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Yoginathaswami

Topographical Map Creation

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Aloha, please share your thoughts, ideas or suggestions regarding the best work flow for this.

I am about to embark on a project of creating topographical map for our 70 acres monastery land. My first focus after collecting the survey data is to create topo lines showing the elevations. This will be used mainly for planning purposes. I learned to create topo lines using the DTM tool. (Thanks to Peter Cipes for teaching me). However, I am concern that this will create a giant file with all the 3D data.

My current thinking is to convert the DTM to 2D lines. (Need to figure out how to do this.) Then if I ever need to actually work on project that requires cut and fill, I would just model that portion of the property with previously gathered survey data.

Is this a right approach?

Thank very much!

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i think you are on the right track.

with too much information the dtm gets bogged down and unworkable. so, my first reaction is to make a simplified model of the whole site, using a greater contour interval--depending on the survey data you have--an greatly simplifying the 3d polys used to construct that dtm. this could be useful and fun to have for master planning, overviews, coordination, whatever.

then save the more detailed site date to create specific sites as you need them for design projects and construction.

cheers,

ray

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Yogi, With large sites I have no problem with the DTM if you set a large enough contour level (say 6') then when you need a more detailed elevation map of a specific area copy that areas data set to new DTM layer and reset elevations to say 6".

This is what I have done but there may be other solutions from other members.

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bryan,

do you mean altering the input site data, or changing the graphic properties of the dtm? my experience is that it is the complexity of the input data that makes a difference in the performance of the dtm.

ray

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Ray good point. I adjust the site model settings As for the input data I import loci generated by a total station so data is low. I have also had discussions with Yogi on this as he also has a Total Station.

As for other input data, yes lines and others could bog the system down.

What are you using as your input data?

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bryan, we use 3d polys we get from an engineering service in dwg format. but, one of my tasks this summer is to see what the local alternatives are, as we have had some problems with vw's ability to process a lot of inputs.

do you find in general that 3d loci work better than polys? any other suggestions regarding source site data?

cheers,

ray

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do you think converting the 3d polys to loci would make any difference? i've done that, thinking that it might be better. but, i don't have any conclusive evidence.

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Aloha,

Thank you so much for all the input! Bryan is correct...I've uploaded a lot points from my total station and file size stays pretty small. I always keep my survey points as a stakeout points in VW. What is 3D loci and what is the advantage of using it compared to Stakeout point?

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Yogi, I just read your post but running out to a meeting here in 10 min. Ill post on your question later tonight. I think your 3-4 hours behind so you shouldnt get it to late.

Later

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simplify 3d polys...yes, absolutely. especially with imported dwg contours.

i have reduced 3d polygons with well over 1000 vertices down to less than 100. multiply that by 50, 60 contours or more (we work on large, sites) and that's a huge reduction. you will find dramatic improvement with almost no noticeable loss in detail in the dtm.

careful though, the simplify 3d poly command can make some dumb decisions.

straying from yogi's question, bryan, have you ever imported site data in the form of .shp files from gis? something we are wanting to try.

cheers,

ray

Edited by ray isaacs

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If point cloud is desired (eg to make a DTM from a sub area of the greater site), contours can be "converted" by using Duplicate Along Path with each contour as a path, and a 3d locus or a Stake Object as the item to duplicate. Assign each set of loci or stakes to a class named for its height. Obviously, assign the loci or stakes to a separate layer, and generate the DTM from this data rather than from the original contours.

-B

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I input as 3D Loci (just a simple x,y,z) this generally is all I need (I can label the points by number and ref type also) this keeps the data small and accurate.

As for Stake Objects , I utilize them only for site modification and for stakeout or layout points that I can send back to the total station. This allows me to distinguish between survey data and layout data.

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Ray, yes I have and can work but files can get QUITE large. I haven't done this for a while though as I have found the data I collect generally tends to be more accurate. But also depends on the size of site you are working on. 1-20 acres no problem 100+ acres ?????

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With the Loci I just recently measured a job and had over 30K points and had no problem with the data or the DTM.

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hey, bryan. with 30,000 points, does mesh smoothing work?

i'm working right now with an imported shapefile for terrain data right now. the original has 92,000 points. i immediately reduced down to 14,000. mesh smoothing did not work. i incrementally reduced the number of points down to around 8000, before mesh smoothing worked.

could it be a difference in our computers? when i asked tech support about that some time go, they said hardware wouldn't make any difference. but, i seem to be the only one on this board constantly having this problem.

cheers,

ray

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On that particular I did not mesh smooth. I only used it for topo elevations in a DTM. and yes with more points comes slower DTM. It was noticeable but not by much.

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