Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Stage 3—Referencing the basemap to an external (global) coordinate system
Coordinates for a network of immobile geographic features, such as road intersections (▴), are collected using global positioning system (GPS) receivers. To improve precision and accuracy, the geometric mean of three GPS measurements taken at the same location defines the final coordinate for each road intersection. Roads (
); Study area boundary (
)
