Overview
After you record control points (CPs) during stationing, the Dusty App shows two tables under Station Information: Distance Errors and Station Errors. Together they tell you whether your control is good enough to print accurately, and they help you find and remove any control point that was mis-surveyed or mis-identified.
This article explains what each table measures, which one to use first when hunting for a bad point, and a step-by-step process for ending up with a clean, reliable station.
A note on tolerance: The acceptable error is set by your project — it is not a fixed number. It is typically between 1/16" and 1/4", depending on the type of work and how tight its accuracy requirements are. Throughout this article, "within tolerance" means within the limit your project has set. Set your tolerance before you start, and apply the same value in both tables.
The two tables at a glance
| Table | What it measures | Use it to… |
|---|---|---|
| Distance Errors | Distance between two control points in the CAD model and the actual distance recorded on the slab. | Find a mis-surveyed or mis-identified control point. |
| Station Errors | The maximum adjustment applied to each individual control point so the layout best-fits all of your recorded points. | Confirm the station is tight after you have removed any bad points. |
The two tables appear at different points in the workflow. The Distance Errors table populates as soon as you have recorded two control points. The Station Errors table becomes available after you have recorded at least three control points and pressed Station.
These tables describe two different stages. Distance Errors compare the distances you measured between recorded points against the CAD model — this happens before any alignment is applied, so it reflects your raw measurements. Stationing (pressing Station) is when the system applies the best fit: it rotates and shifts the whole layout as one rigid piece — it does not stretch or distort it — to sit as closely as possible on the points you kept. The Station Errors table is the result of that best fit.
What the columns mean
- X-Y Error — the horizontal error, measured in the plane of the floor. This is the number that drives layout accuracy, so it is the column you act on.
- Z Error (grayed out) — the vertical (elevation) error. When you are using Radio 2 with a level tracker, the system uses 2D stationing and Z values are shown for information only — they are not used in the accuracy calculation, which is why the column appears grayed out. On Radio 1, or when the tracker is not level, the system uses 3D stationing and Z does affect the result.
- Tilt (Station Errors table) — how level the tracker was. A green check means the tracker’s tilt is 1.5° or less.
How to remove bad control points
Work the tables in this order. Starting with the wrong table is the most common reason operators remove a good point and keep a bad one.
1. Start with the Distance Errors table
Distance Errors point straight at a mis-surveyed point. They are measured before any best fit is applied — you are simply comparing the distances between your recorded points to the model — so a distance error is a real disagreement in your measurements, not a side effect of stationing. (You can review this table after recording two points; you do not need to station first.)
2. Find the point that shows up again and again
A single bad control point disagrees with every point it is paired with, so it appears in multiple rows with high X-Y errors. The control point that keeps recurring across the high-error rows is your suspect. A point that is only high in a single pair is not enough to act on yet — the other point in that pair may be the real problem.
3. Remove one point, then look at the updated Distance Errors table
Deselect the single clearest offender and look at the updated Distance Errors table. You are not stationing yet — you are still just comparing measured distances, and the table refreshes as soon as you remove a point. Remove points one at a time so you do not over-trim. Repeat until every X-Y Distance Error is within your project tolerance.
4. Confirm with the Station Errors table
Once your Distance Errors are clean, press Station (you need at least 3 recorded points), then open the Station Errors table and confirm every X-Y Station Error is also within your project tolerance. The station should tighten after each removal.
⚠ Important: If a point shows a high Station Error (red) but its Distance Errors are clean, that is almost always real slab elevation variation (a Z effect), not a survey problem. Do not remove that point — it is horizontally good. This is also why Z is set aside under 2D stationing.
Do not remove a point you need for coverage
"Within tolerance" is the bar — not "lowest error." Layout accuracy degrades outside the area bounded by your control points, so a corner point that brackets your print area can be worth more than a lower-error point sitting inside it. A point with a slightly higher error that is still within tolerance and is needed to surround the print area should be kept.
If a point that you need for coverage is genuinely bad, re-survey it — do not just drop it.
⚠ If removing control points leaves you with fewer than 3 points, or the remaining points no longer surround the print area, request additional control points from the surveyor before printing.
When the station is good enough to print
Accept the station only when all of the following are true:
- At least 3 control points, and they are not all on a single straight line.
- Every remaining X-Y Station error — in both tables — is within your project tolerance.
- The control points surround the print area (not clustered inside it or on one side).
- Your widely spaced, far-edge points are still in the set — these do the most to keep a large print area accurate.
Moving to a new station
When you re-station, carry over shared control points from the previous station so the two stations line up. Carry over at least one shared point — two or more is strongly recommended. One shared point only locks position; two well-spaced shared points also lock orientation, which prevents the layout from rotating slightly between stations (a common cause of offset or shifted lines).
After re-stationing, reprint a line or point from the previous station. If it does not land within your project tolerance, review the Distance and Station Errors and reevaluate your control point selection before continuing.
Best practices
- Use more than 3 points. More points reduce the impact of any single bad point and improve the fit.
- Spread points wide and around the print area. Never place them all in a line or all on one side.
- Favor distance. A far point with a slightly higher error often performs better than a close point with a lower error, especially over a large print area.
- Diagnose with Distance Errors, confirm with Station Errors. Identify the bad point with Distance Errors; use Station Errors to verify the cleaned-up station.
- Bad control is a control issue, not a robot issue. High errors mean a point needs re-checking or re-surveying.