Global Mapper can easily obtain geographic information from different sources, in a simple way. To create contour lines anywhere in the world, you must first review the metadata. In this example data AsterGDEM used, but have a resolution of 38 meters, therefore it is not recommended to place a lower range.
Open Global Mapper, in the home screen go to Download Free Maps/Imagery from Online Sources, opens a new window with information from various servers to rise in TERRAIN DATA select ASTER Gdem v2 Worldwide Elevation Data (1 arc-second resolution) this process requires an Internet connection, but you can also use a digital elevation model stored locally, to do this, select the first option Open Your Own Data Files.
Global Mapper allows only visualize the area of interest, without the need to download the data. As a suggestion, not recommended to generate contour lines to create a TIN, DEM first download directly, then convert it to TIN (this was a concern and frequent activity performed).
Then with zooming and panning tools, navigate to the site of interest. Go to the menu Analysis select Generate Contours (from Terrain Grid).
In the Contour Options tab, Contuor Interval section, you can customize the interval and the unit to generate the contour lines, as well as minor and major contours. Other options can set the elevation range and resolution. By default Global Mapper create contour lines based on the current screen view, but you can be changed from the Contour Bounds tab and click the button Draw a Box.
Draw a box in the study area, accept the settings in the active window to generate a new layer with contours, although this is the basic process in this activity, playing with the other options available allows for further customization of desired product.
To save contours and open in different applications, it is preferable to save as shapefile, for it from the toolbar click Open Control Center, select only the contours layer, then go to the menu File > Export > Export Vector/Lidar Format > Shapefile > Export Lines, select a name and directory.