RINEX Application

Thanks for wonderful clarification. My head was more foggy, but I reached the same conclusion!

Are you familiar with GFZRNX? They seem to be free to non-routine, science and educational projects. But one has to register to get details, and I haven't.

GFZRNX is a general utility for manipulating RINEX files. For example I use it to convert V3 base files to the V2.11 for my legacy Trimble post processing software, but it won't do anything like post processing itself.

Ok, thanks so much.

I just purchased the GPSMAP 66SR earlier this week specifically because it advertised RINEX data collection capability. I own a ranch and need to build a 3500' fence along a property line that I will need to bulldoze. Although the property line is a straight line in two dimensions, I have gullys and hills that restrict my line of sight between the two points. I had the land surveyed by a professional surveyor, but at a thousand dollars/measurement, I figured getting RINEX measurement performance would be good enough, and the money saved would more than offset the cost of the unit.

My plan was to extract the RINEX measurement from the device and download it into the NOAA On-line Positioning User Service (OPUS - see https://geodesy.noaa.gov/OPUS/about.jsp#FAQ). When I submitted the data I received the following error message:

The internal format of the raw file you submitted to OPUS could
not be converted to RINEX by NGS and is therefore not supported
by OPUS! 

Please convert the raw file to RINEX before uploading or contact
your receiver manufacturer for an alternative solution.

I have requested the same information from Garmin, but they didn't seem to be interested in making the GPSMAP 66sr RINEX output usable in any way.

:(

That's very unfortunate. That's not the kind of insight I was looking for. I have bought several Garmin products in the past including the Zumo and two GPSmap 78SC's, and never had a problem with Garmin supporting those products. If they are going to advertise a measurement capability for their product, I would think they are ethically obliged to support it. Hopefully your experience is an isolated case, and that I didn't buy a 500 dollar brick that I have no use for. Guess I should  make contact with the seller to see what their terms are for sending it back. My 78SC has more than enough accuracy to set up a line for a bulldozer to follow so I don't really need another GPS unless it is going to provide me with the capability that I really need..

Anyone else on this forum have a more positive experience with processing RINEX data? Is there a Garmin representative monitoring this forum that can address this issue?

Thanks

Rinex is a significant step up for Garmin putting a toe across the barrier into the realm of professional, scientific & serious enthusiasts. And the applications for post-processing are highly specialized and typically very expensive. RTKLIB is free but significantly more complex than most. Users in specialized fields would typically have access to their own apps.

To be fair, with the minimal number of Garmin only users using the RINEX it would not make sense for them to attempt their own app. They have stated they don’t support any apps, but you could argue it could have been made clearer in the product specs for purchase decision. https://support.garmin.com/en-US/?faq=7iMJZdoCcM2562XlKlMC76

The file itself should be OK. I can process 66i V3.04 RINEX in Trimble Business Center and also RTKLIB so it’s more likely a shortcoming in OPUS. My 66i is single frequency only so I can’t run it through online processing to check.

GFZRNX can strip out things like constellations & observation types etc. so it would be worthwhile trying to thin the file down to the basics to see it gets through. It’s tricky to set up, but if you figure out what you need you can put that string in a command file in the same folder as your RINEX file and you would simply double click the command file in the future.

Be aware that online processing is static only so the unit would need to be stationary over the spot preferably an hour or more.  And you would need to start/stop RINEX logging in the 66 settings to obtain a dedicated static file for only that spot.

And post-processing is not ideal for staking out a fence line. E.g., if you have mapped out the fence line you want, after post-processing you would have a reference point and would need to return and measure out the offset to the line you actually want.

If you could make available a sample RINEX file from a known point like a survey mark or something that could be clearly seen in Google Earth some of us might be able to look a little deeper?

Sorry for the late response to your reply. Had some other things on my plate that had to get done.

I actually considered building my own station using the u-blox ZED-F9P module, but I really didn't want to go down that rabbit hole if I could buy something commercially available. I've built units like this in the past so I know how much effort it would take, and all I really want to do is build a fence.

It is difficult to speculate on the differences between RINEX formats between OPUS and Garmin. I randomly selected a RINEX 3 file from https://geodesy.noaa.gov/corsdata/beta/rnx/2023/017/tn49/ which I was able to run through OPUS. I modified the header file to make it look more like the Garmin file to see if that created any errors, which it did not. For example, I removed the antenna data, the number of satellites, and the "TIME OF LAT OBS" entry from the header data, and it went through with no errors. The biggest difference was in the data. The tn49 file consists only of dual-frequency data that was solid with no dropouts. I wrote a script that processed the Garmin data to remove all single frequency data, and any data that had dropouts in the message. I still couldn't get the data through OPUS so there is something else that is fundamentally different between the two datasets. The tn49 file includes several integer fields which are not in the Garmin data which I provided in my original message for the G06 satellite. It would be useful if I could find the format of the Garmin data fields that the unit is generating.

I was hoping to avoid wading into this swamp, but here I am up to my knees. I guess I need to look at the other tools that you mentioned including RTKLIB and GFZRNX to see if I can process the Garmin data to enable OPUS processing capability. I have a gut feeling it is close. I collected a Garmin RINEX file next to  surveyed point that I could provide if there is a way to share it. I averaged a waypoint for about five minutes at that location on the 66SR and it measured a location 10.5 feet away from the surveyed point.

Thanks,

WR