Through a viewshed can identify the surface can be viewed from an observation point, ideal for the establishment of fire control towers, tourist observation points, establish the line of sight to relay communications towers, radar location , etc.
The Global Mapper application has the Tool Shed View, which allows to generate a viewshed, this input indicates how to calculate the area of visibility from a tower designed for bird watching, with a height of 15 meters and a radius of visibility 15 km, the location coordinates are UTMX 682120, UTMY 9540809 (WGS84 17S).
After running the Global Mapper application, load the digital elevation model, then open the View Tool Shed.
Mark the point of the observation tower in the View Shed Setup window, fill in the fields with their corresponding values.
Finally check if you have correctly completed all fields and accept, take into account the resolution of the digital elevation model largely depend on the quality of the desired results, the following image shows the surface with a range of 15 km radius includes the observation tower.