how can i make topography(dwg) from sketch up by using google earth?
Use the File > Geo-location > Add Location command, which allows you to identify a specific locale on Google Earth that you’d like to “bring in” to SU.
SU creates two new layers in your model, one called Google Earth Snapshot and the other called Google Earth Terrain. The former contains a flat photograph, like the view in Google Earth, painted on a face; the latter contains the same photo, except painted on a contoured surface (TIN) representing the actual topography. You can toggle the display between them by checking or unchecking File > Geo-location > Show Terrain, or you can control the layers directly through the Layers dialog.
The photo and the TIN are each inside of a locked group on their respective layers. You can unlock either group, if you wish, and thereupon modify the contents of either. In particular, you can tweak the shape of the terrain or swap the image for another, and so on.
See: [Add Location] in the Knowledge Base.
Edit: Are you saying you’d like to derive elevation contour lines from the imported topography and export them as a flat contour drawing? That is the opposite of the usual workflow, of course, but do-able.
thanks alot.but i want to save topography map(show elevation in lines)t use in autocad
In short, create a stack of rectangles large enough to cover the entire area you have imported and spaced vertically at the interval you want for the contour lines. Superimpose the stack of rectangles on the terrain group–keep the rectangles outside the terrain group but occupying the same space. Now select the stack of rectangles, particularly the faces, but not the terrain group.
Now right-click > Intersect Faces with Model. Delete all the rectangles, leaving only the lines of Intersection with the terrain–those are the contour lines. Now bring all the contour lines down to the Ground Plane (you can use an extension called Drop GC to help with that), and, if you like, you can place all the contours on the Google Earth Snapshot and then export it as a 2D graphic. You need either SU Pro or a suitable extension to export in .dwg format.