Garmin maps are derived from vectorized USGS 1:100,000 topo maps.
Magellan maps are derived from the USGS DEM (Digital Elevation Model) points on a 90-meter grid.
Garmin USA Topo
Magellan Topo USA
USGS 1:96,000 Scale
Garmin BlueChart
Garmin WorldMap
1:24,000 Maps
Garmin USA Topo
Magellan Topo USA
USGS 1:24,000 (original) Scale
Garmin BlueChart
Note that the glacier at the GROUP-PHOTO has receded farther in the USGS map than the BlueChart