One of the things I run up against all the time in my work is helping people through the process of importing aerial imagery into Civil 3D. More and more, I find that my design teams are looking to save time and money by using aerial photos as the basis of their concept and preliminary designs. It makes perfect sense when you think about it. Why spend time and money developing a scale drawing of s site’s existing conditions when the project may never happen? Even if it does, how exact do you really need the existing site to be in order to give the client an idea of what you might be able to do on a particular job?
The problem on my end is that users often have to struggle to locate imagery to use for the background and even when they find it, a lot of drafters aren’t sure how to bring it in at the correct scale and coordinate locations. There are a lot of software packages out there that handle this functionality, such as ArcGIS, Autodesk Map and Raster Design. All these are great packages but they require some training and a bit of effort on the part of the drafter to get them to just what you need. Wouldn’t it be nice if you could just use a simple program that almost the entire world is familiar with and let that handle all the messy work? Well, you can, it’s called Google Earth.
Autodesk and Google Earth have collaborated on a simple tool inside of Civil 3D that allows you to import GE Images directly into your plans. No, I’m not talking about cheap screen captures here; I mean the full blown aerial imagery GE is noted for. Not only that, but when you import these images, they come in at actual size and in the correct coordinate locations. How’s that for simple? The only drawback to the process is that you are limited to importing the GE data as grey scale images instead of color. Apparently, there was a plug-in available for a while that let you do color but Google and Autodesk had some disagreement over it and it got pulled. Still, the grey scale images are a fantastic tool for general construction documents, which are almost always black and white prints anyway.
Now, let me really blow your mind. Another function my firm has spent a lot of money on over the years is getting an existing surface (TIN) put together on which they can base their proposed design. We’ve paid for aerial topography firms to generate preliminary surfaces, spent time piecing together rough surfaces from older plans and other drawings and dozens of other methods for getting a starting surface put together quickly. Well, GE and Autodesk have answered this problem for me as well. Not only can we import the imagery from GE, we can also import a fully developed 3D surface of the area we need. Now, it’s not the most refined surface in the world, but for a preliminary design, it will work just fine. As best as I can tell, the GE surfaces are only accurate to within 10 ft. +/- , certainly not enough for a real design but if you’re just looking to get the general slopes on your site, or do some rough cut/fill calculations this function can save you tons of time.
So, how does it work? It’s as simple as could be: first, run Goggle earth and zoom into the area that you want an aerial image and/or surface of. Note that the data that we will bring into AutoCAD is exactly what is shown in your GE window. Next, just open an AutoCAD drawing and make sure you set any map zones or coordinate systems you want to use. Now, just go to the Insert tab on your ribbon bar and click on the “Google Earth” option (above). In the drop down menu that appears, choose the option that works for you:
Google Earth Image: Inserts a grey scale image at the correct size and coordinate location into your drawing.
Google Earth Surface: Inserts a fully built C3D Surface of the area you have displayed in Google Earth into your drawing.
Google Earth Image and Surface: Inserts both of the above, in effect giving you a nearly complete existing site plan in moments.
Google Earth Mesh: Creates a 3D Mesh, with real elevations at each vertex point, at the correct coordinate locations for your site.
There you go; it’s as simple as that. What used to take hours to develop can now be done in just a few seconds. Not, that is what I call progress!