@ Jon Payne
That's some fascinating stuff. Thanks for deciphering the data.
@ WA-ID Surveyor
Unfortunately, we're going to have to live with those 2 unbalanced legs. Had to get around a 90° curve.
Contrary to that, 2 and 5 are intervisible. We could traverse 1,2,5,7,8. We could push 1 to the south to balance 1,2 with 2,5. We could also push 8 to the north to balance 5,7 with 7,8. What do you think?
I set up the traverse keeping topo shots under 300' to minimize vertical errors in mind. I suppose we could locate 3,4,6 from the traverse. What do you think?
We use L-Net (Lengemann Corporation) for our network solution. We do not have our own base station. We select a single base solution.
I know nothing about fast static. Is that the same thing as PPK?
@ Norman_Oklahoma
I don’t know if we could select a closer base. I could switch to a multi-base solution.
@ RobertUSA
Thanks for your help.
@ dwoolley
Is the “always have a long backsight” an old wive’s tale? Not exactly. It matters if you are setting points or collecting coordinates. A 0.01′ sighting error in 100′ is 0.10′ in a 1000′ in setting points. Network surveying is not staking or collecting coordinates. It is taking measurements. Collecting measurements is not line length dependent – you will be sighting each point, therefore the order is immaterial. If you are a coordinate collector, what are we talking about here? It quickly turns to nonsense.
This is great stuff. Thanks for your help.
If you are measuring angles it makes no difference whether you sight short or long first. The largest uncertainty will be in the short sight whether it is first or last. Makes no difference.
dwooley I'm unsure of the point you are trying to make. To me it seems it does not matter how you express your measurements.The measurements and the error in the measurements remain the same whether you express them by "setting points" or creating coordinate values. The error exists regardless of how the measurements are used.
"I know nothing about fast static. Is that the same thing as PPK?"
Fast static (aka rapid static) is simply static with short baselines - typically limited to 20 km. With short baselines the assumption is that the upper atmosphere is the same at each receiver, therefore there is no need to occupy for a long time (long time being an hour to several hours) to model the upper atmosphere. This 20 km limit is the same limit that there is on RTK'd vectors for the same basic reason.
With fast static you can get a good solution with only a few minutes observation time, but you are limited to short-ish baselines. Plus, you need software to post-process such baselines and do something with them.
We always tried to jump the short backsights, that will tighten up the traverse. Haven't done more than a three leg traverse in 30 years, but when we did do something like that it was always best to jump it, if possible, usually it was possible.
"dwooley I’m unsure of the point you are trying to make."
I think you are reading a bit too much into DWs comment. I took it as simply meaning that when staking out you want the backsight you are zeroing on to be as long or longer than the foresights you are staking out. But when control traversing a series of angles there will be error in the angles, which is related to the length of the sights, but which is the backsight and which the foresight is irrelevant.
<div>A couple of "ifs"</div>
If your GNSS unit is able to collect data for static observations and
If the network you are using also collects the data for its users to have available (quick look at their website seems to indicate they do)
then
You could get a static solution on the two point pairs at each end. This might require a software investment as it seems you might not have the software to post process.
The Kentucky CORS system collects the data and it is available for download to post process in conjunction with your own units. It is very handy to be able to download the surrounding network station data for post processing as they are not all in the national CORS database. I've got some Kentucky ones nearby, but the national ones are much further away. So I can get a good static solution from the nearby stations with a shorter observation time.
The traverse was completed yesterday. The closing azimuth was 6" less than the record azimuth. The traverse length was 3338'. The error of closure was 0.217', giving me a precision before any adjustment of 1:15382.
I will add 1" to each turned angle then recalculate traverse points 3-8 (C101-C108, C for conventional). I have a question about how to do a compass rule adjustment for my closed link traverse. Holding traverse points 1 and 2 (GPS101 and GPS102, GPS for RTK), do I only adjust traverse points 3-8 (C103-C108)?
The scaling of state plane coordinates varies dependent on your relative position on the grid but will will typically be on the order of 0.1'/1000 feet. You have a misclosure on the order of 0.3' in a bit over 3000 feet. Do you see the pattern here? Comparing SP grid coordinates to ground measurements this may account for the greater part of your misclosure. If you have not already done so by some means determine the appropriate Combined Scale Factor and use it to scale your measured ground distances. Then recalculate your traverse.
@ Norman_Oklahoma
Comparing SP grid coordinates to ground measurements this may account for the greater part of your misclosure.
GPS102-GPS101 Grid distance: 629.431'
GPS102-GPS101 Ground distance: 629.515'
GPS107-GPS108 Grid distance: 677.985'
GPS107-GPS108 Ground distance: 677.981'
If you have not already done so by some means determine the appropriate Combined Scale Factor and use it to scale your measured ground distances.
I don't know anything about this, but I'm learning. Isn't the grid scale factor calculated by my field software when I create a new job?
Please see the attached file if you want to review my traverse.
This is should help. This is not exact but should be close enough for a math exercise. Take your state plane starting coords. And all your sudo state plane coords along the route. Go to NGS website for NCAT. Plug them in appropriately units datum and zone. You can do one at a time at the bottom you can get the CF combine factor for each one. Your starting pair and ending pair are true the ones along the route are not exact but the CF will not change that much. Write all those down. Take your raw run between all points as is convert or inverse those pairs get the bearing and distance. Draw it on on paper. Make sure they are running in the forward direction. Set up a table the first pair is known that distance inverses assume is correct grid distance. From your first occupy to the first fore sight you have a ground distance. Take the cf of occupy and cf of fs. Add and divide by 2 that’s the avg cf of that line. Now show ground distance use the cf to convert the ground to grid distance. Hold your bearing do this throughout. After all ground distance are converted to grid. Cf * ground dist = grid. Plug those into your table. Two pairs are already grid distance starting and ending pair I assume. Now it’s just a triangle. Right triangle. Take the sine and cosine of the bearing convert to decides first. Multiply that x’s the grid dist this will give you a delta north and east. Watch your signs neg and positive. Keep those in your table. Once all through. Take your angular error. And the knew deltas north and east we call these latitude and departure simple arithmetic now to get those deltas to your starting coords. And see how they end up on ending coords. The angular error is also in need of adjustment. That’s a quick not exact compass rule. There are some rules to follow like in theory doing a compass rule I usually start with the most westwardly point. This is not exact. I just can’t type every step on the phone lol. But that should get you heading in the general right direction.
This is more of a combination of grid traverse and adjustment together. This assumes that all c/r differences in height of target and instrument have already been accounted for. So we are just adjusting the sudo ground coords along the route. To grid. Then reapplying the angular error aka bearing misclosure to readjust . I would honestly have to sit down and look at everything to have all the steps. This is just in my head.
