In processing the unreasonably long vectors in my little experiment, what would be the results of the data quality if the iono correction file is left out. I have always copied the iono file as well as the almanac file (just to always have the latest available) to every project file. Is the iono file used in any way in the actual processing? I know in the past when users were requested to send data files to Tech Support for analysis the request only included the B and E files (and D files for Kinematic).
Just to put it to rest, would the iono file serve any purpose in processing these long base lines?
Thanks
J.D.
p.s. If you guys see anything wrong in my analysis methods or procedures with the software in conjunction with the L1/CORS test, please let me know.
Modified By J.D. Billings on 12/12/2001 at 11:47 PM
Don't let anybody get in your way guys. I have been trying to stay out of your way and lurking here watching what is going on.
You are so far outside the box with this stuff that you are writing the rules in my opinion.
The proof is out there on that POST and in what you can get done with your cooperative project.
I know Deral likes to mess with those ITRF positions and they probably represent a more "accurate" coordinate but my choice would be NAD83(HARN) even if it does get a little sloppy when you cross state boundaries. It is the best way to see if you are matching with local HARN stations that are going to be your best check on the results.
Glad to see you're still out there, but "lurking at home"?
p.s. By the way, your experiences with the long base line results with L1 that you shared with us a few weeks ago was part the inspiration to start this little bit of experimentation.
Thanks
J.D.
Modified By J.D. Billings on 12/13/2001 at 6:54 PM
When you guys started this exercise I figured I may have been the match with my comments about long lines. But the longest line I ever did with L1 only was 52 miles.
You outgrew me rather quickly and I have been lurking in awe and admiration of what you are doing.
you still da man
I'm using Ashtech Solutions 2.5. You weren't. Not a fair comparison.
I'm still hanging in here, waiting to see if anybody thinks those IONO files are used or meaningless...
While not yet an Ashtech guy, allow me to take a stab at your question...
Dual Frequency- Not used, since the software uses double differencing to remove the iono (hence Iono Fixed Solution). This is possible because the Iono affects the L1 and L2 differently. The software can correlate these to calculate the proper correction to apply to each SV..
Single Frequency- Not used, the software uses the broadcast message for the calculated error. The message has eight coefficients for computing the group delay..
Since the dual's measure both wavelengths, then it's not necessary to have an Iono model..It's directly removed in the processing. With Singles then the model is very important and your results will vary with the difference in the 'real' Iono versus the modelled Iono.
I'll go out on a limb and say that the possible use of the Iono file is for researchers to use when looking at the double difference (measured correlation) versus whatever new algorithm they are working on at the time...There is quite a bit of research going on at this point on the Iono (and most is space born measurements)...
TM
PS-Ready to be corrected if someone knows otherwise...
I think you're probably right. I seem to remember Bill Martin may have shed light on this a year or so ago. I couldn't remember exactly what was said, and didn't remember the reason given for the iono file's existence in the directory.
j.d.
From the AS manual:
"iono corrections—GPS satellite ionosphere corrections file. The iono
corrections file is only created by a Locus receiver."
If ever I ask for somebody's data files, I want them all. For whatever purpose it may serve, it's a part of the record of the survey.
Phil,
That being the case ("iono corrections—GPS satellite ionosphere corrections file. The iono corrections file is only created by a Locus receiver.")what is the purpose of the iono file. Can it be accessed for any possible need of the user?
And the big question is what is actually "created" in the file?
I know these are tech questions, but a few of us have been pondering this for quit a while.