Am I blind, or is this antenna not in the NGS list:
ASH700936C_M SCIT
This is an older Ashtech antenna that has been on this particular CORS (YBHB) since 1999.
SHG
Hmmmmm...something stinks here!
As you pointed out, the Site Log indicates that the original antenna got a SCIT Radome in 1999:
4.1 Antenna Type : ASH700936C_M NONE
Serial Number : 12414
Antenna Reference Point : BPA
Marker->ARP Up Ecc. (m) : 0.0531
Marker->ARP North Ecc(m) :
Marker->ARP East Ecc(m) :
Alignment from True N : 0
Antenna Radome Type : NONE
Radome Serial Number :
Antenna Cable Type :
Antenna Cable Length :
Date Installed : 1996-10-24T00:00Z
Date Removed : 1999-07-08T20:36Z
Additional Information :
4.2 Antenna Type : ASH700936C_M SCIT
Serial Number : 12414
Antenna Reference Point : BPA
Marker->ARP Up Ecc. (m) : 0.1269
Marker->ARP North Ecc(m) :
Marker->ARP East Ecc(m) :
Alignment from True N : 0
Antenna Radome Type : SCIT
Radome Serial Number : 00207
Antenna Cable Type :
Antenna Cable Length :
Date Installed : 1999-07-08T22:39Z
Date Removed :
Additional Information : SCIGN adaptor 0122 and dome added
And I can't find that particular Antenna/Radome combination in either the NGS Antenna Calibration list, OR in the latest IGS file (igs08_1785.atx) either (current as of 3/28/2014).
Even scarier, is that the NGS Coordinate sheet says:
| -------------------------------------------------------------- |
| The D/M element, milled chokerings, -radome antenna |
| (Antenna Code = ASH700936C_M NONE) was installed on 24Oct1996. |
| The L2 phase center is 0.029 m above the L1 phase center. |
| PID = AE1836 |
| |
| |
| IGS08 POSITION (EPOCH 2005.0) |
| Computed in Aug 2011 using data through gpswk 1631. |
| X = -2576447.929 m latitude = 41 43 53.96002 N |
| Y = -4011576.537 m longitude = 122 42 38.64765 W |
| Z = 4224117.143 m ellipsoid height = 1065.899 m |
| |
| The IGS08 VELOCITY of the L1 PC is the same as that for the ARP. |
| |
| |
| NAD_83 (2011) POSITION (EPOCH 2010.0) |
| Transformed from IGS08 (epoch 2005.0) position in Aug 2011. |
| X = -2576447.202 m latitude = 41 43 53.94585 N |
| Y = -4011577.737 m longitude = 122 42 38.59315 W |
| Z = 4224117.107 m ellipsoid height = 1066.335 m |
| |
| The NAD_83 (2011) VELOCITY of the L1 PC is the same as that for the ARP. |
|_____________________________________________________________________________|
I think you should shoot an Email of to the NGS about this one.
Loyal
E-Mail sent, thanks for confirming that I wasn't completely loosing my mind!
SHG
Here is the NGS reply:
Looks like a SCIT dome was added in July of 1999.
As you stated this particular dome/antenna combination has not been calibrated.
When there is no calibration available the NONE configuration should be used.
So, there is a CORS for you with an un-calibrated antenna, That isn't what I wanted to hear!
SHG
Shelby-
I just sent you a PM...
Brian
> So, there is a CORS for you with an un-calibrated antenna, That isn't what I wanted to hear!
It's probably not a big deal, though. Look at the L1 phase center offsets for the 700933C_M, a very similar antenna (N E U, values in mm):
NONE 0.28 -0.67 89.35
SCIS 0.68 -0.67 87.35
SCIT 0.88 -0.97 88.45
SNOW 0.38 -0.57 89.25
The corresponding available values for the 700936C_M:
NONE 0.30 -0.62 90.74
SNOW -0.12 -0.46 90.36
I think you can use the NONE radome model and be within a millimeter or two, well within the noise level of the measurements.
Yes that probably works, I am just a bit surprised that this got accepted into the NGS CORS with a NON standard antenna installation, point is ALWAYS check your antenna info, it isn't always correct! I have an e-mail into the owner of the CORS to see what they say. It wouldnt be a surprise to find they have some other antenna actually installed!
SHG
