Satellite altimetry for hydrological purpose

Abstract

As a new spatial measuring technic developed in 1970s, altimetry was designed to determine the sea surface height based on spatial technology, electronic technology and microwave technology. It also plays an important role in geodesy and oceanography; meanwhile, it can provide all-weather and repetitious measurements in global region for the studying of variation of SSH, earth gravity field, ocean circulation as well as submarine topography. In addition, real-time data can also be provided for the field of weather forecast, ocean circulation forecast and wave forecast in globally. Satellite radar altimetry, well known as TOPEX/POSEIDON, JASON, ENVISAT, which have been originally designed to measure global ocean surface height, nowadays, also demonstrated with great potential for applications of inland water body studies. Therefore, the main task of this study is to analyze and summarize the relevant theory and technology of altimetry waveform, waveform retracking methods based on the investigative research up to now. And above all, data used in this study is Topex geophysical data and sensor data from 1992 until 2002 provided by NASA (http://podaac.jpl.nasa.gov/). The main content of this study are listed as follows: - Discuss the theory and process of altimeter waveform, and distinguish the real waveforms from ideal ones. - Waveform classification based on different shapes. - Automatic waveform filter is designed to move out noisy data. - The most popular retracking methods (OCOG, Threshold, 5β) are compared and evaluated with respect to different groups of waveform. And finally an optimal Lake level height is to be generated by sufficient combing all the above retracking methods. - Generate time series of Lake level height (from 10Hz data) in selected water bodies; evaluate the result by comparison with in-situ gauge data.