Methods

This study mainly focuses on the Thar Desert area since the desert area is not covered by the vegetation and thus easier to get the surface information.To look at the subsurface features the radar data is a good option so in this study PALSAR and SIR-C data are used.

 

PALSAR

Phased Array type L-band Synthetic Aperture Radar (PALSAR) is an active microwave sensor using L-band (1.27 GHz) frequency with wavelength 0.2360571 m and polarization HH and HV. It can penetrate through clouds and look at night. PALSAR was one of the instruments on the Advanced Land Observing Satellite-1 (ALOS-1) which is the mission of the Japan Aerospace Exploration Agency (JAXA).

In process of PALSAR data, different filters, Lee, Enhanced Lee, Frost, Enhanced Frost, Gamma, Kuan, Local Sigma and Bit Errors are used intending to remove the speckle. Different polarization combination is also used to enhance the features.

 

SIR-C

Spaceborne Imaging Radar-C (SIR-C) has X-band, C-band and L-band and in this study C-band (5.298 GHz) and L-band (1.249GHz) are used with polarization HH, VV and HV and the product type is single-look complex which consists of one single-look file for each scene, per frequency.

SIR-C data can’t be opened directly with ENVI, it needs to be synthesized first and in this process samples, lines, range and azimuth in the header are needed. The synthesized data is processed with different filter and polarization combination as mentioned above.

For SIR-C data process, it is hard to remove the speckle and visualize anything in the image (Fig.2.) and I think maybe the way I synthesized the data is not right so I can’t get anything whatever I did in my later process.

 

 

 

 

 

 

 

 

 

 

 

 

 

SRTM 1 Arc-Second (30 m) Global

Shuttle Radar Topography Mission (SRTM) is to produce digital topographic data for the Earth's land surface, with data points located every 1 arc-second (30 m). The absolute vertical accuracy of the elevation data will be 16 meters.

SRTM is downloaded from USGS website is used to look at the topography.

 

Landsat

Landsat 8 images are used to map the surface features and are also from USGS website. 

With Landsat data the main processes is decorrelation stretch and custom stretch to enhance the visualization. Decorrelation stretch is to remove the high correlation in different band and generate more colorful image in three bands while multispectral data generates smoother image. With this it is easier to visualize different features in the image. SPEAR Independent Components Analysis is also tried to improve the visulization which transform the input bands into the linear combination but it doen't works as well as Decorrelation Stretch.