Cartographic Information Analysis: a Case Study as an aid to teaching
R. Sudarshana, S. Sebastian*, and S. K. Bhan
Indian Institute of Remote Sensing, 4, Kalidas Road,
Dehradun - 248 001, India
*Society of Management Science and Applied Cybernetics.
C/o International Management Institute
B10/30-31, Qutab Institutional Area, New Delhi -110016, INDIA.
Abstract
A digital Evevation Model (DEM) was created for a small geographic area on the personal computer subsequent to
digitising the elevation from a map of 1:1000 image scale.
The DEM was transformed into a rester of single band image. and
several overlays of utilities and features were created as boundary files to be covered on the DEM. Several combination of the overlay considerations have been analysed and presented. In addition, case was taken to manage the data files in a way that suits the needs of imparting training in Geographic Information System (GIS). Several tutorial schedules that could be adopted for teaching are suggested and it is hoped that the emulation of this example would came a long way in the transfer of a technology which is fast emerging and is calling for attention.
Introduction
Development of spatial resources require an in-depth analysis of the existing units within a definitive geographic boundary in terms of location, quality and quantity. Further, the interrelationships of these units in providing useful solutions to the problems of space and resource use are of immense importance in explains the optimal behavior of geographic features. In the conventional scientific education, this situation is simulated by studying various academic disciplines initially and considering a multidisciplinary condition at the decision making level. But in the recent time technology has enabled us to consider the features as segregated layers of information which may be computed in various ways to indicate natural processes. The later ability is termed popularly as geographic information systems (GIS) suggesting an arrangement of systems analysis of various information, processing compatible geography.
Hence, the term geographic information analysis' broadly includes the capability of compiling, formatting, storing, manipulating and retrieving information of defined geographic enclosures for the benefit t of optional development of spatial resources. In the present context too, it has been envisaged to collect and collate diverse information in the ambit of their geography.
Moreover, realising the need of evolving case studies as an aid in teaching, the example has been organised into a set of modules of information and suggestions on how to develop curricular schedules around them are provide .The case study has already been adopted as a teaching aid and is found to be of interest amongst scientific workers.
Data Synthesis and Analysis Features of Study Area :
The study was conducted for the campus of Indian Institute
of Remote Sensing (IIRS), Dehradun which covers an area of about 20.9 acres. This small parcel of land is a segregated geographic entity in the sense that most of it forms a plateau which is surrounded by sharp slopes and deep valleys on three sides. Out of the 20.9 acres, nearly half lies on slope and valleys for the purpose of study, same portions of surrounding area were also included and the total range of altitude in the area was from 665.5 m to 699.5 m above chart Datum.
Compilation of Basic Data and Generation of Digital Elevation Model (DEM)
Basic source of data was the recently prepared map of campus region in the scale of 1:1000. A close grid was overlaid on the map and 982 points were sampled from grid intersections for elevation data. This intense sampling at very close interval provided a very real representation of the terrain of the region. The X, Y (map co-ordinates) and Z (elevation) data from all the 982 points were arranged in a LOTUS-spread sheet format and further subjected to interpolation on a personal computer using the following model.
where,
Z = elevation in meters
X = points at which surface is to be interpolate j
d= distance from the reference point to the point to be interpolated.
The above model follows the logic of weighted moving average or inverse squared distance weighting (Burrough, 1990) based on the argument that observations located close together tend to be more alike than observations spaced further apart. For the interpolation, a size of 250 (x) and 210 (y) was considered with a search radius of 20.6155281 and 10 nearest plaints. The inherent cell size was 0.177 meters in both x and y directions. The resultant grid raster was of the size of 52,500 elements and it seemed as the DEM for IIRS campus region. A contour plot of this DEM is shown as Fig. 1 and a perspective surface plot is given as Fig. 2.
Image Generation from DEM
The grid raster of interpolated DEM was reorganised and formated into a raster image of 210 lines and 250 columns. The image became akin to a single band satellite image and was provided with a header information on cell size, latitude centre, projection etc. enabling it to accept polygon overlays later. This DEM image was monitored on Image Display Analysis (IDA), (FEWS, 1989) on a personal computer. The image header details are provided in Table 1, while the image of DEM is shown in Fig. 3.
Table 1 : Header Information of DTM image
| Title: Image of The DTM of Indian Institute of Remote Sensing
|
| Image type code |
0 |
Generic |
| Projection |
3 |
Platee Carre |
| Height |
210 |
|
| Width |
250 |
| Lat-center |
19.50000 |
| Long-center |
26.00000 |
| X-center |
125.00000 |
| V-center |
105.00000 |
| DX |
0.1760000000 |
| DY |
0.1761904762 |
