CRTN Mountpoint Position Discrepancy

Jim Frame

Active Member
I noticed some vertical anomalies in a couple of recent projects, and when I checked the data recorded by my Triumph-LS for the base position I see that it changed sometime between January 14 and February 12. I'm trying to figure out if the problem lies with my receiver or the caster stream. Below are a couple of before-and-after screenshots for the same CRTN mountpoint (UCD1):

t.png




t1.png


For what it's worth, the differences between the more recent values and the published positions are almost exactly a foot vertical and just over a meter horizontal. Coincidental numbers, probably, but they caught my eye.

I checked my setup to make sure I don't have any base shift going on (all zeroes). Does J-Field massage the base position at all, or is the displayed base position coming directly from the stream?
 

Jim Frame

Active Member
NAD83(2011) is what it's currently set to, and to my knowledge I haven't changed that since I originally set it up.
 

Jim Frame

Active Member
Your most recent coordinates match the coordinates from the Station List published on March 12, 2018:
The station list shows an EH of -0.015 m, which is -0.049 foot. That jives with the December shot shown above, but not with the February shot.
 

Jim Frame

Active Member
The last antenna change was in 2011, so I don't think that's an issue. (Login credentials to view the CRTN site logs are "anonymous" and your email address.)
 

Shawn Billings

Shawn Billings
5PLS
I mixed up which was old and which was new in your screen shots.

The latitude and longitude in the spreadsheet are also a perfect match with your old screen shot.

Is there someone you can call to ask about the current coordinate broadcast coordinate for UCD1?
 

Jim Frame

Active Member
I emailed Yehuda Bock already, I was just checking on this end to make sure that the receiver isn't doing something I'm not aware of.
 

Jim Frame

Active Member
I just got Yehuda's response:

Jim,
I checked the UCD1 coordinates and they are okay according to 2017.50 NAD83. I also checked the ITRF coordinates - the height doesn't match the one you are seeing either. Please check at your end.
Cheers,
--Yehuda
Is there a receiver setting somewhere that might be introducing the shift I'm seeing?
 

Danb

New Member
Hi Jim,

We have had similar problems in Australia. Have you updated the Triumph-LS software recently?

We're using Triumph-1's with Javad android app. Since an app update in March 2018 all our MGA94 grid positions and heights interpolated from the geoid model have been incorrect. The positions shown in the Javad app are now ~1.4m out, which is inline with the continental drift here in Australia. Unfortunately it was a few months before we realised, and a lot of jobs had to be transformed onto correct MGA94 coordinates and re-issued to clients and government!

MGA94 coordinates should be fixed at Jan 1 1994 position, but the app seems to calculate at the current date, which is incorrect. It hasn't been resolved, so unfortunately we've had to go back to other software, and now miss out on all the extra functions that you get in the app.

Dan
 

Jim Frame

Active Member
Today I shot the same point using UCD1 as the mountpoint, then P268 as the mountpoint. P268 is a lot farther away (9 miles, versus 2 miles for UCD1) and both mountpoints are GPS-only, so I didn't expect the points to agree very closely, but I wasn't expecting this kind of disagreement: 0.48' N, 0.90' E, 0.63' elevation. The reported position for P268 is at odds with its published position in all 3 dimensions, and the discrepancies don't match the ones for UCD1.

I'm scratching my head on this, and would be grateful is someone with a CRTN account can see if they're experiencing anything similar, or give me a clue as to what setting in my receiver might have produced this mess.

Thanks!

UCD1.png


P268.png
 
Top