Grass Valley--Nevada City (CA)

Survey type M-Dz (magnetic; digitized from contour maps)
Flown by U.S. Geological Survey
Date flown 09/67
Line spacing 0.8 (km)
Altitude 1067 (m) by barometer measurement
Total distance 828 (km)
References
Counties Butte - Nevada - Sierra - Yuba
Overlapping surveys

Data: Magnetic (M-Dz)