Setting Topographical Surface To AutoCAD

[Anonymous]

Hi,

I have a topographical survey done for a site I am working on and want to create a Revit topographical surface to match the results. 

I have imported the AutoCAD into Revit and drawn a surface on. When I click on each point to set the height of the point the numbers are not as they should be within the project. For example, my ground floor is set at 39.245m. I have put points of my surface just below this but they are displaying at an elevation of 825? I am struggling to find any correlation between the two. 

Any help would be appreciated 🙂

[Anonymous]

@Anonymous is your file in mm? it almost looks like it is reading the elevation heights in inches and showing you in mm. Try a spot elevation tag in 3d set to the same units and see what the read-outs are showing. Also, I have a dynamo script that allows you to convert Autocad elevation text to topography if you would like it. 

[Anonymous]

Hi Dennis,

Yes my project is measured in mm. I am unable to do a spot elevation for my topography for some reason, Revit just won't allow it. If you look at the below picture however you can see the footer level of my buildings set at -225mm with the topography surface very close to it.

That sounds like it could be very useful. Is it as straight forward as it sounds?

[Anonymous]

Picture I forgot to attach to my reply:

[Anonymous]

@Anonymous This is how the script works. There are 2 methods with this script:

1) Import a Cad file with only the Elevation Text Layer to Revit

2) Explode the Cad file and convert all elevation text to "ELEVTEXT"

3a) Run the Script with Topography.Bypoints

3b) If 3a does not work, Run the Script with Write to CSV, then create toposurface in Revit using the CSV file. 

Just make sure to set your units in Revit to the same as the elevation points before running the script. Have fun!

OVERALL SCRIPTOPTION 3A AND 3B

[Anonymous]

thank you for sharing this :).

initial question, how do you convert the text once it has been exploded? 

[Anonymous]

Just create a new text type called ELEVTEXT, select all instances in view and swap to new text. If you isolate the cad file before exploding, you can just select all and filter the text, swap to ELEVTEXT

[Anonymous]

thank you, i'll give this a try and get back to you 

[barthbradley]

It sound like you are creating the Toposurface in Revit by placing points on top of each point in the CAD import, and entering the the point's elevation that is called out in the CAD? Am I reading you right?  

If so, bear in mind the Toposurface's zero origin is the Internal Origin in Revit. It is not related to the Project Base Point or Survey Point.  So, if that is your workflow (e.g. placing points on top of CAD points) , then you need to move the Toposurface to its correct elevation in the Project after you create it.  

[ToanDN]

If the topo is done by a professional then chances are the CAD file they have provided you have all the points at proper XYZ coordinates.  You can check by open it in CAD, go to an elevation or 3d view and see if the points are 3D, or select a point and see its Z value from properties.  If that is the case, you can simply create the topo from Import by linking teh CAD file in Revit with the Current View Only box UNCHECKED.

Also, you can always ask the surveyor to provide you with a point file (TXT or CSV format) and create the topo from it.

[Anonymous]

@ToanDN Oh how i long for that day! 🙂 85% of the time, the surveys we receive are pdf, or at most a flat 2d survey in DWG. If its a brand new lot, we can sometimes get lucky, however even with the better surveys, they come with AEC objects, annotative points, Civil 3d exported blocks, etc. So far this script has been a huge time saver for us at WZMH,  especially for smaller custom home design firms, where they deal with so many variations of surveys. The odd time that we do get a CSV file or contour/points dwg file is really nice though. We need to start education the Survey teams on the best formats suited for architecture. 

[Anonymous]

Hi Brad,

That is correct and was my initial intention. 

So by what you are saying Revit's Internal Origin is not movable? Due to this I should;

1) Create the surface and raise each point to its proper position. (This will then move my surface far above my existing model and CAD).

2) Move my model and CAD relative to the created surface.

3) Adjust my Survey Point and Project Base Point accordingly.

[Anonymous]

Hi Toan,

The topo has been done by professionals and everything does seem to match up correctly in the z-axis. 

I had tried the create from import but was unsure on the accuracy of it as the imported surface I was getting felt wrong somehow. The "points" had not gone in as points, instead each "point" had gone in as a square as you can see here:

As the points do not measure in meters above sea level I can't think of a way of checking the accuracy of the surface. e.g. the below image should measure at 39.696m, but in my Revit project measures at 948.2. If the measurement was matching then I would have confidence that the surface was correct etc, but as they do not I'm unsure on if the results are right.

My problem also furthers when I want to place the surface in relation to the buildings. Lets imagine I want to sit all my buildings 39.8m above sea level. How am I going know where 39.8m above sea level is if the surface points measurements do not correspond correctly. 

[Anonymous]

Image missing from this post:

[barthbradley]

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@Anonymous wrote:

As the points do not measure in meters above sea level I can't think of a way of checking the accuracy of the surface. e.g. the below image should measure at 39.696m, but in my Revit project measures at 948.2. 

Change your Project Units to Meters + 3 decimal spaces.  

[Anonymous]

Hi Brad,

i'm confused how this would help? The measurements still do not match

[barthbradley]

The Points' Elevations inside Toposurface sketch mode are always relative to the Project's Internal Origin, and have no value or significance outside of sketch mode. If you were to place a Spot Elevation on that exact Point outside of sketch mode, it's elevation reading would be relative to the "Elevation Base"  of the Spot Elevation (e.g. Survey Point or Project Base Point).   

[Anonymous]

Hi Brad, 

Yeah I discovered earlier that I am able to do a spot elevation that measures from the survey point. It read that the surface all measured 300mm below what it should so i just moved the surface up 300mm.

I'm hoping this is now in the right place? I am now trying to draw a road on my topography as well as a path which is proving very difficult. The path is to be 125mm above the road at one side and the sloping 25mm upwards towards my site. The reason this is proving a pain is because the levels of the road are all over and its hard to get my path 125mm above every point exactly. 

[Anonymous]

take this picture for example;

Is there anyway to offset a split surface in elevation or anything of similar? Something of such would make this 100 times more accurate and easier (the bright colours are for ease of distinguishing each split surface). 

[barthbradley]

Split Surface?  That's out of left field.  How does that relate to your previous questions?  I'm lost. But, regarding "offsetting" a Split Region; I wouldn't.  Why do you want to?  What are you trying to accomplish?