Local Cartesian-plane idealization only—not a survey, navigation, geotechnical, construction, route, or safety determination. Verify coordinate frames, units, terrain, and decisions with qualified professionals.

ModeHorizontal unitVertical unitPoint elevation ± uncertainty

Points CSV/text: x,y,z in one local Cartesian coordinate frame

Point mode fits z = a·x + b·y + c after centering x/y/z. x and y must use one horizontal unit and z one vertical unit. Aspect is downhill bearing atan2(east, north), clockwise from local +y, normalized to 0–360°. Flat planes have no aspect.

Per-point residuals

Observed and fitted point elevations
Point	x	y	z	Fitted z	Residual

Contour Slope & Aspect Calculator

Per-point residuals

Method and diagnostics