We have a set of R8 model 2 GNSS receivers and an older set of R8 model 1 GPS only receivers. It has been my observation as of late that the GPS only receivers seem to not work as well near trees, or as often as the GNSS pair (as one would expect), but when they do work (about 85% of the time compared to the GNSS) they seem to yield higher precision/accuracy coordinates.
I have performed a sort of fast and loose experiment over the past month of redundant averaging of the control points. These points are in a wide open meadow, so multi-path isn't a concern, and the bubble has been checked in both rods (fixed hieght).
The GNSS observations seem to average within an ellipse of around 0.10' both horizontally and vertically. While the GPS observations are consistently 0.03' horizontally and vertically.
Has anyone else noticed this?
p.s.: By averaging I mean in an Excel spreadsheet. The TSC2 will average points for you, but it isn't always a "safe" option. If you have observed and averaged any points multiple times in the TSC2, the points will not "update" based on the change of the control points because they are in the DC file as hand entered.
I have always found that. With Navstar alone, you're not mixing two types of sats that, by definition and according to Dave Doyle, there is no direct correlation between. So, while my GNSS receivers seem to lock faster, they get checked more.
Anyway, if it's got to be right, it gets an infill shot on it anyway.
What's really cool is when I use my 5700 base and my 5700 rover and my two R8's as rovers and make infill shots at the same time. Man, that will tighten up some values in a hurry, and you can cover a lot of ground at the time time since you've got three RTK rovers running at once.
I've only done this a few times, but it's nothing to cover 600 to 700 acres in a day.
Yes we had the same problem when we first got our R8's. It was a very noticable problem and we quit using it in GNSS format and complained to our rep with Trimble. Sorry I don't remember for sure but they sent a fix and I think it was firmware for the rover. That did fix it. If you get all the newest updates I think you will find the problem goes away. We were seeing 0.15' when checking in. Turn off GNSS and check in 0.02'. And it was consistent.
Actually the averaged points in Survey Controller and TGO/TBC do not update when you recompute because they are "grid" points....
And no longer have a vector associated with them.
In the office software you can disable the "grid" value and then the individual shots to that point will update.
Tom
I wasn't referring to only GPS projects.
You can be working in a scale factor 1.0 job and at any time, say you change the elevation of your starting point, all points will translate to the correct elevation. Assuming, that is, that no shots are stored as averaged shots. The best way around this is to tell the DC to store another instead of telling it to average, but there are times when you want the shot to be averaged (e.g. moving ahead when performing tight stakeout).
We have GR-3 w/ GNSS. After about 2 mins and no lock using GNSS, I disable all sats above 32 and bingo I have lock. Maybe receiver firmware I don't know but with all the gps sats now I don't think you really need GNSS. Some of those older Trimble receivers work great w/o GNSS. I still use one.
