Echo base (BASE)

Figure 1. BASE example

BASE (also known as echo base) is the radar-indicated bottom of an area of precipitation. The system locates the lowest altitude of the defined reflectivity Threshold at each pixel location.

BASE displays the base level of detected signal echoes, which usually reflects the bottom of the cloud base or precipitation area.

As the following image shows, the minimum height above ground where echo bases can be detected increases with measurement range due to the curvature of Earth.

The opposite of the BASE product is the TOPS product.

Figure 2. BASE and TOPS products