Geographers use a variety of tools to study the use of space on the earth?

The most common tool is a map and they also use photographs to gain visual evidence and the five themes of geography

Geographers use some of the same tools as other disciplines. However, there are some that are particularly tied to the spatial aspect of geography. Some of the tools are listed below. They are not comprehensive, but I think some of the most important.
1. Maps
2. GIS, Remote Sensing
3. Observations
4. Surveys
5. Mathematical models
6. Air Photos and other photographs

Its decreasing because of illnesses