Arc | Meters (approximate) | Used for |
---|---|---|
1 degree | 110 kilometers | |
7.5 arc minutes | 14 kilometers | Size of a traditional map "quad" |
30 arc seconds | 1 kilometer | Global elevation |
3 arc seconds | 90 meters | World-wide SRTM |
1 arc second | 30 meters | DEM from topo, USA SRTM |
1/3 arc second | 10 meters | DEM from topo |
1/9 arc second | 3.4 meters | Newer DEM from LIDAR |