Sutter's Mill Question… (Topographic Maps)
As given in “Sutter's Mill Question..” at:
Dennis Miller asked:
“For my personal edification, what is the name of
the USGA Quadrangle map you are using. I need
to start another strewn field map, with itty bitty
dots, so far.
1. freewu2000 at yahoo.com replied:
“In Placerville I picked up 15 min topomaps named
Coloma. Also Pilot Hill to the west for where the big
one are speculated to be.”
and 2. Dennis Miller replied:
“Thanks for the map information. I did go to USGS and
ordered Coloma and Pilot Hill topos. The Coloma
(#328961) map is a 2012 aerial map.”
For GIS-minded people, free georeferenced 1:24,000
scale topographic map mosaic for all of El Dorado
County, California can be downloaded from the USDA
Natural Resource Conservation Service Geospatial
Datagateway at http://datagateway.nrcs.usda.gov/ .
For thedownloading the to the “Order by County/Counties” at:
From the above link a person can get free 1. Digital
Raster Graphic Topographic Map County Mosaic by
the NRCS, 2. and 2. high-resolution aerial imagery for
2009 and 2010. Both of these are georeferenced.
Finally, National Elevation Dataset, 3-meter resolution,
is available for download.
Individual georeferenced digital raster topographic
maps are available for free from the Cal-Atlas geospatial
clearinghouse at http://atlas.ca.gov/download.html
and the Cal-Atlas: Imagery Download Tool at
http://atlas.ca.gov/imagerySearch.html . For finding
the topographic maps check /choose the DRG data
layer in the "Download Tool" menu
Coloma 1:24,000 topographic map is “DRG O Series o38120g8.”
Pilot Hill 1:24,000 topographic map is “DRG O Series o38121g1.”
There is a choice of either collared (untrimmed) or
collarless (trimmed) DRGs (Digital Raster Graphics)
for the topographic maps.
I have loaded the individual DRGs for my field areas
into the company Ipad and used available apps to keep
track of my location as a blue dot on the DRG base I
moved around doing fieldwork. The same can be done
with many GPS units or other portable electronics.