Not an expert by any means but remote sensing is basically a method of surveying the characteristics of an area without contacting it. This is usually done by plane or satellite from above.
Remote sensing has a number of applications such as land surveying, topographic maps, planning a construction site, as well as military and intelligence uses.
Risk assessment depends on what task you're trying to accomplish.
If you want to build on a certain area, remote sensing can be used to reduce the risk of building on unstable terrain or on topographically undesirable locations by exploring the area virtually ahead of time in a computer simulation created with aircraft or satellite imagery.
In the case of military and intelligence purposes, remote sensing can be used to establish a general understanding about the geographical characteristics of a location to see where the enemy could be able to hide and conduct a surprise ambush or to evaluate certain terrain and select the best route for the invasion of a specific area.
