We are new users of GPS - have Ashtech Reliance X 3 receivers. A number of projects here involve centreline surveys of existing roads and tracks.
We are attempting to convince clients that these could be undertaken by GPS, possibly attached to a vehicle.
What we need is some examples of similar surveys, showing accuracies, methods and problems.
Also the terrain here is extremely mountainous, and at high elevations.
Your reply is most welcome.

What accuracy level do you need to acheive?

Accuracy required will vary on project and terrain. Say +/- 0.1m as the best, however +/- 0.5m to +/- 1.0m may suffice for certain projects.
What I need is some example projects demonstrating the accuracy obtained.

Guess I don't understand what type of survey you are doing. Alignment/ROW survey won't work from a vehicle but a profile of the centerline could be obtained this way if you are carefull. The alignment would be like a topo of the CL, .5' more or less.

Just trying to help.

Ed

Guess I don't understand what type of survey you are doing. Alignment/ROW survey won't work from a vehicle but a profile of the centerline could be obtained this way if you are carefull. The alignment would be like a topo of the CL, .5' more or less.

Just trying to help.

Ed

Yes, collect GPS coordinates for the road centerline with Reliance equipment mounted in a moving vehicle if this is GIS data capture. You have the option with Reliance to collect Points, Lines, or Polygons (check out the nesting feature also, so you can grab some controls in transit).

If you are new to this, take the equipment out and do some of this work before hiring out. Do the same track several times on several different days and compare the post-processed results. you can get a decent idea of what the amount of error was on those tests. Repeatability is necessary to gain any confidence in the end solution. I would be shocked if you got the exact same solution twice.

We have done this many times with static collection, especially when deciding which brands and models of GPS equipment to use in a specific program. We always include some NGS monuments in our trials so that we have some truth in our tests. We have done some work with lines and polygons (and plan MUCH more) but do not have as much experience with these.

Make sure that YOU are confident of what the receivers are giving you. When you are,,,, you'll be able to pass that confidence to your clients.