Community Forums


tricks for tighter control?  

Page 1 / 2

Posts: 18
5+ posts
Joined: 3 months ago

i am still very green, 2 years surveying. i really like boundary and topo surveys, but lately ive been doing more construction. most of the time i get search points from the office of previous surveyed control points, go to the job, try to find a couple based on desc, scaling...then occupy one and back sight the other, try to angle check another. if it under a tenth, i roll.

however, i am partial to setting up jobs using VRS GNSS. i have GPS+GLONASS subscription so i get a lot of satellites.  and when you can set up and calibrate a job without traversing all day its nice. BUT....everytime i do this, the next time im out on the job to stake something, and i set up the total station, my setup deltas are sometime more than a tenth off which is no good for staking gravity flo pipe, curb, grids....or at the very least it bugs me. i can get  under a hun with a gun setup, but GPS setup jobs are way less accurate. i typically occupy the point for a full 3 min obs. lately i will run back through the points and re observe them and avg the obs together, which seems to help.

any tricks or comments about setting up a job with GPS???



Topic Tags
6 Replies
Posts: 29
20+ posts
Joined: 8 years ago

Have you tried raising your Elevation Mask to reduce the satellites at the edge of the horizon?  I usually set mine to 15-20, it gets rid of the satellites that are "noise" that affect your residuals.  Also, of course, check your rods/tribrachs for plumb and prism constants.

flyin solo
Posts: 1216
1,000+ posts
Joined: 6 years ago

Another consideration is time spread between the shots you average. An hour between shots should give enough time for the satellite constellation to sufficiently change. Otherwise you’re just averaging shots off the same setup, basically. 

Paul in PA
Posts: 5763
5,000+ posts
Joined: 9 years ago

There are no tricks to getting tighter control, you do it right and do not expect anything else to help you skate by.

Paul in PA

Nate The Surveyor
Posts: 8731
5,000+ posts
Joined: 9 years ago

Gps is a statistical measuring tool. Measuring FROM moving objects in space, (satellites) to spots on an earth, that is wobbling, and spinning. The measurement signals, are passing through a liquid/gaseous substance, called earth's atmosphere. Which is not the same, at all locations.

For this discussion, we're going to leave out bad inits. (These are blown gps shots, that are wrong, by 0.5' to 15', typically)

If you take a 3 minute observation, it's giving you "the truth, as best it can, within that pile of data".

If you come back, and re-observe, it will give you the best it can, for that data set. And so forth. You can average several observations. This compiles data, from differing times.

Assuming there is nothing interfering, eash additional observation, statisticaly improves the data. It can really yield tight data, over long distances.

TBC.... To be continued...


Page 1 / 2