The purpose of the study is to evaluate the accuracy of the retracked TOPEX/Poseidon (T/P) 10-Hz and Jason-2 20-Hz altimetry sea surface heights (SSHs) around Taiwan by comparing to Anping tide gauge records. The sea state and bathymetry in the study area are highly various. Taiwan Strait located at the west of Taiwan has an average bathymetry less than 200 m and its amplitudes of ocean tides are extremely high. In contrast, the western Pacific Ocean located at the east of Taiwan has deep bathymetry of 4000m and relatively low amplitudes of ocean tides. The measurements of radar altimeters are inaccurate in shallow oceans especially near the coastlines because the displacement of the midpoints of leading edges results from the waveforms returning from ocean-land areas. This disadvantage can be effectively overcome by waveform retracking technique. In this study, retracking algorithms including the Offset Center of Gravity, threshold, modified threshold, and ice retrackers were used and the performance of different algorithms were examined by computing the improvement percentages (IMPs). The result shows that T/P and Jason-2 data can be significantly improved by the waveform retracking with the highest IMP at 82% and the optimal retracking algorithm highly depends on the characteristics of the study area. In addition, the retracked Jason-2 SSHs agree better with Anping tide gauge records than non-retracked data.

The global navigation satellite systems have been applicable. But in the process of positioning, there are many errors which affect the accuracy of positioning. In a relative position case, many errors of two receivers are similar such as receiver clock, satellite clock and satellite orbit biases. The ionosphere and troposphere delays are also similar if the length of base line is short. Therefore they can be eliminated by a double difference technique.But the longer the baseline is, the more different the ionosphere and troposphere delays will be. The former could be eliminate by linear combination. The latter must estimated by models.This research included several reference stations and determined the relative tropospheric zenith delays between the master and subsidiary reference stations. Then the relative tropospheric zenith delay between the rover station and master reference station was estimated by an interpolation technique. The accuracy of positioning would be improved through the interpolated estimation.

Due to the application of cyber city are getting more and more, the generation of a photo-realistic cyber city is becoming an important research topic. Conventionally, the pictures taken on the ground or by vertical aerial imaging will introduce serious occlusion effect and geometric distortion, thus will degrade the visual effect of a photo-realistic city model. In this paper, we thus propose an automatic scheme for facade texture mapping according to a mechanism for the selection of better imaging geometry for the purpose of reducing human interference and increasing the texture quality. In the research, the occlusion problem is solved by means of a vector-based occlusion detection algorithm. In case of occlusion, it will be removed and restored from the other images taken from other viewing positions. Experimental results demonstrate that the proposed scheme can automatically generate the facade texture information when occlusion effect occurred. The texture quality can satisfy most of the cyber city application as well.

Three dimensional geographic information systems describe the reality with environmental elements such as buildings, roads, vegetation etc. Among those elements, building is the most prominent. Aerial images are commonly used in building reconstruction. In building reconstruction with aerial images, building detection, image matching and building modeling are the three major works. This study uses multiple strips acquired from highly overlapped aerial images to perform 3D building modeling. Multiple image matching and building modeling are the major works in this study. Test cases include different types of building roofs. We first select the working area in the master image to extract building features. Then, the detection of building information with line features can aid the image matching. Multiple image matching employs multi-windows with multi-epipolar constraint to find conjugate positions in the same procedure. In the generation of line segments, line tracing is performed in the image space with 3D information. Building modeling is made by the integration building boundaries and roof surface information. The results show that multiple images matching can improve the matching accuracy. Model refinement with 3D roof point clouds can work well. Compared with reference data, the RMSE of building model in most of case can be smaller than 0.4m.

Thermal infrared data is important when conducting remote sensing investigation, for it could be acquired both in day and night. The change of temperature has characteristic significance of representation. So the thermal infrared images are used not only in the domain of surveying, but also in the environment monitoring, the urban development, and the disaster prevention. Before interpreting the remote sensing data, one would make sure that each image of bands has similar image geometry. Calibrating such geometry could prove that the effect from the lens distortion had been minimized. In such case, calibrated thermal images are necessary to guarantee that the image coordinates can be registered to the image coordinates of the other bands. A thermal sensor, FLIR-T360 has been calibrated in this research. Two aspects of calibration executed are geometric and radiometric. A conventional calibrated template has been improved for using in the geometric calibration. The thermal sensor’s interior orientation elements were then found by using a field method. In the radiometric aspect, in situ method has been employed to determine temperatures of the chosen control points. The results of correction in geometric and radiometric aspect are also shown and discussed in this study.