Analysis of interferometric SAR for topographic mapping

This thesis studies the estimation of terrain elevations using interferometry synthetic aperture radar (InSAR). The procedure uses the difference of phase measurements of the received radar signals at two antennas separated slightly in the cross-track direction, to determine the elevations more accurately than stereo SAR mapping, which uses SAR intensity images. The SAR phases are more sensitive to terrain elevation variations than SAR intensities. It is also possible to perform the same measurements with only one antenna by deriving two images of the scene on two separate passes (repeat-pass interferometry). An interferometric image (interferogram) is formed by multiplying pixels from the reference image with the complex conjugate magnitudes of pixels from the second registered image. This thesis reviews the basic principles of SAR imaging. These are followed by a discussion of principles of InSAR and its application. The stages in the processing to determine height information using InSAR are also addressed. The parameters which affect the accuracy of elevations determined by InSAR are then discussed, including the correlation of pixels of corresponding areas on two images, and the effects of different parameters on the correlation. The mathematical expressions needed to calculate the height error budget are presented. A model is developed to calculate absolute terrain elevations incorporating ground control data. The computation procedure is based on stereo radargrammetric mapping of overlapping SAR images, incorporating expressions for elevations based on the fringe information in InSAR. The model develops a simultaneous least squares adjustment of all the measurements by radargrammetry and interferometric SAR, together with ground control, using condition and observation equations. In this case the basic measurements include range, unwrapped phase, and the ground coordinates of control points. The purpose of the least squares adjustment is to determine the most probable solution for the ground coordinates of points identified in the image. The algorithm has been tested with a pair of ERS-1 and ERS-2 images in tandem mode over Sydney. The algorithm shows good performance in achieving SAR elevation mapping, as compared with contours on an orthophoto map. Moreover, the model simultaneously, determined planimetry positions of the points. The errors are highly affected by quality of the phase correlation of the points, since it was observed that there is a very high correlation between the position and height accuracy and the level of the phase coherency.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

1999

Author dc:creator

• Mirbagheri, Majid

• Topographic maps
• Synthetic aperture radar
• Interferometers

Statement dc:rights

• open access
• CC BY-NC-ND 3.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by-nc-nd/3.0/au/

Language dc:language

EN

Identifier

https://doi.org/10.26190/unsworks/4764

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/56022