"Gary E. Miller" <[email protected]> writes: > On Wed, 21 Jan 2026 15:31:28 +0100 > Hans Mayer <[email protected]> wrote:
>> and it is about 40.09 km away. > > Ugh. That will not work. I find more them 2km and the benefits are > small. (I'm amused by about including the 90 meters!) It's really hard to say. You have much worse experience with RTK than I do. While 40 km is a bit much, I have great positioning results with network RTK where the closest stations is 20 km, a friend getting sub-cm repeatable positions with a tripod, and me within a 4 cm diamater circle handheld prism pole watching the level. I don't think it is at all clear that the RTCM stream accessed over NTRIP is "bad". Most importantly, this is almost certainly not about gpsd. I would encourage Hans: Log the NMEA from the receiver, or gpsd'd processed version, for a decent interval (min 4h) in autonomous mode, and then again with RTK. Graph each of them to understand how tight positions are. Look at fixmode and see if you are in float or fix. If it's not RTK FIX, make sure your antenna has an unobstructed sky view. You really should be getting positions such that most of them fit in a 10 cm diameter circle. Even if RTK FLOAT, it's likely good to about a meter, which in time should be good to about 3ns (or 6, if one uses the t/h similar and h is 2x as bad as lat/lon). Be skeptical about how the F9P produces PPS. It is an RTK positioning receiver, not a timing receiver. I have no idea what it does with the PPS signal in RTK mode. Read the F9P docs about PPS in RTK mode. Ask u-blox. As a detour, understand the math behind RTK. That's not really on topic on this list, but it's not easy. If you really want to understand, get a stable 1 pps source, like a budget GPSDO (e.g. Bodnar), and a way to compare that pps signal to the F9P's, probably like the TAPR TICC https://tapr.org/product/tapr-ticc/ Or maybe you can use two serial ports and write some code. You could compare an F9P in autonomous to an F9P in autonomous for 4h that goes into RTK for 4h and then back for 4h. Realize that you can either just accept what is, or you can do down the path to becoming a time nut. Complaining to Gary that your results while using gpsd are not what you want, when they aren't about gpsd, is not going to make either of you happy! I think it's a really interesting question what's going on. But it's going to take measurements to figure that out.
