Fusion of stereo-optical and interferometric SAR DEMs | |
| Author | Karkee, Manoj |
| Call Number | AIT Thesis no.RS-05-02 |
| Subject(s) | Remote sensing Interferometry Optical measurements Topographic maps |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Spaceborne remote sensing is being used widely for decades to generate Digital Elevation Models (DEMs). Synthetic Aperture Radar Interferometry (InSAR) and Optical Stereoscopy are the two major satellite techniques of the topographic measurement. Both of these methods of generating DEMs have their own limitations. InSAR suffers from layovers, shadows and temporal decorrelations whereas image matching in stereoscopy suffers from cloud cover, radiometric variation and low-texture. These inherent problems cause voids and interpolated data in final product. This thesis presents a way of assessing accuracy and error phenomenon of both InSAR and Stereo-optical DEMs. Error statistics, error histogram and image profiles has been computed and compared with the reference DEM parameters. It was found that the overall quality of InSAR DEM is better than the Stereo-optical DEM. Moreover, InSAR DEM gives generally a bit higher elevation than reference DEM whereas stereo-optical DEM gives quite lower elevation. All of these assessments were carried out with SRTM and ASTER DEMs, former an InSAR product and later an optical product and for a test site of ～60 KM2 located in Central region of Nepal having fairly complex topography. This thesis finally presents an approach of DEM fusion to improve the overall quality and applicability of satellite DEMs. Algorithm starts with filling voids in the DEMs by taking slopes and aspects from another DEM and using elevation of surrounding pixels to calculate the absolute elevation of void pixels. In the next step, higher frequency components of optical DEM and lower frequency components of InSAR DEMs are filtered out, as they are more erroneous respectively. Filtered DEMs are then added to generate fused DEM. The accuracy of resulting DEMs was assessed in terms of error map and error statistics. Fused DEM shows up to 45% improvement in accuracy measures. Thesis has also addressed the way of modeling systematic error in the fused DEM and handling ASTER relative DEM. The approach is promising to improve the accuracy and completeness meanwhile maintaining the resolution to the best of participating DEMs. |
| Year | 2005 |
| Type | Thesis |
| School | School of Advanced Technologies (SAT) |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Remote Sensing (RS) |
| Chairperson(s) | Kusanagi, Michiro; |
| Examination Committee(s) | Borne, Frederic ;Souris, Marc; |
| Scholarship Donor(s) | Government of Japan; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2005 |