Details for Benchmark: HL0421
N 37° 47.400 W 107° 40.367 (NAD 83)
Coordinates may not be exact. Altitude is ADJUSTED and location is SCALED. (more info)
- In SAN JUAN county, CO View Original Datasheet
- Q 439
- Marker Type:
- bench mark disk
- in rock outcrop
- Most reliable and expected to hold position/elevation well.
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Documented History (by the NGS)
|01/01/1985 by NGS (MONUMENTED)
|DESCRIBED BY NATIONAL GEODETIC SURVEY 1985
2.9 KM (1.8 MI) SOUTH FROM SILVERTON. 2.9 KM (1.8 MI) SOUTHERLY ALONG U.S. HIGHWAY 550 FROM ITS JUNCTION WITH STATE HIGHWAY 110 IN SILVERTON, AT A HIGHWAY PULLOUT, IN AN EXPOSED AREA OF BEDROCK IN A HIGHWAY CUT, AND 6.9 M (22.6 FT) WEST OF THE CENTERLINE OF THE HIGHWAY. THE MARK IS 0.2 METERS E FROM A WITNESS POST THE MARK IS ABOVE LEVEL WITH THE HIGHWAY.
|07/07/1991 by USPSQD (GOOD)
|RECOVERY NOTE BY US POWER SQUADRON 1991 (WLR)
RECOVERED IN GOOD CONDITION.
- The horizontal coordinates were scaled from a topographic map and have an estimated accuracy of +/- 6 seconds.
- The orthometric height was determined by differential leveling and adjusted by the National Geodetic Survey in June 1991.
- The geoid height was determined by GEOID99.
- The dynamic height is computed by dividing the NAVD 88 geopotential number by the normal gravity value computed on the Geodetic Reference System of 1980 (GRS 80) ellipsoid at 45 degrees latitude (G = 980.6199 gals.).
- The modeled gravity was interpolated from observed gravity values.