Compare Points Perpindicular to Surface

[Anonymous]

Hi All,

Just wondering if anybody has a solution to my problem. I am working on drawings where we create dtm's from surfaces, use the dtm for layout, shoot the asbuilt of the final surface, and then compare hundreds of shots to the surface to develop an as-build report.

I want to be able to select a mass of points, compare the perpindicular difference in elevation to the surface, and have an excel spread sheet generated from the results.

My coworkers are able to do this in Terramodel but I am on a mission to eliminate Terramodel from my day to day work.

Just hoping somebody may have come across this before and can shed some light as to what commands or add-ons are availbable. I've never worked with a LISP but i am certainly open to suggestions at this point.

[BrianHailey]

Hi Andrew, I don't have an answer for you but I'm curious. I've never heard of anyone wanting such a thing. What do you use it for?

[Anonymous]

Currently I am working with a survey department. We are contructing a powerhouse and intake for a hydro project. The project consists of many sloped, curved, and spiraled surfaces. Once the concrete is finished on these surface, the surveyors take hundreds of shots to check the final surface for conformity. It is my job to process the shots and compare them to the design surface.

The only way I know to do this is set up a ucs in section view, convert the slopes, curves, and spirals to feature lines, and dimension each one individually. Then I have to switch to plan view and label each one individually. It is unrealistic for me to do this and I am not interested in learning how to use Terramodel.

Hope this answers your question and sparks some more interest in somebody who may have a solution!

Thanks

[wfberry]

Back to your original question.  Surely you do not mean perpendicular distance to surface but vertical distance.

Bill

[Anonymous]

Yes I'm looking for the elevation difference at the same nothing and easting. We dimension them in section view as aligned with a perpendicular snap so I guess my statement may seem confusing. In saying that, is there a way to determine the difference in elevation between a point and surface at the same northing and easting? And also, can I do this with hundreds of points and have c3d develop a spreadsheet with the results?

[JeffPaulsen]

Create a TIN surface from your as-built points. Then create a TIN volume surface from the design surface and the as-built surface. The volume surface will give you the elevation difference at each as-built point. Make a copy (not sure the best way to do this) of your as-built points and assign elevations from the volume surface. Now you have points with the elevation difference.

[Anonymous]

I haven't tried this exact method but I will. However, I did try elevating points to design surface, re-importing the points with new numbers, exporting a points report, and then taking the elevations from the elevated points and comparing them to the original points.....but the numbers did not match the dimensions given manually through c3d or the report generated through Terramodel. Does creating a tin volume surface differ from the method I have tried?

[JeffPaulsen]

The methods should produce essentially the same results.

I think the reason you are getting different results is because you do not have as-built points at the exact location as the design points. You are relying on a surface to interpolate elevations at the corresponding points. I would assume Terramodel and C3D have slightly different ways of creating the surface therefore the elevations will not be them same at all locations on the surface.

[TerryDotson]

Get the MapWorks Points 21-day demo and use it's Add Difference Points routine.  Works directly with Surfaces in Civil3D and AeccPoints.

Dialog Example: http://www.dotsoft.com/images/mwpntdif.png

[AllenJessup]

We used to do something similar for stakeout. It depends on point sequence. We would stake point # 1114, set the stake and shoot it as point 2114. The point sequence can be anything. We would then export a CSV file for the shots on the stakes of just point # and elevation, do the same for the proposed. Paste the stake point # & elevations in to column A & B and the proposed point # & elevation in to column C & D. Than just subtract column D from B. So you have the proposed in one column and the as-built in another. The shots don't have to fall exactly on top of each other since you're not even using the coordinates.

The point numbers don't have to be exactly 1000 apart. They just have to be in increasing order. But we set it up that way to make it easier to spot if we missed a point in either sequence.

Allen

[Sinc]

Here's another third-party option:

http://www.quuxsoft.com/SincpacC3D_Help/SP_DisplayPoints.htm

You should be able to also manage it in C3D without third-party help, using techniques like the one Jeff mentioned above, but it's a lot more time-consuming.

[Anonymous]

Just a little update. After trying and combining the suggestions everybody posted I have found a way to do this that gives the same results as terramodel.

Import as-build points (CSV) into drawing. Elevate points to surface used for design DTM. Export points to a new CSV. Copy elevations from one elevated points CSV to the as-build point CSV, subtract the elevation differences and you have all the deltas for each individual point.

For display, I create a new CSV with the deltas as the description, import into C3D and display the description.

Thanks everybody for the help and suggestions. I would not have figured this out without them.

[Joe-Bouza]

I didn't read the rest of the post but those results are the same as updating elevation from a volume surface of EG vs As-Built.

[neilyj666]

The results will be the same but you will need to do some manipulation with points if you want to get the differences tabulated i.e. level differences at specific locations

[Sinc]

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@Joe-Bouza wrote:

I didn't read the rest of the post but those results are the same as updating elevation from a volume surface of EG vs As-Built.

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The confusing thing about that is you need additional points.  Typically, you don't want to change your Survey point elevations.  So you don't want to just select your Survey points and adjust their elevations to match a Volume surface.  And creating copies of those points just adds clutter.

But there are options...  As I said, you may not NEED third-party support like what we and Terry offer, but it can make your life much easier...

[Anonymous]

In the method I described earlier, the dealings is more with the CSV's than with the points in the drawing. You elevate them once and then delete them as soon as you export. I have tried some third party software and i can not find anything that will generate the delta's and produce a report or points with attributes that represent the deltas.

[neilyj666]

Copying the required points to a new point group e.g. Deltas and then elevating to the TIN volume surface (might have to create a new surface and paste the TIN volume surface into it for this to work) will allow you to create a C3D table of XYZ of the points of interest where Z will be the delta value.

If you need this in Excel then C3D tables do not lend themselves to doing this unlike vanilla ACAD tables. It is possible by exploding the table and using a lisp to create a vanilla ACAD table and then exporting to Excel.

[Anonymous]

I do not create a TIN volume surface to complete this process. I just simply elevate the points to the surface I used to create the DTM and export them, then compare them to the points taken in the field. It is a very simple way to do this. Creating a TIN volume surface seems like an unneccassary step in the process.

[Joe-Bouza]

Not for nothing but a desire to not make extra points sounds silly -Not saying Terry's and your app dont look useful, they seem very usefull.

But..... Do you want to save the changes to the file (yes / No)

Choices, life is all about choices

[Anonymous]

I agree. Life is about choices. What would be ideal is a report than can be created where you select the surface and the points you want to compare and it spits out an xls worksheet with the required info. I have been speaking to some people who say this may be possible in the future but I have not had any positive results.

For me it's about keeping it simple. Importing, exporting, and deleting points is a very simple way to get this task done. However, I would much rather see a solution that is specifically designed to produce these results without creating extra points or surfaces.