Weather unipolar ground-based radar measurements can experience momentous changes by using other effective parameters that directly compromise the accuracy of the hydrometeorology applications. These radar measurements however, need to be calibrated for more accurate rainfall estimation. In addition to the radar-rainfall relationship (Z-R), this is a pragmatic approach based on careful analyses of other parameters include distance from radar, altitudes and rainfall time duration. This article introduces a new calibration approach using altitude parameters and time-stepwise processing of reflectivity-rainfall rate (Z-R) relationship. Based on previous work utilizing the radar-rainfall relationship; this article hypothesizes that the rainfall measurement from ground based radar are affected by other parameters. This Research leads to introduce a new effective parameter and generate two new empirical coefficients (a/b and c) in radar-rainfall relationship. Two consecutive years unipolar ground-based radar data sets with 190 occurrences of rainfall from 43 stations in calibration window of three hours; and the corresponding rainfall measured from registered rain gauges were used in this study. The results indicated that radar-rainfall relationship Z=AR^(b )is better improvised with altitudes effect (H) and empirical coefficient (c), such that Z=AR^(b ) H^(c ). The radar-rainfall relationship is denoted by R2min= 58, R2max=98; when altitude effect (H) is considered, the relationship is better improvised (R2min=71, R2max =98). It is, therefore, concluded that the use of other effective parameters (distance from radar, altitudes and rainfall time duration) leads to optimum accuracy of Z-R relationship. تفاصيل المقالة