We need to do a boundary Survey, Level & Feature survey under a area of high voltage power lines. There are 4 high voltage power lines running parallel in the corridor. We need to do the survey under it . Approximate width & length of the area is 150m*500m. Need to take levels in 10m intervals. We have a SP80 receiver & proposed method is network RTK. We also have Total Stations. Can anybody give me suggestions to take Network RTK measurements in this situation please?
Thanks & Regards,
Nimal
-Assuming acceptable conditions, use RTK to lay out your 10x10 meter grid. I would use a spike or some sort of semi-permanent mark you can occupy with the total station if necessary. Plan this with georeferenced orthoimagery before you even get to the field.
-If RTK heights are accurate enough and acceptable, just run with that. If not, use a level to assign elevations to your grid points.
-Traverse through your grid points (where convenient) for your boundary determination
-Use a reflectorless total station with a right angle eyepiece to locate the lines if required. Note temperature, time, weather conditions, ect, ect.
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That would get me headed in the right direction...your mileage may vary.
It all depends on the accuracy of network RTK in the?ÿ?ÿarea of your survey, what tolerances are allowable, what the topo survey is for.?ÿ As previously mentioned?ÿ you could layout the 10m by 10m grid with RTK, or if very slight tolerances are allowed, layout outer control with RTK, and do everything else with total stations and levels.
Thanks very much for the quick responses. I think the Network RTK should work really well. Because the CORS Base is just 5km away. Our main concern is the possible interference with high voltage power lines.?ÿ
The area to be developed as a parking area. We also need to measure the ground clearance from the sagged powerlines.
?ÿI would set two control points with the GPS, then do the grid under the High Voltage power lines with the total station, with 2 or more set ups to keep the vertical accuracy, besides you need to break out the total station to get the height of the wires, why not use it for the grid and not have to worry about?ÿinterference.?ÿ
I don't consider myself a GPS expert, so don't know if there are recent models on the market, or your model in particular has included technology to be able to effectively filter out the distorting effects of overhead high voltage.?ÿ Because of the possibility of interference, I would be very wary of using RTK too close to the corridor with the electric lines but would use it to bring in control just outside of the perimeter if that was the most efficient way to do it.
Whenever a grid is specified, my first concern is "what if high/low points or grade breaks occur between grid points?"
I think the best way to do the topo part of the job is to shoot it with your TS as normal, hitting high and low points, following grade breaks to define breaklines, and picking up other features as required, then to fill in with random ground shots so that your overall spacing is at least as extensive as the rough equivalent of the required grid spacing.?ÿ Process the data into a surface model as usual and from that, generate a grid to satisfy the engineer who wrote the specs.
If they want to see the grid staked out on the ground, explain to them the advantages in accurate mapping for you to do it as described above and that if they really need to see the grid staked on the ground, you can do that, but for mapping accuracy you will likely need to take at least as many shots off grid points and that by staking the grid, they are adding cost to the job without adding accuracy.?ÿ If they just want to see a stake farm but there is no other practical use to the grid, they will allow you to do the job more efficiently.?ÿ
If they are the type of engineer who feels that they know your job better than you do, then they will attempt to overrule you or go with a lower bidder who will shoot just enough random points to make a reasonably accurate set of contours, slam in the grid stakes with RTK, not caring about the probable effects of the OH wires, and produce a map with ugly and unlikely contours.?ÿ In a case like this, you can remind them that they are the experts regarding the design they will be making predicated on the survey data and should have the best idea of the level of precision required for their base data, but you are the expert at determining the best and most cost efficient method to achieve accurate results at that level of precision.?ÿ If they insist on dictating method, then it will cost them either in terms of cost, accuracy, or both.?ÿ Their choice.
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I have worked under high voltage lines and inside sub stations with RTK and Total Station
?ÿBe sure to use carbon fiber, not aluminum poles or legs.?ÿ
I have not had interference issues with RTK rover. Never put your base under?ÿ a high voltage line. I have gotten static shock in the eye ball looking through a Total station on a damp morning with fog when power lines are buzzing. Not much fun, I suggest you avoid working durring wet conditions or use RTK. In most sites we need an escort and safety training by the utility companies. They tell us to stay at least 10ft away from everything and never carry the pole over your shoulder. If you hear a pop, stop don't pickup your feet. You must shuffle out, to stay grounded.
That's been my experience.
