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Details for Benchmark: AB7677

N 37° 44.005 W 122° 29.817 (NAD 83)

Altitude: 77.7

Coordinates may not be exact. Altitude is LEVELING and location is ADJUSTED. (more info)

Location:
In SAN FRANCISCO county, CA View Original Datasheet
Designation:
HPGN D CA 04 GE
Marker Type:
survey disk
Setting:
aluminum alloy rod
Stability:
Probably hold position/elevation well.

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Es macht spass diese Benchmarks zu suchen.

#34

[Photos:]
photoAB7677

Found access cover, but screw was cross threaded so cover would not open.

Access cover is from the north light post (E0/1), south light post cross, and house, however house address is 379 'Lakeshore' Dr, not Skyline.

[Photos:]
photo029
Looking North (light post (E0/1).
photo027
Looking South
photo028
Flush with surrounding area.
photo023
Access cover screwed DOWN.

Found while doing some Geocaching in the San Francisco area.

[Photos:]
photoHockeyHiker19 taking a picture of the BM
photoThe disk in the ground

Found in good shape.

[Photos:]
photoAB7677

Found, in good conditions. I pass around this place everyday

Coordinates were exact.

[Photos:]
photoThe cover
photoThe Disk
photoLooking West

Disk is there as described.

The description is good and the access cover was not screwed shut (as it really should have been) so the disk could be viewed by just lifting the access cover. There was a circle of red marking paint around the access cover so apparently Caltrans has been using the marker recently.

Note that this marker had been set by GPS. Some of the GPS surveying equipment can apparently get locations to within less than an inch. Of course, the reading time may require from several hours to the better part of a day, and the equipment costs on the order of $10,000.

[last edit: 6/15/2003 8:48:58 AM PST]

[last edit: 6/15/2003 8:50:54 AM PST]

Documented History (by the NGS)

01/01/1994 by CADT (MONUMENTED)
DESCRIBED BY CALTRANS 1994 (DAN) THE STATION IS LOCATED NEAR THE INTERSECTION OF SKYLINE BLVD (STATE HIGHWAY 35) AND SLOAT BLVD AT THE NORTHEAST CORNER OF THE SAN FRANCISCO ZOO, ABOUT 6 MI (9.7 KM) SOUTHWEST OF DOWNTOWN SAN FRANCISCO. TO REACH THE STATION FROM THE INTERSECTION OF SLOAT BLVD (STATE HIGHWAY 35) AND 19TH AVE (STATE HIGHWAY 1) , GO WEST ON SLOAT BLVD, CROSSING OVER SUNSET BLVD, FOR 1.2 MI (1.9 KM) TO THE Y-INTERSECTION WITH SKYLINE BLVD (STATE HIGHWAY 35) . BEAR LEFT AND GO SOUTHWEST ON SKYLINE BLVD FOR ABOUT 165 FT (50.3 M) TO THE STATION ON THE LEFT IN THE RAISED MEDIAN ISLAND AT POST MILE 1.8. THE STATION IS A SURVEY DISK ENCASED IN PVC PIPE WITH ACCESS COVER SET IN CONCRETE FLUSH WITH THE SURFACE OF THE RAISED MEDIAN ISLAND, ABOUT 165 FT (50.3 M) SOUTHWEST OF THE INTERSECTION OF SKYLINE BLVD AND SLOAT BLVD, 118.5 FT (36.1 M) NORTHWEST OF THE NORTHWEST CORNER OF THE HOUSE AT 379 SKYLINE BLVD, 96.4 FT (29.4 M) NORTHEAST OF A LIGHT POST AT THE SOUTH END OF THE MEDIAN ISLAND, 74.3 FT (22.6 M) SOUTHWEST OF LIGHT POST E0/1 AT THE NORTH END OF THE MEDIAN ISLAND, 65.0 FT (19.8 M) WEST OF AND ACROSS THE NORTH-BOUND LANES OF SKYLINE BLVD FROM LIGHT POST 0/6, 18.4 FT (5.6 M) EAST OF THE WEST CURB OF THE MEDIAN ISLAND AND 7.3 FT (2.2 M) WEST OF THE EAST CURB OF THE MEDIAN ISLAND. THE DISK IS 0.3 FT (0.1 M) BELOW THE LID OF THE ACCESS COVER. THIS STATION WAS OCCUPIED AS PART OF A CALIFORNIA HPGN DENSIFICATION SURVEY IN 1994.

Control Text

  • The horizontal coordinates were established by GPS observations and adjusted by the National Geodetic Survey in October 1996. The horizontal coordinates are valid at the epoch date displayed above. The epoch date for horizontal control is a decimal equivalence of Year/Month/Day.
  • The orthometric height was determined by differential leveling. The vertical network tie was performed by a horz. field party for horz. obs reductions. Reset procedures were used to establish the elevation.
  • The X, Y, and Z were computed from the position and the ellipsoidal ht.
  • The Laplace correction was computed from DEFLEC99 derived deflections.
  • The ellipsoidal height was determined by GPS observations and is referenced to NAD 83.
  • The geoid height was determined by GEOID99.

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