I need to acquire a very detailed topographic map of Istanbul, Turkey without any markers. Do you know such sources who provides these kind of maps? I tried to Google it, but the results were far from satisfactory. I found world topography from NASA, some low resolution images that does not worth much. There are a lot for US but unfortunately I failed to find one for Istanbul.
Actually since I don't the details of GIS, I don't know the technical terms to explain what I am looking for. But here is what I'll use the map for: I am going to print 3D version of Istanbul using some 3D printer, and display visualizations on top of it using projector hooked on the ceiling. In this case, I assume that I need either a 3D point cloud, or a 2D height map where I can deduce 3D points after some processing.
Best Answer
What you're after is a Digital Elevation Model (DEM) (wikipedia) which represents surface elevation as a single band raster (i.e. your 2D height map).
One starting point for getting DEM data is the USGS EarthExplorer data portal (http://earthexplorer.usgs.gov/) which allows you to select a region and search for data. If you use the map to zoom to Istanbul and the area you're interested in click the
Use Mapbutton to select your entire map view for data. In theData Setstab expand outDigital Elevationand selectASTER GLOBAL DEMwhich is 30m resolution DEM data. You may have to stick some scenes together as I believe the tiles neatly bisect Istanbul, but it will hopefully be enough to get you started.