30
kind of degradation. But according to latest estimation,
the area under degraded land has been reported as 107
million hectares (DAC, 1994). So far no effort has been
made by any single organisation to map land
degradation although estimates on the area of land
degradation are made by different agencies in the
country (Table 3). At National Remote Sensing Agency
(NRSA) the salt affected soil maps of the country at
1:250,000 scale are prepared in association with
National Bureau of Soil Survey and Land Use Planning
(NBSS & LUP), All India Soil and Land Use Survey
(A1S & LUS) and state government agencies of the
concerned states. The salt-affected soils are also being
mapped at 1:50,000 scale on a limited extent using
satellite data. The soil degradation map of India at 1:4.4
million scale prepared following GLASOD methodology
was published by NBSS & LUP. AIS & LUS has
initiated land degradation mapping using remote sensing
techniques at 1:50,000 scale during 1993-94 under the
scheme of “Application of Remote Sensing for soil
survey and land use planning”.
STATE OF THE ART : REMOTE SENSING
TECHNOLOGY FOR SOIL AND LAND
DEGRADATION MAPPING
Though conventional soil surveys were providing
information on soils they are subjective, time consuming
and laborious. Remote sensing techniques have
significantly contributed speeding up conventional soil
survey programmes. In conventional approach
approximately 80% of total work requires extensive field
traverses in identification of soil types and mapping their
boundaries and 20% in studying soil profiles,
topographical features and for other works. In the case
of soil surveys with aerial photographs or satellite data
considerable field work with respect to locating soil
types and boundaries is reduced and limited field
observations are needed to be made. Remote sensing
techniques have reduced field work to a considerable
extent and soil boundaries are more precisely delineated
than in conventional methods. Table 4 shows a
comparative analysis of soil resources mapping at
1:50,000 scale through remote sensing and conventional
approaches.
Application of remote sensing data from satellites
for soil studies began with the launch of Landsat-1 in
1972. Initially, the satellite data both in image and
digital formats are utilised for preparing small scale soil
resource maps showing soil subgroups and their
association (Mirajkar and Srinivasan, 1975; NRSA
1976, 1978, 1979 and 1981). In subsequent years,
remote sensing applications for the study on soils and
land degradation have increased. Survey of literature
reveals that remote sensing data from Landsat MSS were
used for mapping soils (Venkatratnam, 1984; NRSA and
AIS & LUS 1986); and degraded lands like eroded lands
Table 1. Soil Resources Mapping - Levels of Intensity, Classification.
SI.
No.
Type/Level of
Survey
Basic
Mapping
Unit (ha)
Scale of
mapping
Mapping Base
Level of mapping
Level of planning
operation
1.
National Level
2500
1:1,000,000
Satellite imagery/
Toposheets
Associations of great
groups
National Level
planning, IGBP
2.
State Level
160
1:250,000
Satellite imagery/
Toposheets
Association of sub
group/families
State/regional level
planning
3.
Reconnaissance
5.0-10.0
1:50,000
Satellite imagery/Aerial
photos/Toposheets
Associations of series
Macro-level district/
sub-catchment
4.
Semi-detailed
1.0-1.5
1:20,000/
25,000
Satellite imagery/Aerial
photos/Toposheets
Association of series
Macro-level district/
taluk/watersheds
5.
Detailed
0.25-0.5
1:4,000/
15,000
Satellite imagery/
Cadastral maps/aerial
photographs
Series and phases
Macro-level village/
sub-watersheds
6.
Project
execution
0.01-0.10
1:2,000/
4,000
Enlarged cadastral maps
or plane table maps
Phases of series
Micro-level/farm level
