# Checkpoint descriptions

D in P,N,E,Z,D is the survey Description, not a LAS classification. Example: `101,9980712.50,3302388.50,350.25,ASPHALT`; N/E/Z use confirmed native project units and datum. Codes imply neither units nor a Z offset.

| Exact starter code | Surface category | Pool |
|---|---|---|
| ASPHALT, CONCRETE | Hard / paved | NVA |
| BARE | Bare earth | NVA |
| SHORT_GRASS | Short grass | NVA |
| TALL_GRASS, BRUSH, FOREST | Vegetated | VVA |

Import assigns no categories. **Apply standard code guide** uses trimmed, case-insensitive exact tokens and fills only currently unmapped recognized descriptions. Unknown/blank descriptions and partial codes such as GRASS or ASPHALT_EDGE remain unmapped. Original CSV descriptions remain in the audit. Custom mappings, limits, tolerances and reasons remain editable and are preserved. The guide supplies no numeric defaults.

Residual = the final exported LandXML grid-TIN elevation at native E/N minus surveyed checkpoint Z, converted from native units to centimetres. It uses the same final DEM cell-centre faces and output smoothing state; no extrapolation or hole bridging. Description never changes elevation, ground classification, smoothing, fitting or the global ASPRS class.

One declared product vertical class controls checkpoint survey-quality eligibility and the pooled NVA combined-RMSE comparison. Combined RMSE = sqrt(residual RMSE² + documented checkpoint survey RMSE²). VVA combined RMSE is reported as found. There are no separate formal pavement, bare-earth or short-grass tolerances. Existing count, survey quality, independence, datum/distribution, bias/blunder and agreement requirements continue to govern a scoped ASPRS 2024 assessment.

An optional Description-specific **NVA group combined-RMSE limit** or **VVA empirical absolute-error P95 limit** is a project diagnostic, not an ASPRS point class. Optional individual absolute-error tolerance compares abs(residual), never causes automatic exclusion, and never substitutes for the pooled RMSE criterion. Excluded/unmapped rules are not assessed; entered values remain in the audit configuration. Unknowns, invalid rows and no-data require review.

The HTML report lists each actual D mapping, surface/pool, group metric and declared limit, individual tolerance and Description exclusion reason. JSON holds the immutable configuration snapshot; CSV preserves original rows and measured audit values. Report/calc version0.4, package0.5, classifier/native writer0.3 remain unchanged.