Grid length differs from geodetic length based on what correction factor?

Grid length and geodetic length are two concepts in geodesy that account for differences in measurement due to the curvature of the Earth and the projection of the Earth's surface onto a plane. The correction factor that addresses this discrepancy is the scale factor.

The scale factor is used to convert measurements from a grid system (such as a Cartesian coordinate system) to geodetic coordinates (which account for the Earth's curvature). When measurements are made on the ground and projected onto a grid, the length may differ due to the scale of that grid relative to the real-world distances on the Earth's surface. The scale factor effectively adjusts for these differences, allowing for accurate calculations of distances and areas when using grid coordinates.

Thus, when converting from grid length to geodetic length, incorporating the scale factor ensures that all measurements are consistent and correctly represent the real distances involved.