Civil Insight: A Technical Magazine Volume 3 | Page 22

Chaudhary S. et al.
Civil Insight (2019) 21-28
2) Methodology
The following satellite data, as shown in Table 1, have been used in the study:
Table 1. Details of satellite data
Satellite Sensor
Landsat 8 Landsat OLI
Date of
Acquisition
December 15, 2017
Wavelength width in
μm/band
0.525-0.600, Green
0.630-0.680, Red
0.845-0.885, NIR
Spatial
Resolution
30m
2.1) Landsat 8
Landsat 8 is an American Earth observation satellite launched on February 11, 2013. It is the eighth satellite
in the Landsat program; the seventh to reach orbit successfully. Originally called the Landsat Data
Continuity Mission (LDCM), it is a collaboration between NASA and the United States Geological Survey
(USGS). NASA Goddard Space Flight Center in Greenbelt, Maryland, provided development, mission
systems engineering, and acquisition of the launch vehicle while the USGS provided for development of
the ground systems and will conduct ongoing mission operations (Wikipedia, 2019).
2.2) Software used
ArcGIS 10.6.1 (ArcGIS, 2018) software was used for satellite data processing and analysis.
2.3) Preliminary study
Roshi and Melamchi watersheds were studied from Google Earth. Some essential topographic sheets,
namely 278503 C and 278507 C were collected and studied.
2.4) Delineation of watershed and mosaic preparation
Digital Elevation Models (DEMs) of the project sites were acquired from the USGS site. The two DEMs
were joined to form a mosaic using mosaic tool in Arc Toolbox. The watershed was delineated using the
ArcGIS software separately for Roshi and Melamchi watersheds.
2.5) False Color Composite (FCC) of the study site
After delineation of watershed and study area, False Color Composite (FCC) of the study was generated
using band 5, 4, and 3. Further classification was carried out on this extracted scene to reduce space and
time consumption.
2.6) Classification
Visual Image Interpretation, a classification technique, was applied in the study. It is a process of identifying
what we see on the images, and it communicates the information obtained from these images to others for
evaluating their significance. The richness of the red in FCC image indicates the density of the vegetation.
Dense forests have appeared in dark red tone with rough texture, and the lighter red tone with smooth
texture represents open forests. Human settlements are sparsely distributed and only few polygons of
crowded settlements were identified on the map. During the process of supervised classification, on-screen
digitization was done in Arc Map 10.6.1 software. Spectral signatures of different ground features like
forest, agriculture area, barren land, shrub land, and built-up area were created by drawing a polygon on
the map. The classes were then assigned their respective attributes. Finally, the area statistics of different
categories of LULC and color-coded classified map of Melamchi and Roshi watersheds were generated.
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