You might already have a lisp routine that does the job, but if not a quick search on Google and the top result is this page from CADTutor which has the source for a lisp routine from the user Geobuilder. The next step is to use a lisp routine to generate 3D points from the text that identifies the elevations throughout the drawing. If you’re removing the redundant linework and only leaving points and text, once finished the before and after should look something like this If there is any MTEXT in the file, select it and explode it so it becomes regular text (DTEXT). You can remove anything from the DWG that isn’t a point or text if you like, but leaving the information in the DWG won’t affect the process. This will more than likely leave behind linework that isn’t required to generate your topography. My method is to freeze off unrelated layers and then copy and paste what remains to a new DWG file Using your preferred workflow, strip out all the information from the DWG file not related to the surface. The last thing you want to be doing is telling everyone that the data is rubbish because “these random spots I decided to look at are 5m higher than the surrounding surface, the surveyor must be wrong” Survey drawings could contain spot information for elements such as buildings, trees, fences and other non-surface information so you need to make sure that you’re grabbing only the information that is relevant to the topography surface. You need to have a really clear understanding of the data you’ve been given. Step 1 – Extracting the data from AutoCADįirstly you want to extract the usable information from AutoCAD. Before you jump up and down telling the surveyor to “Do your job properly” and demanding the file in 3D you might be able to impress everyone with your skills and get quicker results. in fact the surveyor sent you a DWG file with surface points at a 0 elevation. The problem is, sometimes you won’t get a DWG file with 3D surfaces and you don’t have a CSV file either. The two main options you have for automagically generating a topography surface are to either import from a DWG file that contains 3D surfaces – generally these would be topography triangles, or to generate from a list of points in a CSV file. Being an MEP guy, topography is one of those things in Revit I don’t deal with too often but the general concept of working with topography isn’t tremendously difficult.
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