GPSMAP 67 RINEX data

[Richard1982]

Richard's RINEX data sample of Garmin GPSMAP 67 (software version 6.60) looks quite promising.

I just wondered... it is possible to use RINEX data to get more accurate co-ordinates of where the GPS was placed? Either through better processing of the signal, or some kind of time averaged position? I was saving the rock as a waypoint and then accidentally saved it twice and noticed that it gave slightly different coordinates (I guess GPS inaccuracy). Not that it matters, I was just curious.

Carrier-phase ambiguity fixing could not be demonstrated with this data set. Maybe the data set was just too short or other problems exist.

I could put it on my window sill and leave it running all night if you like

[LWa]

I just wondered... it is possible to use RINEX data to get more accurate co-ordinates ...

The RINEX files contain the original observations (code and carrier-phase measurements). Combining them with additional data can give much more accurate coordinates. Such data are either similar observations from reference stations, in your area freely available from the Ordnance Survey, or high accurate orbits and satellite clock corrections.

Garmins GPSMAPs produce coordinate results with an accuracy level of a few meters, under ideal conditions. Time averaging can improve this, but you would still be at the 1 m level. With the GPSMAP 66sr it was demonstrated that centimeter level can be achieved in post-processing based on its RINEX data and additional data. The question right now is whether the observations of GPSMAP 67 also have all the characteristics required for centimeter accuracy.

I could put it on my window sill and leave it running all night if you like

To obtain good quality observations, the GPSMAP antenna must be pointed strictly upwards. There must also be no reflective surfaces above the antenna horizon (no walls, windows etc). So a set-up on a window sill is straightforward, but not the best choice for good quality observations.

[SunnyAndShare]

RINEX on a GPSMAP 67 sucks. Based on comments in this thread, it appears that Garmin doesn't care.

I have seven consumer-grade devices capable of outputting RINEX data: Four Google Pixel phones (two 6s, a 7, and an 8), a GPSMAP 66sr, a Montana 700i, and a GPSMAP 67. I use open-source program RTKLIB for post processing. With an open sky, the Pixel phones and 66sr usually put 50% of the observations falling within 60mm (2.4") of the average. The Montana is not as good as 50% of the observations usually fall within 110mm (4.5") of the median. OTOH, the GPSMAP 67 sucks. I'm lucky if the readings fall within two meters of the average. The plot of the 67's GPX data is better than the RINEX plot.

Pixel phones are my go-to device for RINEX output.

[mareksbl]

Any news about Rinex after update to 8.80?

[SunnyAndShare]

Still terrible with 8.80

[Wombo]

With the GPSMAP 66sr it was demonstrated that centimeter level can be achieved in post-processing based on its RINEX data and additional data. The question right now is whether the observations of GPSMAP 67 also have all the characteristics required for centimeter accuracy.

To temper expectations, you are not realistically going to achieve cm with a Garmin handheld.

The 66sr test was an extreme example conducted by knowledgeable experts. For example, it required a special rotational mount and 16 hours to first determine the antenna PCO & PCV's, and setting up an immediately adjacent base to eliminate atmospheric effects, and the results only started approaching cm after 10 hours observation.

With some knowledge and experience you may achieve decimeter on static points, otherwise a reasonable expectancy is sub-meter.

[SeeNoEvil]

First, let me note that I am NOT an expert in the same way as those responsible for the paper some years ago on achieving (with some difficulty to be sure) centimetre level accuracy from post-processing RINEX files from a Garmin GPSMAP 66sr.

However, today (2026!) I did manage to achieve those same kind of results from the same model receiver. Basically I purchased a used unit a few days ago more or less because I was very eager to try this out (even if "just for fun")! This was initially from logging for about 140 minutes in a very open spot.

I'd like to know how well RINEX logging is being handled with the 67 now? Anybody will to share a sample file? I did look at a used 67 also but the price was a lot higher (it was not far from new really) and from what I read on these forums and elsewhere it wasn't really clear if the earlier problems had been ironed out. And the H1 sounded even worse.

Like the authors of that earlier paper, I have found my 66sr seemingly keen to avoid using (logging) Galileo satellites which is a shame from my point of view given they all have support for the L5 (or equivalent) frequency but it is still a bit hit and miss on GPS satellites. There is very little the end user can really do to influence what gets logged except perhaps using the various planning software available to try to choose times when the mix is "good". Within the unit you can choose to use GPS *only* or otherwise everything it supports (doesn't include BeiDou) but nothing finer. (And you can turn multi-band off.) I suppose all this is because the chip inside is trying to minimise power usage and perhaps logging multi-band is more expensive in terms of power. Ditto for why it only uses/logs some satellites rather than all that it can theoretically "see".

Anyway, it can done if you have a bit of patience, etc.!

[Wojtas81]

I have found my 66sr seemingly keen to avoid using (logging) Galileo satellites which is a shame from my point of view given they all have support for the L5 (or equivalent) frequency but it is still a bit hit and miss on GPS satellites.

It is not topic about 66sr, but I am confident that it does use galileo satellites with no issues.
At least mine. Firmware version v6.10, Hardware version: V4, CPE up-to-date.

[SeeNoEvil]

I have found my 66sr seemingly keen to avoid using (logging) Galileo satellites which is a shame from my point of view given they all have support for the L5 (or equivalent) frequency but it is still a bit hit and miss on GPS satellites.

It is not topic about 66sr, but I am confident that it does use galileo satellites with no issues.
At least mine. Firmware version v6.10, Hardware version: V4, CPE up-to-date.

Thanks for your reply and as a result I did find my unit had no CPE.BIN file. It does now! But even before I corrected that issue I did some further RINEX logging and this time it had a decent number of Galileo satellites included.

I have only had the unit for a few days. Maybe it was slowly building up its almanac or similar and it has taken until today to get Galileo done even though I've used it for quite a few hours. Perhaps something else. Who knows?!

Anyway, all seems okay now. Sorry for not mentioning the 67 until now.

Thanks again.