself against the verification reflector about every 15 minutes. If the tracker has moved relative to the reflector, the Dusty app alerts you.
That alert means layout printed after the tracker moved may be inaccurate. For more information, see How to Verify Control Point Accuracy After Stationing. For setup steps, see How to Set Up and Use the Verification Reflector.
How to keep errors consistent through the day
- Tighten every tripod leg and clamp, and level the tripod before you station.
- Always use the tripod base, and add weight to the tripod if it could slide.
- Set up away from foot traffic and vibrating equipment.
- Set up in the shade when you can, and keep the tripod off hot slabs.
- Record the verification reflector at every station.
- Station on 6 to 8 control points when possible, so one point that moved has less effect on the result.
When the change isn't small
If error values jump a lot between stationings, or more than half your control points show high errors, the cause is more likely the control itself than the laser tracker. See Troubleshooting High Error Values During Stationing.