Title :
A space marching inversion algorithm for pulsed borehole radar in the time-domain
Author :
Zhang, Yongmin ; Liu, Ce
Author_Institution :
Dept. of Electr. Eng., Houston Univ., TX, USA
fDate :
5/1/1995 12:00:00 AM
Abstract :
An iterative algorithm is developed to reconstruct the image of formation conductivity surrounding a borehole using time-domain data. The forward modeling employed in the algorithm is derived from the transmission line matrix (TLM) method, which is used to simulate electromagnetic waves propagating in formations with two-dimensional variations in cylindrical coordinates. A new structure of a transmission line mode is used to simulate a coil-type transmitter antenna in a borehole. Since the inversion algorithm proceeds iteratively and the part of the formation involved in the inversion marches in space step by step, no optimization is necessary, and problems caused by optimization procedure such as inverting large-scale matrix and computation of Jacobian matrix numerically, are avoided. This method is especially useful in cases where the analytic gradient is not available. The inversion algorithm is tested in formations having both one- and two-dimensional conductivity variations with coil-type transmitters. Investigation depth and resolution for noise-free cases are also discussed
Keywords :
geophysical prospecting; geophysical signal processing; geophysical techniques; inverse problems; radar applications; radar detection; radar imaging; radar signal processing; terrestrial electricity; EM method; borehole; buried object detection; coil-type transmitter antenna; cylindrical coordinates; electromagnetic wave; formation electrical conductivity; forward modeling; geoelectric; geology; geophysical measurement technique; ground penetrating radar; image; inverse problem; iterative algorithm; prospecting; pulsed borehole radar; space marching inversion algorithm; terrestrial electricity; time-domain; transmission line matrix; two-dimensional variations; Conductivity; Electromagnetic modeling; Image reconstruction; Iterative algorithms; Jacobian matrices; Radar imaging; Spaceborne radar; Time domain analysis; Transmission line matrix methods; Transmitters;
Journal_Title :
Geoscience and Remote Sensing, IEEE Transactions on