I’m constantly amazed at how many people import data from Google Earth into Civil 3D and then complain about how horrible the data is. There are two primary issues that I’ve seen when importing data from Google Earth. First of all, the imagery is inconsistent at best. The guys over at Being Civil wrote up a nice post about this issue HERE if you are interested (also, the images come in black and white). The surface data that you bring in is very limited. Sure, you can pick anywhere you want but you are limited to importing 5,000 points and, if you have a large area, that’s not very much data at all (I recently downloaded a DEM file with over 2.5 million points, now THAT’S data!). So, instead of relying on Google Earth, go out and get the data yourself! You’ll be much happier with the results.
For those of you with projects in the United States there is an amazing resource that I was familiar with but never really investigated much, the USGS Seamless Data Warehouse (I was playing around with the Autodesk Infrastructure Modeler and looking for data). You can find it at seamless.usgs.gov. Here you can browse a map to find your project location and download orthoimagery (i.e. aerial images) as well as surfaces (DEM files). You’ll need to create an account to download the data but it’s free.
Using the Seamless Viewer
When you get to seamless.usgs.gov, on the left hand side, there is a panel and on this panel, is a link to the Seamless Viewer (you can access it HERE if you like). It looks a little something like this:
Once you click on this, it will take you to a map showing the entire United States (well, most of North America actually). Draw a rectangle around where your project is (you’ll see the state boundaries so use that as a guide and zoom in on the state the project is in). Once at the state level, you’ll probably need some assistance locating your project area. On the right hand side of the map, you can change what is being displayed in the map. By default (at least for me) all it showed was the digital elevation data. That really didn’t help me find the area I was looking for (Colorado is a big state, not as big as Texas of course, but still big) so I toggled on a few options to help me locate my project. The ones that seemed to help me the most were the Orthoimagery, the Transportation, and the Places (Names). As you can see in the following images, it makes a huge difference.
Once you get zoomed in on the area of interest, you need to tell the Seamless servers what it is you want to download. On the right side of the map where the Display options are located, switch from Display to Download.
In this case, I chose to download the NAIP (National Agriculture Imagery Program) Orthoimagery as well as the 1/3 second DEM from the National /Elevation Dataset. Once you’ve set what it is you want to download, you need to specify what part of the map that you want the data for. To do this, use the tools on the left side. I chose the “Define Rectangular Download Area” option.
A new window will pop up with links to download each file. The files you’ll get are simple .zip files. Once you unzip them you’ll get a ton of data. For the DEM, the files you need are the ones that end in .adf. Just keep all these files in one location and you can then create a surface from them in Civil 3D. The images will have a lot of files as well but really the only ones you need are the .tif file and the .tfw file. The .tif file is the actual image itself and the .tfw file is the world file. The world file lets Civil 3D properly locate it in your drawing. And honestly, I don’t think you really need the .tfw file as .tif files can have coordinate information embedded into them (aka GeoTIFF). I would still just leave them together to be safe.
Using the Data in Civil 3D
Once you have the data, you need to add it into Civil 3D. First thing you want to do before adding in this data is to make sure your drawing has a coordinate system assigned to it. If you aren’t familiar with this, simply right click on the drawing name on the settings tab of the Prospector and choose Edit Drawing Settings. On the Units and Zone tab, assign an appropriate coordinate system to your drawing. If you aren’t sure what to use here, check with your surveyor on the project.
To bring the DEM file into Civil 3D, create a surface and add the DEM file as data. I’m not going to get into the details in the post as I’ve already talked about how to bring DEM files in to Civil 3D. You can read it HERE if you like. When you add the DEM file, use the coordinate system code LL83. Also make sure you read the comments as you’ll need create the surface in a metric drawing and use LandXML to bring it into a drawing that is in imperial units.
To bring the images into Civil 3D, use the Map Image Insert command MAPIINSERT (yes, two I’s in there). This will bring the images in georeferenced.
Sure this process takes longer then importing from Google Earth but think of it this way, “You get what you pay for”. In this case, you’re paying with time. Importing from Google Earth is fast but you get very poor data. Getting the data yourself takes a bit longer but you get MUCH better results. Check out this example, in the following image you can see where four of the images downloaded from the Seamless server line up and it’s REALLY close to being exactly matched up (I can’t see any offset or other error personally). Compare that with what you get out of Google Earth.
If anyone has data sources similar to this for other countries, comment here so others can find them.