Hi All,
I am working on an archaeological project using a Spectra Focus 8 total station with Survey Pro 4.11. I am attempting to layout a 50-meter interval grid over a 2000 m by 2000 m area. All of my previous total station work has been solely with data collection. Uploading and staking-out points is uncharted territory for me. I have created a .csv file in excel with the desired horizontal coordinates, and can upload it and view it in Survey Pro with no problem.
My main question is what I should do with the vertical coordinates in the .csv file? Do I assign it an arbitrary elevation like 1000 m, 0 m, or leave it blank (which defaults to 0)? Obviously, the elevation across the site is not uniform and I am concerned as to how the total station will respond. Will there be any sort of horizontal distortion of the grid due to changes in topography?
I will also be collecting numerous additional points on features that I would like to reference to the grid points (my start point being N 5000, E 5000, Elev 1000). The end goal is to produce a nice map with the grid points referenced to real world features that I shoot in and I don't want the elevations to be all funky.
Thank you in advance for whatever input you can provide.
-Dave
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Replies
Dave,
How precise does this grid need to be?
What kind of stakes are being placed at the grid points?
Will you be doing all the calculations inside Survey Pro without the aid of a CADD program?
I like Arnel's method, but I'm not convinced that your project would require the degree of precision that it would afford you.
Scott and Arnel,
Thank you for your feedback on my questions.
The purpose of the grid is really to set up regularly spaced artifact collections across the site. I'll just be putting in pin flags every 50 meters based on the grid and a field crew will be collecting artifacts around those flags. I will also be mapping in numerous architectural features in relation to the grid. Other than the Spectra, I have a Trimble Juno ST which I'll use to shoot in control points (with the full knowledge that I'm only going to get 2-meter GPS accuracy at best).
I do not have access to AutoCAD (or really know how to use it) so I'm basically working in a world of excel sheets. I've been able to bring everything into ArcGIS, Foresight DXM, and SurveyPro and everything looks good.
With regards to precision, of course the more accurate the better, but I pretty sure that the director would be happy with sub-meter accuracy across 2 km. As long as I am not using the grid points to map, and re-shoot the the staked points in the field to generate elevations should I be okay?
Scott, thanks for the offer to talk over the phone, but the project is near Mexico City and really only have access to internet.Thanks again for your input. It's really helping me develop a better understanding both pre- and post-processing. The last company I worked for had a GIS department, so all I was really responsible for setting up the station and collecting points.
Sincerely,
Dave
Hi Dave,
With that accuracy requirement, I guess your procedure would suffice.
Cheers and good luck!
Regards,
Arnel
Dave,
As long as sub-meter horizontal accuracy is okay and elevations are irrelevant to the data you collect, all I would do is assign an elevation like 5000 to your starting point and backsight point where you will begin your grid layout which will not cause anything to go below zero elevation, I think it sounds like the grid will be laid out okay. It would be good practice, however, to maintain a consistent vertical relationship between points that you occupy with the total station. This means entering height of instrument (HI) and height of target (center of prism on rod or tripod) and then checking them by using the (By Distance) method, which will also display the vertical error during your Backsight Setup.
Does all that make sense? Sometimes I'm not sure if it comes out the way others can understand.
I wish you had a MagicJack Call from your magicJack from any country to the U.S. and Canada and the call is free. MagicJack uses the internet to make phone calls, costs about $40 and includes one year of service (after that your phone bill is $20 per year because you already have the hardware which you plug into USB and use a computer headset or just plug any phone into the hardware.
Hi Dave,
Surveying a 2km x 2km area requires working knowledge in Geodesy. That is if you want map accuracy. I you want to stakeout a 2D grid on ground, you need first to realize that what you have on map is not what you get on ground and vice versa. This is due to map projection process. In addition, elevation surely affects mapping procedures.
If you ask me on how I'll do it using total station, the following approach should be fine:
1. Establish geodetic control points using GPS/GNSS.
2. Develop control network traversing through GPS/GNSS stations.
3. If you require some localization to promote ease of work, you can do it but not necessarily.
4. In AutoCAD Civil 3D or any other CAD system that supports mapping, assign the required projection system or the zoning specifics/category for the area to be surveyed.
5. Draw the required georeferenced grid lines and generate the intersection points to be stakeout with initial zero elevation values.
6. Employ Microsurvey Star*Net. Perform rigorous Least Squares Analysis. Generate local coordinate values. Employ local coordinate values of stations during the stake out work using total station. This means that scale factors and convergence issues are already embedded in the local coordinate values.
7. Upload to total station the local coordinate values of control stations and grid points.
8. Stakeout the grid points.
9. Measure the actual grid points to determine actual elevation.
10. Download measurement data and perform Least Squares Analysis if necessary.
11. Perform mapping.
12. Cheers!
Hope this helps.
Regards,
Arnel M. Domag
nth geographics and geometrics
David, I have been familiar with Survey Pro since Survey Pro became Survey Pro. However, I would need to know which CAD platform you are using to be able to answer some questions that you have. Almost certainly you could use utilize Microsoft Active Sync to communicate between your field equipment and your computer. As far as your concerns about vertical discontinuity, proper measurements in the field, such as the height of instrument and height of rod or target play a vital role. You may say, yes, of course, but perhaps a good chat would be in order, since I am not sure exactly what other underlying circumstances may be playing into the scenario in which unless I may understand it in it's entirety, I may not become a good advisor. I am available by phone and am very interested in answering your questions. Should you want to contact me by phone, please visit my page and send me a message.
Thank you for your contribution.