Collection of data and preparation of maps
The first step in a GIS project is to create a database of spatial, non-spatial and attribute information.
In this study data acquired by Indian Remote Sensing satellite IRS-1C, LISS-III has been used as a primary data source for carrying out rapid reconnaissance survey. The false colour composites (FCCs) in the form of geocoded data on 1:50,000 scales have been used to generate land use/land cover map of the region. The interpretation was substantiated by IRS-1C, PAN image through carrying out field surveys for ground trusting. Apart from these data census data and Delhi Statistical Handbook (1998) were also used for a number of auxiliary information. The methodology adopted to generate the land use/land cover map is depicted in figure 1.
Data products used for the study
Table 2: Satellite data used for the study
| Satellite |
Sensor |
Scale |
Spatial resolution |
Path/row |
| IRS-1C (1999) |
PAN (Panchromatic) |
1:25,000 |
5.8 m |
56/60 |
| RS-1C (1999) |
LISS-III |
1:50,000 |
23.6 m |
56/60 |
Table 3: Ancillary data used for the study
| Toposheet |
Year of publication |
Scale |
Source |
| 53 H/1 |
1977 |
1:50,000 |
Survey of India |
| 53 H/2 |
1977 |
1:50,000 |
Survey of India |
| 53 H/3 |
1977 |
1:50,000 |
Survey of India |
| 53 H/6 |
1977 |
1:50,000 |
Survey of India |
| 53 H/7 |
1977 |
1:50,000 |
Survey of India |
| 53 D/13 |
1977 |
1:50,000 |
Survey of India |
| 53 D/14 |
1977 |
1:50,000 |
Survey of India |
Preparation of Thematic Maps
Thematic maps on land use/land cover were prepared based on the interpreted data using LISS III FCC, PAN, SOI toposheets and the field survey. Visual interpretation and digital analysis of satellite imagery were performed to delineate various land features.
Digitisation of Maps and Spatial Data Automation
The various thematic maps of 1:5000 scale were scanned and a raster to vector conversion was carried out. Each feature of the point, line and polygon digitised was labelled, as defined in the data dictionary. These labels were used as identifiers to link the attribute data of each feature. The digitised thematic maps then were imported to ARC/INFO as coverages. After executing 'clean' command for topology creation, the dangle node errors were removed interactively in ARCEDIT module. After all offshoot/undershoot errors have been removed, Feature Attribute Table (FAT) was created using 'build' in ARC prompt. Then each land use/land cover category was assigned a code and these codes were attached to appropriate records of FAT interactively. A Look-up-Table (LUT) was also created to assign a shade symbol for each land use/land cover category. Attribute codes for different categories were verified and additional attributes added into the features database. The theme coverage was made ready for updating into map library and also for analysis.