arcscenedemsrtm
I have downloaded some SRTM Dem files here: http://dds.cr.usgs.gov/srtm/version2_1/SRTM30//srtm30
They are from the USGS site.
I would like to export them as 3d.
I have ran through a few tutorials online, e.g.
http://prod.library.utoronto.ca/maplib/3D.pdf
But still don't get it.
Question:
http://dds.cr.usgs.gov/srtm/version2_1/Documentation/Continent_def.gif
You can use http://www.latlontoelevation.com/ lat/lng to get the Shuttle Radar Topography Mission (SRTM) data too.
Here's what the original NASA's SRTM document says (emphasis is mine):
File names refer to the latitude and longitude of the lower left corner of the tile - e.g. N37W105 has its lower left corner at 37 degrees north latitude and 105 degrees west longitude. To be more exact, these coordinates refer to the geometric center of the lower left pixel, which in the case of SRTM3 data will be about 90 meters in extent.
What you have is an ASCII grid file. I've seen two types of these: one type defines the grid using xllcorner/yllcorner, the other using xllcenter/yllcenter, but both are essentially the same.
So, with that in mind, and seeing that I need to map each elevation to a point. Is it more accurate to say that the first value in the grid represents the elevation at (xllcorner, yllcorner) or at (xllcorner + cellsize / 2, yllcorner + cellsize / 2)?
SRTM height represents the (average) height of all points within the cell, which has a bounding box (xllcorner, yllcorner, xllcorner + cellsize, yllcorner + cellsize). The center of that cell is xllcorner + cellsize/2, yllcorner + cellsize/2. So, basically, the answer to your question is: use the center of the cell to represent the height point.
I would also suggest running some TIN simplification algorithm on your mesh to reduce its size, that's what I did for my project.
Best Answer
When you downloaded the data what format did it come in? By definition, if the data is a raster format, it can be considered 3D data, as it has a x,y,z value. If you are looking to have it extruded in ArcScene then you will want to do a few of the following things.
Assuming your data is in a usable raster format (ie: GeoTiff) then you will want to do the following: - Open the Properties of the data in ArcScene and change the Symbology (ie: Standard Dev. 2 and change the statistics to From Current Display Extent - On the Base Heights Tab change the radio buttom from No elevation values from a surface to Floating on a custom surface and choose the SRTM raster file (this will make the raster have 3D visual appeal - Finally you can play with the visual rendering which is located under the Rendering tab. The Higher the rendering, the more memory it needs from your computer and graphics card.