2017-04-09

GT0292 "3926 1905"

This early 1900s U.S. Geologic Survey Benchmark is located a the Inyo County courthouse in the beautiful town of Independence, Ca. The mark is set in the westerly face the southerly balustrade of the front steps of the Courthouse.

The coordinates shown by the GPSr were dramatically different from the published coordinates to the tune of about 1250 feet horizontally. I imagine it was due to signal multi-path or signal shadow caused by the building. Interestingly, the elevation was only 143 feet. I would have expected more given the horizontal error.

Regardless of the coordinates or GPSr error, the goto description on the datasheet is clear and makes finding the mark easy.
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Found Details for Benchmark: GT0292
N 36°48.212', W 118°11.985' (NAD 83)
Altitude: 3786
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Published Details for Benchmark: GT0292
N 36°48.100', W 118°12.200' (NAD 83)
Altitude: 3929.89

Coordinates may not be exact. Altitude is ADJUSTED and location is SCALED.

Location: In INYO county, CA
Designation: 3926
Marker Type: survey disk
Setting: massive structures
Stability: Most reliable and expected to hold position/elevation well.

Documented History (by the NGS)
01 Jan 05 by USGS (MONUMENTED)

01 Jan 62 by NGS (GOOD)
DESCRIBED BY NATIONAL GEODETIC SURVEY 1962 AT INDEPENDENCE. AT INDEPENDENCE, AT THE COUNTY COURTHOUSE, SET VERTICALLY IN THE WEST-SOUTHWEST FACE OF THE SOUTH-SOUTHEAST ONE OF TWO BALISTRADES AT THE WEST-SOUTHWEST (MAIN) ENTRANCE, 15 1/2 FEET SOUTH-SOUTHEAST OF THE CENTER OF THE STEPS LEADING INTO THE BUILDING, 2.0 FEET ABOVE THE FIRST LANDING ABOVE THE GROUND, AND ABOUT 3 1/2 FEET ABOVE THE GROUND.

01 Jan 87 by NGS (GOOD)
RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 1987 RECOVERED IN GOOD CONDITION.

GT0292 "3926 1905" - Benchmark detail.
GT0292 "3926 1905" - Benchmark, GPSr, and coordinates shown.
GT0292 "3926 1905" - Benchmark setting in the southerly balustrade of the Inyo County Courthouse in Independence, Ca.
GT0292 "3926 1905" - The impressive entrance to the Inyo County Courthouse in Independence, Ca.
GT0292 "3926 1905" - The copper cladded doors at the entrance to the Inyo County Courthouse in Independence, Ca.
GT0292 "3926 1905" - Plaque on the Inyo County Courthouse in Independence, Ca.
GT0292 "3926 1905" -  The view from the steps of the Inyo County Courthouse in Independence, Ca.

2017-04-08

AE4848 "S 1164 RESET" 1997

I found near the entrance to the airport in Independence, Ca. as described and in good condition.  The mark is described as being "set in the top of a concrete post projecting 0.5 foot above the ground", but I didn't find the mark immediately as I expected.  Over time, topsoil had moved in and covered everything.  Thankfully, close calls to the fence and witness post showed me where to look.  After kicking the dirt around for a few minutes, the mark was exposed.  I covered it back up before I left.

The published altitude of the mark is 3903.7, but my GPSr initially showed and elevation of 4000+ feet.  There was good satellite coverage, but the thick tree cover probably caused some problems.  After a few minutes, the GPSr was able to settle down and show an elevation of 3900'. 
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Published Details for Benchmark: AE4848
N 36° 48.583 W 118° 12.267 (NAD 83)
Altitude: 3903.7

Coordinates may not be exact. Altitude is RESET and location is SCALED.

Location: In INYO county, CA (View Original Datasheet)
Designation: S 1164 RESET
Marker Type: vertical control disk
Setting: set into the top of a round concrete monument
Stability: May hold, but of type commonly subject to surface motion.

Documented History (by the NGS)
01/01/1997 by CADT (MONUMENTED)
DESCRIBED BY CALTRANS 1997 (KR) 0.4 MILE (0.6 KM) NORTHWEST FROM INDEPENDENCE, 0.45 MILE (0.72 KM) NORTHWEST ALONG US HIGHWAYS 395 AND 6 FROM THE COUNTY COURTHOUSE AT INDEPENDENCE. AT THE MAIN ENTRANCE TO THE INDEPENDENCE AIRPORT, IN A EAST-WEST ROW OF TREES, 111.5 FEET (34.0 M) EAST OF THE CENTERLINE OF THE HIGHWAY, 73.0 FEET (22.3 M) SOUTH-SOUTHEAST OF THE CENTER OF THE ENTRANCE OF THE AIRPORT, 85.0 FEET (25.9 M) EAST OF POWER POLE NO. XP4-102 WITH A GUY WIRE, 1.6 FEET (0.5 M) NORTH-NORTHEAST OF A FENCE, 1.6 FEET (0.5 M) SOUTH-SOUTHEAST OF A WITNESS POST, SET IN THE TOP OF A CONCRETE POST PROJECTING 0.5 FOOT (15.2 CM) ABOVE THE GROUND. N 88 DEGREES W 74.7 FEET (22.8 M) TO TOP OF FIRE HYDRANT, S 66 DEGREES W 111.5 FEET (34.0 M) TO POWER POLE NO. XP4-102 WITH GUY WIRE, N 56 DEGREES E 66.7 FEET (20.3 M) TO POWER POLE NO. M26380V WITH GUY WIRE.

AE4848 "S 1164 RESET" 1997 - Benchmark detail.
AE4848 "S 1164 RESET" 1997 - Benchmark and GPSr.
AE4848 "S 1164 RESET" 1997 - Benchmark setting and witness post.  The mark was found under 3 inches of topsoil.
AE4848 "S 1164 RESET" 1997 - Benchmark location setting and witness post.  The mark was found under 3 inches of topsoil.  View southeasterly.
AE4848 "S 1164 RESET" 1997 - Benchmark location setting and witness post.  The mark was found under 3 inches of topsoil.  View southwesterly.
AE4848 "S 1164 RESET" 1997 - Benchmark and GPSr.  View northeasterly toward the Independence Airport.
AE4848 "S 1164 RESET" 1997 - Benchmark coordinates and settled elevation.