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Post Processing


kc2ixe
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OK - I KNOW I'm going crazy now. I've just run across a program called GRINGO - which allows you to record the phase, pseudorange etc data from 12 channel Garmin handhelds (yes, you are still only single frequency, but...) and outupt Rinex files

 

How crazy would I be to actually go through the bother of recording at an adjusted horizontal point, while going out and recording the scaled horizontal points (Benchmarks), doing the post processing, and reporting THAT to the NGS?

 

aka - am I nuts to even think about this?

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I'd like to see some test results. Find a first order station and go set up the receiver on it and process 15 minutes of observations and see how close the results are to the known values. It's interesting they have no test results up on their page.

As for what they foun for accuracy

 

http://www.fig.net/nottingham/proc/gs_05_cosser_etal.pdf

 

http://www.fig.net/pub/morocco/proceedings...1_schwieger.pdf

 

They seem to be in the 10cm range

 

And I'm NOT going to run out right now, as I would need to buy a 2nd GPSr to take the realtimes at the reference mark, unless there was a CORS station and data nearby for me to get RINEX data from

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I'd like to see some test results.  Find a first order station and go set up the receiver on it and process 15 minutes of observations and see how close the results are to the known values.  It's interesting they have no test results up on their page.

That is what I wanted to know also so I went working on it. And I made many tests.

You can read all about in here: http://www.xs4all.nl/~atarist/geo/gps_accuracy.htm

To summerize: after long observation times ( >1 hour) I managed to get to a few dm accuracy.

And thanks for the 2 pdf-links. They were not know to me.

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OK - I KNOW I'm going crazy now. I've just run across a program called GRINGO - which allows you to record the phase, pseudorange etc data from 12 channel Garmin handhelds (yes, you are still only single frequency, but...) and outupt Rinex files

 

How crazy would I be to actually go through the bother of recording at an adjusted horizontal point, while going out and recording the scaled horizontal points (Benchmarks), doing the post processing, and reporting THAT to the NGS?

 

aka - am I nuts to even think about this?

Just remember that NGS will NEVER use coordinates that are submitted to us for anything other than helping people find the mark. If you want to give people hyperaccurate "to reach" information, I supposed it could potentially be helpful. But my opinion is that everyone would be better served if you spent less time at each mark, and more time looking for more of them.

 

Of course if doing the whole processing thing is fun for you.... go for it.

 

:laughing:

 

-Casey-

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Just remember that NGS will NEVER use coordinates that are submitted to us for anything other than helping people find the mark. ...snip...

I was thinking more for the new HD_HELD1 datasheet type - aka "scaled" marks that are now located with a hand held - I figure the more accurate, the better

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Casey wrote:

If you want to give people hyperaccurate "to reach" information, I supposed it could potentially be helpful. But my opinion is that everyone would be better served if you spent less time at each mark, and more time looking for more of them.

 

Of course if doing the whole processing thing is fun for you.... go for it.

 

Casey:

 

You have to understand that we grew up watching Tim the Tool Man (played by Tim Allen) "turbocharge" everything from autos to porta-potties! We will settle for nothing less than figuring out how to get a consumer-grade GPS receiver to carry SECONDS to six decimals! :P

 

Keep tweaking, Boys! ARRRR, ARRRR......

 

-Paul-

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This is intrigueing. If you do figure out how to do post-processing on handhelds, keep us updated.

 

For the average user, the easiest improvement in accuracy will come from averaging of readings on multiple visits to the mark hours or days apart. This will usually assure that the errors are not correlated because you have a different satellite constellation and ionospheric conditions. It may be less effective for cases where there is a very well defined reflection (metal building) that is messing up the readings.

 

Take a short average each time you visit the mark and note the indicated accuracy (which Garmin doesn't seem to store for you). Form a weighted average of your readings or simply throw out any that have indicated accuracy much worse than the others and do a simple average.

 

I like to do this in DD.DDDDD format because it reduces the quantization in the handheld's read out, but the method also helps with the other formats.

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In a related note...I found this on the NGS site, hidden in plain view on the front page! It's an interesting result. Several consumer grade devices can use RTK signals if only you have a way to receive them and get them in the device. With data capable cell phones becoming cheaper, there's a real possibility for hunters like us to use this technology in states like ohio if we aren't priced out of it....

 

Ohio State Wide RTK Network

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