The scientific and technological advances of the past two decades have led to significant enhancements in understanding and modeling of hydrologic processes as well as in understanding and improvements of quantitative forecasting of precipitation. Emplacement of WSR-88D radar network and the development of automated algorithms and the deployment of a dual-polarization WSR-88D test bed are examples. The uncertainty of hydrologic predictions is closely related to the uncertainty of the inputs of which precipitation is the most important. Simulation studies demonstrate that radar range and orientation have significant influence on the accuracy of the radar-estimated precipitation. However, data-based studies are needed to quantify the uncertainty of radar-rainfall estimates. During a special Field experiment (PRECIP98), The NCAR S-Pol radar was placed 26 km south-southwest of the WSR-88D at Melbourne, Florida (KMLB). PRECIP98 coincided with a TRMM experiment (TELFUN-B) in which high quality radar (KMLB) and rain gauge data were collected. The S-Pol has higher spatial and temporal resolutions than the KMLB. This unique high quality data set from the two radar systems and rain gauges was used to conduct comprehensive comparison between the two radar systems. Instantaneous reflectivity fields estimated by both radars were compared for different storms and the impacts of several factors such as radar orientation, bin size, and radar range were examined. Instantaneous and storm accumulated precipitation estimates were also compared at different spatial and temporal scales. Radar-rainfall estimates from both systems were also compared to rain gauge observations at different spatial and temporal scales. Issues such as accuracy of interpolation, grid size and shape, grid orientation, and distance from the radar were emphasized. Moreover, the S-Pol has higher spatial and temporal resolutions than the KMLB. The effects of higher spatial and temporal resolution on radar-rain gauge comparisons were also investigated.