Google Earth Terrain to DVSP
A number of CAD and GIS applications feature the ability to export CAD data to Google Earth, but some applications can also capture 3D Google Earth DTM data. This 3D DTM data can then be used in DVSP to form some approximate ground data (although the accuracy may be unreliable).
Microstation, PowerDraft and the MX CAD Engine all have this functionality (AutoCAD may do as well, but I’m not sure ??).
Here are some simple steps to do this:
The Google Earth tool box can be loaded from the following menu “Tools > Google Earth”.
Link Google Earth to CAD application
There are a number of ways to accurately define the geographic location of your CAD data including:
a. Using a single Placemark to define the location of a known point
b. Using the Geospatial Extension application (Geographics) to handle the geographic projection
c. Place two or more Placemarks to provide the complete projection transformation
The first of these methods is the simplest to use and is outlined below (its worth noting that this is probably the most inaccurate method):
1. Open Google Earth and create a single Placemark. This must be in a location that is commonly known to both Google Earth and the CAD application. i.e. known co-ordinates.
2. Save the placemark as a “kml” file, by right-clicking on the created placemark and choosing “Save As”. Save to a logical place as you need to browse to it in the next step
3. In the CAD application, use the Define Placemark Monument tool to define a monument point that matches the location of the newly created placemark.
4. Once you select a point on the CAD display, a Select Monument Placemark File dialog box is displayed, and you point to the newly created “kml” file. This now links the CAD application to Google Earth.
Export CAD data to Google Earth
You can then use the Export Google Earth (KML) File tool to export your CAD data to a new Google Earth “kml” or “kmz” file. This will be the file that stores all you CAD entities, imagery, and reference data. This is the file you can send to others.
Capture 3D Google Earth DTM Data
You can then Capture a Google Earth image: This tool allows you to not only capture the imagery from Google Earth, but also capture DTM data from Google Earth.
The Terrain setting in Google Earth must be switched on for this tool to work. The amount of zoom used on the Google Earth display determines the extent density of DTM data which is exported back to the CAD application.
Hit the icon, set the data point on the CAD display, and the DTM data will be exported to a 3D mesh (CAD entities) to the CAD application.
From there, its a simple process of importing the 3D mesh to Dynamite VSP via a Civil Application (LandXML, GENIO, Model.fil etc) or even just a DWG. There are various methods to thin or reduce this type of data, which I can outline in another post if anyone is interested.
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