DEM GENERATION OF JHARIA COAL FIELD AREA USING

SAR INTERFEROMETRYManoj Joseph

Daniel SalvadorK.Hareef Baba ShaebDr.Hitendra Padalia

Dr. S. Rama Subramoniam

Guide : Dr. R.S. Chatterjee

Contents

• Objectives• Interferometric SAR• Procedure• Data• DEM• Analysis• References

1. Objectives

• To generate DEM for Jharia coal field area (Jharkhand) using SAR data

• To compare the results with SRTM• To analyze the coherence map of the study

area.

2. Interferometric SAR

• The basic techniques for extracting height from SAR images

• Phase difference between the two SAR images is used to generate Digital Elevation Model (DEM).

2. Interferometric SAR

Fig.1.Basic geometry of SAR interferometry

3. Procedure• Generation of DEM using SARDA

– Registration– Baseline estimation– fringe generation– Coherence estimation– Phase unwrapping– Phase to height

• Error Calculation using MATLAB– Read binary image– Resize data

• Analysis

4. Data

• Single Look Complex[2 bytes] + j[2 bytes]

• C band: 5.6 cm• DoP:12-4-1996 & 13-4-1996• Polarization : VV• Ground Resolution : 25 meter• Swath : 100 kilometer• Data collected in descending Node

4. Data - Work Area• Between latitude 24.20 to 24.53 E and longitude

85.65 to 86.09 W to the west of Jharia Coal field in Jharkhand.

• General altitude varies from 250 meter to 650 meter.• The broad categories of land use and land cover

types present in the study area are sal dominated forests (confined mainly to elevated areas), large chunk of wastelands, agriculture, waterbodies and settlements.

5. DEM – Registration

5. DEM – Estimated Baseline

From information available in the leader files of the master and slave images of the data pair.

5. DEM - GenerationFringe Estimated coherence

Smooth Fringes Unwrapped phase

5. DEM w.r.t. ellipsoidHeight

Slope

Height drapped with intensity data

6. Analysis - Error

6. Analysis - Considerations• For quality assessment, 28 points have to be used (20 interior

points and 8 boundary points), in order to be in the NDCDB – USGS standard

• Precise knowledge of the baseline geometry is needed because an error in the baseline cannot be distinguished from a slope on the terrain surface

• Resample in azimuth direction produces aliasing and loss of spatial resolution

• Due unavailability of GCPs, we could not compare out result for precise validation.

• DEM sensitive to:– Layover in ERS DEM caused by steep slopes– Loss of coherence of hilly slopes covered by forest

6. Analysis - Coherence

• Degree of complex correlation

Agriculture

Waterbody

Forests

Ravenous land

Fallow land

6. Analysis - Coherence• Order of coherence

cropped field>ravenous land>fallow land>dense forest>settlement >waterbody

• Forest area showed low coherence due to volume scattering and complex terrain.

• Water body showed low coherence due to temporal change and low singal to noise ratio (large errors in height surface generation)

• Agriculture: high coherence due to surface canopy. Ravenous land also have high coherence due to undulating topography.

7. References

• R.S. Chatterjee, Lecture Notes• R. Gens, Quality Assesment of SAR

Interferometric Data, ITC, The Netherlands, 1998.

• G. Franceschetti and R. Lanori, Synthetic Aperture Radar Processing, CRC Press LLC, 1999.

Thanks.