Jim Frame
Well-Known Member
I don't know if this belongs in the T-LS forum or the J-Field forum, but here goes:
When using the California Real Time Network in my T-LS, I have the Base Reference Frame set to NAD83(2011). According to the CSRC mountpoint document, CRTN stations are referenced to NAD83(2007) Epoch 2011.00. I've been assuming that the differences between these reference frames won't introduce enough error to worry about. However, I'm seeing a significant difference between the CRTN published position of the mountpoint I most often use (UCD1, PID AI4467) and the position reported by the T-LS.
The CRTN source document shows UCD1 as:
38 32 10.449957 121 45 4.380424 0.0915
But when I press the Stats button on the T-LS when connected to UCD1, it shows the base at
38 32 10.45142 121 45 04.38223 0.0851
This amounts to roughly -0.15' N, -0.18' E, and 0.02' EH. I'm not concerned about the height difference, because it's so small and because UCD moves more than that vertically anyway, but the horizontal is disturbing.
In an effort to figure this out, I connected to UCD via BNC and converted the XYZ position in the RTCM message to lat/long via the NGS online tool:
=================================================================
X (Meters) Y (Meters) Z (Meters) ELLIPSOID
INPUT = -2628825.7516 -4247933.4662 3952176.6501 GRS80
=================================================================
LATITUDE LONGITUDE ELLIP_HT ELLIPSOID
------------- -------------- ---------- ---------
N383210.44996 W1214504.38043 0.0914 GRS80
Thus the RTCM message position substantially agrees with the CRTN published position.
Why is the T-LS reporting such a different position? Is there a conversion going on that I'm not taking into account, or is my assumption about reference frame parameters off base?
When using the California Real Time Network in my T-LS, I have the Base Reference Frame set to NAD83(2011). According to the CSRC mountpoint document, CRTN stations are referenced to NAD83(2007) Epoch 2011.00. I've been assuming that the differences between these reference frames won't introduce enough error to worry about. However, I'm seeing a significant difference between the CRTN published position of the mountpoint I most often use (UCD1, PID AI4467) and the position reported by the T-LS.
The CRTN source document shows UCD1 as:
38 32 10.449957 121 45 4.380424 0.0915
But when I press the Stats button on the T-LS when connected to UCD1, it shows the base at
38 32 10.45142 121 45 04.38223 0.0851
This amounts to roughly -0.15' N, -0.18' E, and 0.02' EH. I'm not concerned about the height difference, because it's so small and because UCD moves more than that vertically anyway, but the horizontal is disturbing.
In an effort to figure this out, I connected to UCD via BNC and converted the XYZ position in the RTCM message to lat/long via the NGS online tool:
=================================================================
X (Meters) Y (Meters) Z (Meters) ELLIPSOID
INPUT = -2628825.7516 -4247933.4662 3952176.6501 GRS80
=================================================================
LATITUDE LONGITUDE ELLIP_HT ELLIPSOID
------------- -------------- ---------- ---------
N383210.44996 W1214504.38043 0.0914 GRS80
Thus the RTCM message position substantially agrees with the CRTN published position.
Why is the T-LS reporting such a different position? Is there a conversion going on that I'm not taking into account, or is my assumption about reference frame parameters off base?