Changes in this quantity are associated with changes in radar reflectivity in a form of interferometry whose control variables are “persistent scatterers.” Measurements of this quantity standardized to the GTOPO30 (“G-topo-thirty”) system have since been improved by the ASTER instrument. (-5[1])Techniques like IfSAR (“IF-sar”) and InSAR (10[1])(“IN-sar”) are used to obtain image representations of this quantity called DEMs (“D-E-M’s”). Temperature gradients relative to this quantity (10[1])in dry and moist air parcels define the adiabatic lapse rate. (10[1])High values (-5[1])of latitude (10[1])and this quantity form the “tree line” of a habitat. Constant values of this quantity are represented (10[1])by contour lines on topographic maps. (-5[1])For 10 points, (10[1])what quantity is defined as zero at sea level? (10[1])■END■ (10[1])