Hello, I am new to this site and do believe communication between surveyors can be a productive thing. So let me get involved by asking some questions about GPS which I have never used personally but have had crews that use it.
1. In basic surveying a traverse loop is necessary and should have a good closure or be adjusted. With GPS how do you check and know that those coordinates are accurate?
2. If accuracy is a great necessity would you choose a EDM over GPS?
This Content Originally Published by a land surveyor to Land Surveyors United Network
There are a number of ways to improve your certainty on GPS. A simple method that I use most of the time is I set up my base at a know location. Then with my rover I shoot control points in RTK. I will then move my base to a new location and shoot my control a second time. Then I move my base to a third location and shoot control a third time. I will then mean the coordinates. If elevations are critical I will run a level loop through my control. There are other techniques I use depending on the project (static, PPK, or a network of OPUS solutions), but what I described above is what I do 60%-70% of the time.
1. Train with your tools until you have absolute confidence in how they work. Then remember the three words that guarantee accuracy with any measurement. Redundancy. Redundancy. Redundancy.
2. The choice of tools depends on the work environment. In a place where GPS works well GPS is the right choice. In a place where the EDM works best use the EDM.
1. Utilise independent vectors (RTK or post processed - like a double polar in conventional survey).
2. Be very aware of the "calibration" that the GNSS system is utilising.
3. For more accurate GNSS levels apply the relevant geoid
4. For precision setting-out work (<15mm) use a total station with atmospheric, sea level and projection corrections applied where applicable
Don't trust only one tool.
RTK GPS is essentially a side-shot or radial technique. Multiple occupations help redundancy.
A GPS control network is adjustable and likely more precise.
A traditional traverse would be improved with cross ties, something the GPS network includes.
No matter what you use to measure, surveying is about seeing and gathering evidence.
One must look and analyze ALL available data to make a decision, unless one is simply doing (so-called) engineering surveying (layout).