SiteLens moves coordinates between several distinct spaces. Understanding them is the key to using the tool correctly.
Building grid
The architect's coordinate space: lettered axes (A, B, C...) crossing numbered axes (1, 2, 3...), with offsets measured from the gridlines. It has no inherent relationship to the real world until you tie it to control points.
Projected (northing / easting)
The real-world planar system the city publishes control in — almost always a State Plane or UTM zone, identified by an EPSG code. Coordinates are a northing (Y) and easting (X) in the project's units.
Geographic (latitude / longitude)
Angular coordinates on the ellipsoid (WGS84). SiteLens converts to and from geographic so it can place the site on terrain and so you can cross-check against mapping tools.
Grid vs. ground
This distinction trips up many crews. Published northing/easting are grid coordinates — they live on a projection that slightly distorts distance. The tape or total-station distances you measure on site are ground distances. The combined scale factor relates the two.
SiteLens tracks the combined scale factor per project and lets you view or export coordinates as either grid or ground. Always know which one a number is.
Units
| Unit | Definition | Typical use |
|---|---|---|
| Meter | SI base unit | Most of the world; SiteLens internal canonical unit |
| US survey foot | 1200 / 3937 m (exact) | US legacy / State Plane datasheets |
| International foot | 0.3048 m (exact) | Newer US work and elsewhere |
Internally every coordinate is stored in meters. Conversion happens only at the edges — import, display, export — and the unit is always shown.
Next: Grid & Control Points.