Glossary
The terms Backsight uses, in plain words.
4 min read
Coordinates and heights
| Term | Means |
|---|---|
| CRS | Coordinate reference system, the grid your numbers are on |
| Datum | The reference frame the grid is tied to, such as NAD83(CSRS) |
| EPSG code | A number identifying a published coordinate system exactly |
| Epoch | The moment a coordinate refers to, for frames that move |
| Geoid model | A model of the geoid, needed to turn GNSS heights into orthometric ones |
| Ellipsoidal height | Height above the mathematical ellipsoid; what GNSS measures |
| Orthometric height | Height above the geoid; what drawings use |
| Grid | A projected coordinate system, measured on the plane |
Drawing and surfaces
| Term | Means |
|---|---|
| TIN | Triangulated irregular network, a surface made of triangles |
| Breakline | A line the triangulation must follow: a curb, ridge or invert |
| Contour | The intersection of the surface with a level plane |
| Spot elevation | The surface's height at one point |
| Description key | A rule matching a field code to a symbol |
| Figure | Linework drawn from coded points |
| Linetype | A named dash pattern, sized in millimetres on the sheet |
| Annotation scale | The plot scale text is sized for |
Point clouds and drone
| Term | Means |
|---|---|
| LAS / LAZ | The standard point cloud formats; LAZ is LAS compressed |
| Classification | The ASPRS class on each point, ground, vegetation, building |
| SMRF | Simple Morphological Filter, the ground classifier Backsight uses |
| Orthophoto | An aerial image corrected so it measures like a map |
| Tie point | A feature matched between overlapping photos |
| Ground control point | A surveyed target used to check or georeference a flight |
Output
| Term | Means |
|---|---|
| Sheet | A page set up to plot: size, scale, title block, panels |
| Viewport | The window on the sheet showing the drawing |
| Template | A saved sheet design your office starts from |
| Reproducibility id | A short code identifying exactly which calculation produced a result |
| Checksum | A fingerprint of a written file, so you can prove it is unchanged |
Read next
- Choosing a coordinate systemThe one decision everything else rests on, and how to be sure you have it right.
- Building a surfaceTriangulate points into ground you can contour, measure and stake from.
- Ground classification: keeping the file's, or classifying it hereThree ways to get ground points out of a cloud, what the classifier actually does, and how to set it.
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