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State Plane Coords
Posted by nate-the-surveyor on February 26, 2015 at 2:16 pmData Flow.
I am just knowledgeable enough to get my feet wet, but the baptizing is yet to be.
Here is a survey that the client wants, needs GROUND dimensions. But, you are going to run it all in SPC.
How would you do all that? I politely ask, because I have never done it.
I spoke with a surveyor the other day, who before doing such a project, would go set his base out of 1/2 a day plus, and opus it, then after getting the FINAL base coord, would go and perform the survey. (This was an RTK, and RTK/Static Job)
This way, all his raw data was related to the SAME base coord.
Anyway, what data flow do you use?
I use State Plane Bearings alot.
Thanks!
Nate
DeletedUser replied 9 years, 2 months ago 10 Members · 22 Replies- 22 Replies
Nate,
I would perform all work in SPC. Use Static GPS Static to get it started. Then use EDM with CSF in controller to maintain grid coordinates.
Then draw in SPC within CAD file. Apply the CSF in your Cogo software. Use only the Cogo software for all manual entry and to label the ground distances of all dimension using the CSF.
This will give you grid coordinates and ground distance labels. But if you “measure” in CAD you will get grid distances.
Be certain to show your CSF, noting ground distances shown on the plat.
This is how we perform DOT work. In the past we had to show USfeet and Metric dimension on same ROW map, a real PITA to fit all of that on plat.
Lee Green
> Data Flow.
>
> I am just knowledgeable enough to get my feet wet, but the baptizing is yet to be.
>
> Here is a survey that the client wants, needs GROUND dimensions. But, you are going to run it all in SPC.
>
> How would you do all that? I politely ask, because I have never done it.
>
> I spoke with a surveyor the other day, who before doing such a project, would go set his base out of 1/2 a day plus, and opus it, then after getting the FINAL base coord, would go and perform the survey. (This was an RTK, and RTK/Static Job)
>
> This way, all his raw data was related to the SAME base coord.
>
> Anyway, what data flow do you use?
>
> I use State Plane Bearings alot.
>
> Thanks!
>
> Nateif you do this in opus to start control, find the scale factor in the report. choose a wise, centralized coordinate, and scale your grid coordinates by the inverse of your scale factor, using that centralized coordinate as your origin of scaling. include all of this in your plat metadata (sacle factor, origin of scaling, mapping angle, control stations used and their coordinates, etc.), and you are there.
the bigger the project, the higher the elevations above reference plane, the more important this gets
I have 4 locus units, and know how to pick a combined scale factor… There’s yet lots to learn.
Do you set a scale factor in Carlson Survey, to that it will scale the labeling dimensions?
I’m a GROUND surveyor, and now I know I am a flat earth surveyor!
N
> I have 4 locus units, and know how to pick a combined scale factor… There’s yet lots to learn.
>
> Do you set a scale factor in Carlson Survey, to that it will scale the labeling dimensions?
>
> I’m a GROUND surveyor, and now I know I am a flat earth surveyor!
>
> Nlocus are good receivers.
check your scale factors in both your EDM and your controller. if i remember right, you set your edm for no corrections, and set your controller to appropriate corrections. when in doubt, test on a CBL
Nate, I’m kinda in the same boat as you. Recently stepped into a VRS network receiver. What I have done, is pick one point central to my project. After downloading my SPC’s to my CADD program, I apply a scale factor to get me up to ground. I do all my boundary calcs and calls in ground distance. If I need to go back out with the receiver I just scale my coords back down to grid and upload to data collector.
Dude, map it all in state plane, draw it all in state plane, scale the linework up by the csf, annotate, voila.
Or, you could use the routine in Carlson if you have it, to annotate the distances in surface and maintain the grid coordinates.
Kris,
That was what I was thinking would be the best to work on.
Nate
I did it that way a few times. Then I read on how to make Carlson do it. Then I said screw it, I’m on the grid and I keep it all on the grid. 🙂
> Anyway, what data flow do you use?
Set up your base and do your work. Have the base collect data for OPUS as you work your RTK.Back in the office, I would send in the base data to OPUS, import the raw vector data to StarNet, fix the base end of the vectors to the OPUS position, and reprocess. StarNet will output a scaled to ground (also rotated to a BOB and translated) file if I so wish. I’d probably translate so that the base was 10000,10000 -to avoid confusion. I’m not absolutely certain but I’m pretty sure that a similar operation could be done using SurvNet, included with Carlson Survey. Once you have the translation and shifting set up subsequent days of data in the same coordinate system will have the same shift and scale applied.
Even if you don’t have any means of reprocessing (adjusting) the vector data you could perform these scaling and translating functions on the coordinate file in a spreadsheet such as Excel. And if you don’t have Excel then Open Office’s Calc is a free alternative. Doing it this way at least gives you a paper trail from field to office.
You can, of course, easily shift and scale the coordinates in a CAD drawing file. I suspect how 95% of all such data gets “adjusted”. But that leaves no paper trail, no record of how the data was handled. Or mishandled, as the case may be.
Data flow?
My imagined data flow looks like this:
Go and set up base, one pt set up, and set rotation with theta so it is on SPC bearings, and ground coords.
Do Complete job.
While performing job, store raw GPS at base.
AFTER completing job, SCALE all coords, and text, and everything to SPC for archive.
Now, when doing another job, nearby etc, then I can repeat, and the coord systems have a common denominator. BUT to use it, I have to work with a scale factor.
HMMM I’m working on it.
Anybody got a good book on this?
I realize there are 32 ways to skin this cat.
N
> AFTER completing job, SCALE all coords, and text, and everything to SPC for archive.
If you scale the coordinates they will not be state plane coordinates. State Plane coordinates have scale factors associated with them, but they are not, themselves scaled. They are projected.The single best book on GPS and coordinate systems I know of is Jan van Sickles GPS for Land Surveyors. The 3rd edition is the most recent.
This is bad procedure. I would highly recommend anyone learning State Plane stay away from scaling coordinates. You scale distances, never coordinates. This is just my opinion so please don’t take it as a personal attack, it is not.
Nate your software should allow you to work on the grid and label ground distances by inputting the parameters. Your coordinates will stay at grid. Your DC software will need to be set to reduce ground data to grid in the field for total station data. Alternatively, you could use LDP’s which sound more complicated than they really are. There are other methods too, but those are my recommended workflows.OK, so we take projected coords, and scale them to a combined scale factor, now they are quasi ground coords. Well and good. Then, we take, and make new coords, based on the ground coords we have. Then, we scale the whole mess back to SPC. Don’t we pretty close have SPC now?
N
Thanks for your criticism. I guess books are on my agenda.
for the next few weeks, I have other stuff on my agenda… but I like to think about stuff, and you are helping.
N
Nate, I found a little short read by Richard J. Sincovec with Edward James Surveying of about 21 pages in length. It talks about this very thing and working with grid and ground. It won’t take too long to read it, and I have stored it on my I-pad for re-reading from time to time.
I agree with other posters: work in state plane. Use scale factor to get ground distances. If geodetic directions are required, then have your field software or CAD software translate and rotate. But always preserve the integrity of your state plane coordinates.
> …. Don’t we pretty close have SPC now?
Yes, you would.Thank you Harold.
I’m compiling a little to read list. I think this will be at the top.
I used to hear them talk about projections, at conventions, and get real mad. Local surveyor was still working with compass and tape, and shortcutting, and here I am fussing about NAD 29 and NAD 83 and I wanted to go out and abuse my head on a brick wall!
🙂
N
> Thank you Harold.
>
> I’m compiling a little to read list. I think this will be at the top.
>
> I used to hear them talk about projections, at conventions, and get real mad. Local surveyor was still working with compass and tape, and shortcutting, and here I am fussing about NAD 29 and NAD 83 and I wanted to go out and abuse my head on a brick wall!
>
> 🙂
>
> NI think you mean NAD27 and NAD83,the associated verticals are NGVD29 and NAVD88.I saw the typo in Sinc’s paper also.
State Plane Coordinates were invented in the 1930’s when good practice was to use a tape and transit, and they’ve been mentioned in textbooks for decades.
>NAD 29 and NAD 83
Picky point: You mean NAD27? The vertical is the one with the 29 in it..OK PK!
Who cares? I was driven nearly out of surveying, while this was being discussed.
The one that made it the hardest was RLS 882. He was banging out 1200 surveys a year, and hurtin me.
N
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