I was using RTK on WSRN today to create a base line to start a job. My precision was down to 0.03 after about 2 minutes on both points. I set up on it and backsighted and my residuals were about 0.6' both vertical and horizontal. I made sure I was plumb and was using the correct glass, etc.
I then noticed that there were high Ionospheric condition this morning in the NWWA region. Even though I was not directly in that region and surveying at the time of the high ionospheric conditions were present I feel that this was why I was getting this result.
My main question is when there are solar storms, or bad ionospheric conditions, does your GPS residuals still read as being good or will they actually give you bad readings or not be able to connect at all, so that you would know right away.
Maybe there was something else going on, which is what I am trying to figure out. I set another gps point a little further out and when I set up on it the results weren't as bad but still concerning.
The 'precision' or whatever the quality indicators on an RTK controller display are nearly always overly optimistic. They are just one of the things to watch.
It sounds to me as though you had a bad initialization. Ionospheric conditions and poor environment can both cause it to happen. Repeat observations and re initialization should be part of your work flow to catch when it happens.
A lot depends on your RTK configuration as I understand it. When connecting to a VRS system as we have here in Belgium with a lot of reference stations the VRS system is able to filter out (most) of the errors introduced with the bad ionospheric conditions.
There are other factors. A month ago, I set a nail out in a nice clear area. Came back later (During marginal gps geometry) reshot it, and BOOM! 0.3' off! (Horizontal) What was happening was POOR GPS geometry. The ERRORS I get from RTK come about during periods of BAD Sat Geometry, during transition to GOOD, and During transition from GOOD to BAD.
Transition times are the times it answers you, but it not a very good answer.
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Thank you guys. That all makes sense. I may go to that area just to reshoot and check my results again.
Sebastian, post: 326626, member: 9670 wrote: I was using RTK on WSRN today to create a base line to start a job. My precision was down to 0.03 after about 2 minutes on both points. I set up on it and backsighted and my residuals were about 0.6' both vertical and horizontal. I made sure I was plumb and was using the correct glass, etc.
I then noticed that there were high Ionospheric condition this morning in the NWWA region. Even though I was not directly in that region and surveying at the time of the high ionospheric conditions were present I feel that this was why I was getting this result.My main question is when there are solar storms, or bad ionospheric conditions, does your GPS residuals still read as being good or will they actually give you bad readings or not be able to connect at all, so that you would know right away.
Maybe there was something else going on, which is what I am trying to figure out. I set another gps point a little further out and when I set up on it the results weren't as bad but still concerning.
Yes. It will straight up lie to you during poor conditions. Now, L1 RTK is probably more susceptible to it that L1 and L2, but if it's bad enough, we won't even pull it out. Some months back, it seemed like there was a Class X solar flare every week or so and the residual effects seemed to last for a day or two. I used to check it every day during that time but I've become complacent now so I haven't.
I've seen it so bad where OPUS wouldn't process the data.
Sebastian, post: 326626, member: 9670 wrote: I was using RTK on WSRN today to create a base line to start a job. My precision was down to 0.03 after about 2 minutes on both points. I set up on it and backsighted and my residuals were about 0.6' both vertical and horizontal. I made sure I was plumb and was using the correct glass, etc.
I then noticed that there were high Ionospheric condition this morning in the NWWA region. Even though I was not directly in that region and surveying at the time of the high ionospheric conditions were present I feel that this was why I was getting this result.My main question is when there are solar storms, or bad ionospheric conditions, does your GPS residuals still read as being good or will they actually give you bad readings or not be able to connect at all, so that you would know right away.
Maybe there was something else going on, which is what I am trying to figure out. I set another gps point a little further out and when I set up on it the results weren't as bad but still concerning.
I think RTN's are extrapolating refraction corrections from the CORS, so would be affected by disturbances unless you increase occupation time considerably. For instance, OPUS-RS documentation says you need at least 1 hour occupation for that correction at the CORS and then it extrapolates to predict it at the rover. OPUS-S with 2 hours or more occupation solves for the refraction at both the CORS and the Rover, hence the better results. I have had OPUS reject 1/2 hour sessions when solar storms were active, and return solutions that turn out to be a foot off (but you can tell from the quality indicators that it's not a great solution). With RTN work you don't know unless you check it like you did. I'm sure someone will correct me if wrong, but that's my understanding.
I will definitely change the way I use GPS now with taking more shots rather than 1 long one.
Lot of great info, thanks!!