Including Original "Paul H. Letters" Copyright © 1996-2018 Paul V. Heinrich - All rights reserved.

Saturday, 5 May 2012

Sutter's Mill Question… (Topographic Maps)

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 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 .
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
and the Cal-Atlas: Imagery Download Tool at . 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.

Best wishes,

Paul H.