A 27.75 MHz HF radar LERA MKIII system that consists of 16 Rx antennas in a linear array was installed at Taichung harbor at the western coast of Taiwan for monitoring surface wave and currents. Meanwhile, 8 km north-east of the LERA station is a long-range CODAR system, which is one among the 19 stations in the network around Taiwan Island that was setup and operated by Taiwan Ocean Research Institute. In the present study, data observed by the LERA and CODAR systems are analyzed using Barrick's theory and intercompared with in-situ measurements. About 40 days of simultaneous observations are used to assess the uncertainty of significant wave heights estimated using radar sea-echo from both systems under various sea-states. The error indexes are discussed with respect to the sea-states, Bragg frequencies and radar parameters of the two systems. The comparisons of the wave height evolution that obtained using single station demonstrates the potential of LERA system as a cost-effective tool for real-time monitoring of ocean wave field mapping.