Freaky OPUS Stuff....Why?
Posted By Trimble Man on 2/1/2002 at 7:31 PM


As part of our little science project working on the Blue Board..I've been doing several overnight OPUS sessions to determine positions on two points...
These points are only 18' feet apart..
As a mistake I sent the same OPUS file that had already been sent, but recei
ved different results..

The first time it used PRCO,ARL5 and HKLO...
The second time it used PRCO,HKLO and JTNT...

Same file, same time span, same IGS Ultra-Rapid orbit...

First Report produced;
N 454304.4654
E 1835106.3167
Ellips 1031.0970
Elev 1115.1979

Second Report produced;
N 454304.4785
E 1835106.3101
Ellips 1031.0609
Elev 1115.1618


So we have;
N 0.01
E 0.00
El 0.03
Ellips .03


Very minor and not at all worrying , but why the two different solutions to the same file at the same time...Actually a good thing in my thinking...A complete different solution to the same station...

But why did OPUS do it different?

TM



Re: Freaky OPUS Stuff....Why?
Posted By jerry wahl on 2/1/2002 at 7:38 PM

Just a WAG, CORS data for some station(s) weren't available yet the first time you submitted it.

- jlw


A little more info...
Posted By Trimble Man on 2/1/2002 at 8:09 PM

First session reported 99% Obs used with Fixed AMB at 90%
RMS 0.021 (m)

Second session reported 98% Obs used with Fixed AMB at 93%
RMS 0.021 (m)..

Your probably right Jerry, since the first time I sent the data was in near real time, while the second was almost 12 hours later..

Still interesting on how close they compared..

TM
Modified By Trimble Man on 2/1/2002 at 8:10 PM

OPUS options
Posted By Phil athome on 2/4/2002 at 10:56 PM

As I recall the OPUS docs say it will use the three nearest CORS. My guess is that means the three nearest for which it has data.

I submitted the same file on the day after and then again two weeks later to see the difference made by the precise ephemeris. On the second go round one of the CORS was replaced by one closer to my location.

So I still don't know. Was the difference the precise ephemeris or the different CORS used to compute the results? Either way, I liked the numbers pretty well.



We figured it out Phil...
Posted By Trimble Man on 2/5/2002 at 6:13 PM

I sent the first file the same day, and Kent informed me that the Texas CORS only upload daily files..So the next morning then this data was available.
I agree...Two different solutions, and both very acceptable with different stations....

Deral