Here's the situation: you have a bunch of GIS data with extensions like .shp and .xml and you know that its got to have elevations and topography in it because the damn file is labeled new_york_contours. But you're an architect, and you don't really know GIS that well, and you want to convert the GIS file to something you can take into autoCAD. Here's what you do.
- First of all, you'll need arcMAP, which is a program. There are other programs for handling GIS data, but this is what I'm using. Start with a blank template.
- Add your data. Click on the icon that looks like a bold black cross superimposed over a yellow diamond. This will give you a directory that none of your stuff is in, so you need to find the icon in that window that says "add folder location." Click on that to find your folder which contains the data you need. Open up the data. I usually use the shapefile, which has a .shp extension.
- This data will come in as a layer by name ( "new_york_contours") on the left layer window of the screen and you should be able to see it. If you don't see anything in the main window, like a topographic map of new york, make sure you're zoomed to the extents by clicking on the globe icon at the toolbar on the top.
- Right click on the layer in the layer window on the left, and say "open table attributes" or something like that. A giant spreadsheet will pop open.
- Look for a column that has elevation data in it. Usually it will be called "ELEVATIONS" or "HEIGHTS" or something like that. If you don't see any columns with data that makes sense for elevations, you're out of luck since it means the file doesn't have elevation data as part of it. Once you locate the column you're looking for, go ahead to step 6.
- What you are looking for now is a table column called "LAYER." if it has it, you can skip down to 10 If not, continue to 7. It's almost like a "Choose your own adventure" book.
- Up in the top left corner of the spreadsheet thing there's a button called "add field." click it. You're going to basically create a new column for your spreadsheet. Give it the name LAYER and use "short integer" as the drop down menu. Click ok.
- You should now see the new column. Mouse over the word LAYER until it turns into a down arrow and click to select the entire column. It will be empty. Right click on the word LAYER and select "Field calculator" which will add values to this column. In field calculator, the left hand pane will show the columns of the spreadsheet. Double click on the one that has the elevation values, and it will appear in the panel below. Make sure "number" is also selected, although it should be by default. Click ok.
- It may take a few minutes but then the LAYER column should have numbers in it, and if you did everything right, the numbers should be the same as the ones in the elevations column. Click ok.
- Open up the arcMAP tool box. Its icon has a tiny red tool box. Open up "conversions" and click on "convert to CAD". It will give you a new window. Drag the named layer (new_york_contours) from the left handed panel with the layers into the new window to add it to the layers for export. Specify where you want the file to be saved and what version of CAD.
- Click ok. It may take awhile to export the data. If it works, you will see the same layer of data overlaid in a new color over the old data, so you'd see a green new york contour map over a red new york contour map, for example.
- Open the CAD file and the check the layers. If everything worked, each topographic level should now be on its own layer.