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Details for Benchmark: AI7208

N 38° 49.917 W 077° 02.383 (NAD 83)

Altitude: 6.18

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

Location:
In C OF ALEXANDRIA county, VA View Original Datasheet
Designation:
BOUNDARY WITNESS MK 12 DC VA RM 4
Marker Type:
reference mark disk
Setting:
set into the top of a round concrete monument
Stability:
May hold, but of type commonly subject to surface motion.

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Found as described - coordinates are quite a bit off, this is closer to the boat launch area; just as I found it a truck came up and parked in front of the no parking.

[Photos:]
photoDSC00255
photoConcrete holders for old sign

Found as described in good condition. With back to the water, the E trash barrel is the one on the left. The bulletin board that used to stand between the trash barrels has been removed, but the concrete postholes for it remain. Note: the parking lot has been repaved recently and it appears that the primary mark (AB2003 BOUNDARY WITNESS MARK 12 DC VA RESET) has been covered by asphalt.

[Photos:]
photoAI7208 mark: BOUNDARY WITNESS MK 12 DC VA RM4
Mark and GPSr. Difficult to get a good photo leaning over into trash bin holder. I probably looked like one of the squirrels I see digging in the garbage cans while I'm on my morning bike rides through the parks nearby...
photoAI7208 area S: BOUNDARY WITNESS MK 12 DC VA RM4
View to the S, mark is at lower center, underneath trash barrel holder (trash barrel has been removed and placed to the left) indicated by notebook. Trash barrel holder has a sign attached ("RIGGING ONLY - NO TRAILER PARKING).

This reference mark was found as described.
The station is under about an inch of dirt.

[Photos:]
photoReference mark 4 in Alexandria, Virginia
The reference mark disk. The white bar is from overexposure through the gap between the decorative cover around the trash can.
photoReference mark 4 is under the left trash can in Alexandria, Virginia
Under the trash can on the left is Reference mark 4.
photoReference mark 4 in Alexandria, Virginia
View of the reference mark disk in the wooden supporting barrel holder. The disk is in the left side of the bottom.

Bulletin board with flanking trash cans found near launch ramp as described. I lifted out the eastern (left) trash can, but what was underneath was a bit too disgusting for me to go after, especially without any tools or gloves on me. Probably there for a heartier soul to recover.

Documented History (by the NGS)

01/01/1965 by CGS (MONUMENTED)
08/01/2000 by NGS (GOOD)
DESCRIBED BY NATIONAL GEODETIC SURVEY 2000 (RWA) 0.6 MILE (1.0 KM) NORTH ALONG G W PARKWAY FROM THE JUNCTION OF SLATERS LANE IN ALEXANDRIA TO THE JUNCTION OF MARINA DRIVE FOR THE WASHINGTON SAILING MARINA, THENCE 0.05 MILE (0.08 KM) EAST ALONG MARINA DRIVE TO A Y JUNCTION, THENCE LEFT 0.2 MILE (0.3 KM) NORTHEAST ALONG PAVED ROAD TO A T JUNCTION AND SECURITY GATE, THENCE 0.1 MILE (0.2 KM) EAST TO A T JUNCTION, THENCE LEFT (NORTH) FOR 0.05 MILE (0.08 KM) ALONG PAVED ROAD TO MARK ON LEFT, AT A BULLENTIN BOARD WITH TRASH BARRELS ON EACH SIDE, AND MARK IS UNDER THE EAST ONE OF THE TWO, LIFT TRASH BARREL OUT OF A WOODEN SUPPORTNG BARREL HOLDER, 63.0 FEET (19.2 M) NORTH OF LAMP POST, 116.4 FEET (35.5 M) SOUTHWEST OF THE WEST ONE OF THREE BOAT HOISTS, 69.0 FEET (21.0 M) WEST OF STATION NO 12, 66.9 FEET (20.4 M) NORTHWEST OF RM 3 AND 3 FEET (0.9 M) SOUTHWEST OF EDGE OF PARKING LOT.

Control Text

  • 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 November 2000. No vertical observational check was made to the station.
  • 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.

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