Data Used
Two types of data have been used in this study, i.e. satellite and field data. Satellite data of IRS-IB, LISS-II (linear image self-scanning spectrometer) in all four bands (B1: 0.04-0.52um, B2: 0.52-0.59um, B3: 0.62-0.68um and B4: 0.77-0.86um) are used for three time periods of year1993. Three different months have been chosen for the satellite data because of considerable variation in salinity as well as in vegetation cover. Topographic maps of survey of Pakistan used in the study were 44 E/3, 44 E/7, 44 E/8 and 44 /16 of scale 1:50,000. Layout maps of irrigation canal and surface drains were also used. The watertable data for more than 150 Piezometer locations (Figure. 2) lies within the S-1 area were used to know the status of soils under waterlogging risk. ILWIS 2.2 for Windows system has been used for all remote sensing and GIS analysis. Information about water and soil quality, soil types, agricultural practices, crop yield, irrigation facilities and necessary ground truth data of the study area will be obtained and used in the remaining part of the study.
The IRS
LISS-II digital data were registered to Survey of
Pakistan topographical sheets using an
image-to-map registration algorithm (UTM map
projection with 36.25m ground resolution). About
30 common, well identified and uniformly
distributed GCP points were selected from both,
the displayed image and topographical sheets. The
image was then registered using affine
transformation method and the nearest
interpolation was used for arrangements of the
coordinates of each picture element. The average
error was within one picture element in terms of
precision after the geometric correction.
Following this procedure, the others scenes were
registered through image-to-image tie-down
algorithm using ILWIS 2.2 for windows. False color
composite (FCC) image was generated using band
combination of R:G:B = 4:3:2 for better and visual
interpretation of salt-affected lands in contrast
to other features (Figure 3).
