Survey Track: Geology, Geophysics, Mapping and Core · Module 3 of 4 · about 15 min
Where exactly: GNSS, datums and lidar
GNSS is the general term for satellite positioning systems, including GPS. A phone gets meters of accuracy. Survey-grade receivers using real-time kinematic (RTK) corrections from a base station or network can reach centimeter-level accuracy.
Every coordinate is tied to a datum, a reference model of the Earth. In the U.S., NOAA's National Geodetic Survey (NGS) maintains the National Spatial Reference System, including the horizontal and vertical datums used for official work. Mixing datums is a classic way to put a drill hole in the wrong spot by meters.
Lidar sends laser pulses and times their return to build 3D point clouds. Flown from aircraft or drones, it can map ground under trees and measure stockpile volumes. USGS's 3D Elevation Program (3DEP) is collecting high-quality lidar over the U.S. and makes it public.
Mapping also happens on other planets. The HiRISE camera on NASA's Mars Reconnaissance Orbiter, run from the University of Arizona, takes high-resolution images that teams use to make terrain models of Mars.
Sources
Module quiz
5 questions, 4 correct to pass. You'll see what you missed and why, and you can retake it.