In this chapter, we take a closer look at the possible errors in identifying wave loads on a circular cylinder, based on measured wave elevation data and interpreted through linear wave theory. Both theoretical analyses and experimental tests are carried out. Since the accuracy of identified results is directly dependent on the collected data of wave elevation, some unexpected errors may be injected into the results if the data is not informative enough. To begin with, we present a mathematical analysis in which wave gauges are placed evenly around the cylinder, with different setups using three, five, seven, and nine gauges. From this, error functions are developed to describe how both the number and the distribution of gauges affect the results. We then move on to experiments to verify the theory. Interestingly, the amplitude and phase errors obtained from experiments with only three gauges can be well explained by the theoretical model. Building on this, we introduce an improved method tailored for the three-gauge setup, which proves to work effectively in certain cases when tested with real data. Finally, we provide a broader discussion comparing two different ways of processing the identified wave loads, highlighting their differences and implications.