Metrology Department
 

Official Coordinates for SLAC M40

The official coordinates of the Master Control Station refer to the Antenna Reference Point (ARP) of the LEICA AT-504 GPS antenna. The ARP is located at the bottom of the preamplifier as indicated in the antenna diagram: 

  LEIAT504
  
                           +-------+                          <-- 0.1393
                         /     +     \                        <-- 0.1282 L2
                        |      +      |                       <-- 0.1093 L1
      +-----------------+-------------+------------------+    <-- 0.1020 TCR
      |                                                  |
      |                                                  |
      |                                                  |
      |                                                  |
    +-+--------------------------------------------------+-+  <-- 0.0380
    +-------------------+-------------+--------------------+  <-- 0.0350 BCR
                        |             |
                        |             |
                        +------x------+                       <-- 0.000  BPA=ARP
  
    <--                      0.3794                      -->
  

     ARP: Antenna Reference Point
     L1 : L1 Phase Center                   L2 : L2 Phase Center
     TCR: Top of Chokering                  BCR: Bottom of Chokering
     TGP: Top of Ground Plane               BGP: Bottom of Ground Plane
     TPA: Top of Preamplifier               BPA: Bottom of Preamplifier
     TOP: Top of Pole                        

  All dimensions are in meters.


The coordinates are geocentric XYZ triplets in the International Terrestrial Reference Frame 2000 (ITRF2000) geodetic datum as provided by the International Earth Rotation Service (IERS). They are updated on an as-needed basis.

Determined on Epoch X [m] Y [m] Z [m] Comments
2002-04-30 2002.22 -2703115.949 -4291767.428 3854247.948 old mount
2002-06-21 2002.36 -2703115.873 -4291767.294 3854247.829 new mount
2003-07-14 2002.90 -2703115.889 -4291767.281 3854247.836  

The current coordinates are also available in different datum definitions and with other representations.

Type Coordinate triplets for SLAC M40 at 2002.90 Datum
XYZ -2703115.889 m -4291767.281 m 3854247.836 m ITRF2000
φ λ h 37° 24' 59.45851" -122° 12' 15.34051" 63.689 m
XYZ -2703115.216 m -4291768.545 m 3854247.799 m NAD83
φ λ h 37° 24' 59.44353" -122° 12' 15.28996" 64.231 m  
NEH 603088.745 m 1849150.025 m 96.743 m  

For the datum conversion from ITRF2000 to NAD83 we used the transformation parameters as published by the National Geodetic Survey (NGS). The California State Plane coordinates Northing N and Easting E were computed with NGS's routine spsc83. The orthometric height H was derived from the ellipsoidal height h by using the GEOID99 geoid undulation value of N=-32.512m.

For the current epoch (2002.90) velocity values have been determined (using approximately 1.5 years of data). In the ITRF00 and NAD83 reference frames the velocities take the following values:

Type

Velocity of SLAC M40 at 2002.90

 Datum
VxVyVz -25.2 +/- 2.5 mm/a 24.2 +/- 3.9 mm/a 9.2 +/- 3.5 mm/a ITRF2000
VnVeVu 11.6 +/- 1.4 mm/a -34.2 +/- 1.2 mm/a 0.0 +/- 5.5 mm/a
VxVyVz -8.8 mm/a 24.9 mm/a 20.3 mm/a NAD83
VnVeVu 26.1 mm/a -20.7 mm/a -0.6 mm/a  

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Last update: March 08, 2007