How To Create Contours Using SRTM and Global Mapper
Socorro Island - Landsat Image Cleaned
Socorro Island - Marplot Map (1-100,000)
Socorro Island - SRTM-30 with Contours (50-meter interval)
Socorro Island - Google Earth Southern Detail (1-25,000)
Socorro Island - Marplot Map Southern Detail (1-25,000)
I took my original Socorro Island project and decided to add 50-meter interval contours. The process in Global Mapper is simple. First you need to load the appropriate SRTM-30 file which I snag from a NASA site. I get SRTM Version 2, which is the latest and greatest. The two files that makeup Socorro Island are titled N18W112.hgt.zip and N18W111.hgt.zip. GM allows these files to be loaded while zipped.
Once loaded I select "Generate contours..." from the File menu. I selected the default of 50-meter intervals. I enclose the area to create contours from and Enter. The contours are created within seconds.
SRTM is a fairly rough cut, consequently the contour closest to the shoreline wabbles in and out of the shoreline. The last step is to manually adjust this shoreline. All of you mapping pros wince when I say that I adjust manually. You appreciate that this adjustment is a W.A.G. (Wild Ass Guess) based on experience and practice.
What you see above is both the entire island with 50-meter contour intervals and a detail of the southern end of the island. I used Google Earth imagery of Socorro Island to create the exellent shoreline. I call it GEVS - Google Earth Vector Shoreline.
Like I have said, this creating of contours business is a snap with Global Mapper. Try it, you'll like it.
Enjoy!
Labels: EVS, Global Mapper, SRTM
