Network GPS

Sounds like a bad fix, could happen with any type of GNSS, more likely to occur with real time of any type, single baseline, network, your own base station.

SHG

Hi Gavin. Didn't know you were on here, but I was going to get ahold of you on Monday regardless. I'll plot out the points, as was first located and as shot the second time. I'll send you the raw files as well. This type of random error happened again on friday when we shot some control which we then shot between with a total station and it was 13 feet different. We observed those for probably 2 mins each. My crew chief is fairly experienced with GPS and looking at pdop, but it's a new topcon gr-5 on the WSRN w/ the newest survey pro so we aren't used to it yet.

What was your HRMS and VRMS?

My personal experience is that any reading over .30' for those are suspect.

I have experienced what you are saying, but only with high error readings. (Which I define as anything over 0.30'.) Typically I would want much better fixes than that, but if the error readings exceed that limit, I assume the receiver is just guessing.

Thanks for the reminder...

...that RTK, with or without a network, still requires checks and our attention.

Thanks for the reminder...

Agreed on the checks. Out of all the shots, though, these few shots got us. However the field walk afterward took care of that.

The horiz/vert stated were all very tight. Worked with the network folks on it yesterday in the field and the office--boils down to a random error of sorts. Their end shows that during the time of the shots in question it showed a single point position and/or autonomous. However, going back in to the raw data on the Survey Pro 5.2 it showed a fix. It's enough to drive a surveyor to drinkin'! 50 feet is crazy talk.

Thanks for the reminder...

"Their end shows that during the time of the shots in question it showed a single point position and/or autonomous. However, going back in to the raw data on the Survey Pro 5.2 it showed a fix.

that is scary.

Thanks for the reminder...

> Agreed on the checks. Out of all the shots, though, these few shots got us. However the field walk afterward took care of that.
>
> The horiz/vert stated were all very tight. Worked with the network folks on it yesterday in the field and the office--boils down to a random error of sorts. Their end shows that during the time of the shots in question it showed a single point position and/or autonomous. However, going back in to the raw data on the Survey Pro 5.2 it showed a fix. It's enough to drive a surveyor to drinkin'! 50 feet is crazy talk.

IF I can't take a shot on a known point to check an initialization (which scares me all by itself), I will generally break lock, and even do a new connection to the network, and store another shot.

A new solution, with a new VRS solution, that closely matches my previous shots; this makes me feel better.

If you find that it is something in how you were using the network, I would be very interested in knowing that.

Thanks for the reminder...

> Their end shows that during the time of the shots in question it showed a single point position and/or autonomous. However, going back in to the raw data on the Survey Pro 5.2 it showed a fix. It's enough to drive a surveyor to drinkin'! 50 feet is crazy talk.

I have experienced a "false fix" before with Carlson SurvCE, with the network, with the HRMS and VRMS all looking good. It kind of seems to freeze when this happens. Does your raw data display the latency at the time?

Thanks for the reminder...

To me 50' is better than 2' seems easier to catch.

This doesn't really cause me too much consternation, I mean I have created big errors with my total station. What makes us professionals isn't the fancy toys, but our ability to know when the toys aren't giving us the right answers.

Mainly, this serves to remind me not to be complacent in my field procedures, and to make sure all the crews are following those procedures.