Calibration & benchmarks

Two words that mean two different things:

• A benchmark is a physical spot you can drive back to — the field entrance, a culvert headwall, a fence corner — that the app has recorded with its position and ground elevation.
• Calibrating is telling the app what your elevation is right now, by standing on something whose elevation is known: a benchmark, or a point on a survey / design you recorded earlier. It produces one hidden number (the offset between raw GPS and your job's elevations); you never need to see or type it.

RTK bases get moved between visits, so the raw GPS elevation of the same spot changes from day to day. Calibrating puts today's readings back into the frame your surveys and designs live in.

The BM badge (top stats bar) is the Calibrate door. Its colour is the status:

• Green — calibrated in this session; the sheet says to what ("Calibrated to benchmark "North gate" · 4 min ago").
• Amber — the app restored last session's calibration when it started. It is applied, but nobody has checked it since (the base may have moved). Recalibrate before working.
• Grey — not calibrated; elevations are raw GPS.

Calibrating (any workflow)

Tap the BM badge. The Calibrate Elevation sheet lists what you can calibrate to right now — one row each, nearest first:

• A benchmark — yours (cyan flag) or, in Land Forming, an AGD Design BM pin. Tap it: a drive-to card guides you in — Drive 23 ft to the benchmark (blue) → Almost there (amber, within ~10 ft) → On the benchmark — lower blade and calibrate (green). Lower the implement, hold still, tap Calibrate; the app averages 5 seconds of RTK. Calibrating while still metres away asks you to confirm — you'd be assigning the benchmark's elevation to wherever you happen to be.
• Loaded survey — drive to an unchanged point along the surveyed route; the row shows the nearest point's distance. Lower the implement, tap Calibrate (5 s average).
• Loaded design — same, using the design's terrain points. On a section already cut to grade, switch Surveyed ground → Design grade inside that row so the app uses the design elevation there (it refuses if you're more than 50 m off the design line: Too far from the design line — move onto the run first).

If none of those exist yet the sheet says so and points you at Manage benchmarks. Advanced (collapsed) holds the rare cases — type a known elevation, zero to current GPS, clear — each with a confirmation. Details shows the offset value and source for support calls.

Setting a benchmark

Tap the BM badge → Manage benchmarks → Set Benchmark here. Park on a repeatable spot, lower the implement to the ground, name it (the app suggests "BM 1", "BM 2", …), and hold still 5 seconds. A green Benchmark saved confirms it, the app is now calibrated to it, and it appears on the map as a cyan flag. Rename, delete and move-to-field live in the same panel. Surveys, designs and jobs you save from here on remember which benchmark they were aligned to.

Field Mode

With Fields on (Settings → Fields), benchmarks belong to the field, and the app drives the routine for you:

• Entering a field that has a benchmark and you haven't calibrated to it this session → Calibrate to this field's benchmark "North gate" (130 m) — tap Go and the sheet opens on its drive-to card. Later dismisses it for this session.
• Entering a field with no benchmark → Set a benchmark for this field? — Set Benchmark opens the panel ready to record. Once per field per session.
• Loading a survey / design / job from an earlier session: if you're calibrated to the field's benchmark and the file was saved aligned to that same benchmark, nothing is asked — it already lines up. If the file was aligned to a different benchmark, or recorded before the benchmark existed, the Calibrate GPS? prompt appears and says why.

Recommended routine per field: set the benchmark at the gate on day one; every return visit, park on it and tap Go → Calibrate. Everything you survey, design and grade in that field then matches, day after day and base after base.

Without Field Mode

The app does not push benchmarks. A new survey asks only for blade height. Loading a survey / design / job from an earlier session shows Calibrate GPS? once — drive to a point on it and calibrate, or Skip if the base has not moved. You can still set a benchmark any time via BM badge → Manage benchmarks; it works exactly as above.

When you need to calibrate — you loaded work from another session; the RTK base has moved, been replaced or rebooted; the badge is amber; surveyed elevations don't match what the machine reads on undisturbed ground. When you don't — you surveyed and started grading in the same session on the same base. There is no time-based stale detection beyond the amber restored state — recalibrating when the RTK session changes is on you.