Practical Work In Geography Part I Chapter 6 Spatial Information Technology

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Data display

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Difficult network analysis

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Complex data structure

D.

Buffering

The hallmark of GIS is overlay operation. An integration of multiple layers of maps using overlay operations is an important analysis function. In other words GIS makes it possible to overlay two or more thematic layers of maps of the same area to obtain a new map layer. Map overlay can be used to study the changes in land use over two different periods.

The following advantages of a GIS are worth-mentioning:

1. Users can interrogate spatial features displayed and retrieve associated attribute information for display and analysis.

2. Maps can be drawn by querying or analysing attribute data.

3. Spatial operations can be applied on integrated data base to generate new sets of informations.

4. Different items of attribute data can be associated with one another through shared locations code.

The important components of GIS are as under:

1. Hardware, 2. Software, 3. Data, 4. People.

1. Spatial data input

2. Entering of the attribute data

3. Data verification and editing

4. Spatial and attribute data linkages

5. Spatial analysis.

The spatial information technology relates to the use of technological inputs in collecting, storing, displaying, retrieving, manipulating, managing and analysing the spatial information.

Raster data represents a graphic feature as a pattern of grids of squares whereas Vector data represents the object as a set of lines drawn between specific points. Consider a line drawn diagonally on a piece of paper. A Raster file would represent this imagery subdividing the paper into a matrix of small rectangles similar to a sheet of paper called cells. Each cell is assigned a position in the data file and given a value based on the attribute of that position. Its row and column coordinates may identify any individual pixel.

Fig: Generic Structure for a Grid

Fig: Effect of Grid Size on Data in Raster Format

Vector Format: A Vector representation of the same diagonal line would be record the position of the line by simply recording the coordinates of its starting and ending points. Each point would be expressed as two or three members depending on whether the representation was 2D or 3D often referred to as XY or XYZ co-ordinates.

Fig: The Vector Data Model is based around coordinates pairs.

The following sequences of the activities are involved in GIS related work:

1. Spatial data input: These could be summarised into the following two categories:

(a) Acquiring digital data site from a data supplies. The present day data supplies make the digital data readily available which range from small scale maps to the large scale maps.

(b) Creating digital data: Manual input of data to a GIS involves four main stages:

• Entering the spatial data.

• Entering the attribute data.

• Spatial and attribute data verification and editing.

The manual data input methods depend on whether the data base has a vector typology or grid cell structure.

2. Entering the attribute data: Attribute data defines the properties of a spatial entity that need to be handled in the GIS but which are not spatial.

3. Data verification and editing: The spatial data captured into a GIS require verification for the error identification and corrections so as to ensure the data accuracy.

4. Linkages: GIS typically links different data sets. Suppose we want to know the mortality rate due to malnutrition among children under ten years of age in any state, we must first combine or link the two. In one number of children of this age group and another contains the mortality rate from malnutrition.

GIS: Geographic information centre or GIS is a database or particular kind containing spatial information about various levels of observations. GIS can be considered as a tool to analyse resource and environmental information in a special context.

GIS is a powerful set of tools for collecting, storing, retrieving at will, transforming, displaying spatial data from the real world.

Types of GIS are as under:

(i) Vector or polygon and

(ii) Roster or grid structure.

Three basic elements of cartography are as under:

(i) Formalisation, (ii) Cognition and analysis, and (iii) Communication.

Computer helps in cartography in the following ways:

(i) Maps are made quickly.

(ii) Maps are made according to users needs.

(iii) Map construction is possible even if skilled cartographer is not available.

(iv) Map making has become less expensive.

(v) Maps can be made more attractive.

(vi) Map reproduction has become fast.

(vii) Updating of the map can be done if data are in digital form.

The following are the elements of data structure:

(i) Size of typology, (ii) Lightness or (grey) value, (iii) Grain or texture, (iv) Colour Hue, (v) Orientation, (vi) Shape.

Apple, Arc/Info, Auto CAD and Map Info and Gram.

GPS or Global Position System: It is all weather radio navigation system developed by US military in which individual receivers process data beamed down from satellites. lt provides three dimensional positions 24-hour-per-day a basis around the world.The space satellite system consists of 24 satellites in a circular orbit and with an orbital period of 12 hours. The orbits are inclined to the equator at 55 degree. The satellites carry an atomic clock moving and generating stable signals. These signals carry information about time and ephemeries of satellites. The ground receivers receive these transmitted signals to compute the position on the earth based on the satellite position. Most of the navigation systems use input from just one satellite receiver. This provides latitude, longitude and altitude on any spatial unit.

The space technology has changed mapping in many ways. Soft copy images have replaced printed maps for many applications. Automation is also changing the quality as well as variety of spatial information that can be mapped. Further, Geographic Information System (GIS) is expanding the role of spatial mapping and analysis in decision making. The development of modern data-gathering techniques and computer asserted cartography give new impetus to spatial data storage and exchange. Simultaneously, the combined use of Geographic Information System (GIS) and Digital Image Processing (DIP) provide better prospects of geographical monitoring and forecasting over wide areas within limited timespan.

GIS or Geographic Information System: It is a database of a particular kind containing spatial information about various levels of observations. GIS can be considered as a tool to analyse resource and environmental information in a spatial context.

GIS can be defined as, “A powerful set of tools for collecting, storing, retrieving at will, transforming and displaying spatial data from the real world.”

Geographical Information System (GIS) offers such capabilities as they integrate multi-sector, multi-level and multi-period data base. Subsequently, GIS can be used as decision support system, identifying and integrating, monitoring and predicting natural hazards which are the major environmental risks experienced in India. Integrated watershed management plans could help reduce the impact of disasters that continuously threaten Indians.

Land-use is an important input in the geographical monitoring of rural as well as urban resources of a region. The general land cover classification can be derived from past changes in land use in general and forest cover in particular. Forest maps of two time periods can provide information of forest cover changes Satellite, Remote sensing can be effectively used for land use mapping and for monitoring forest degradation process in the country.

Deforestation, for example, is a serious ecological problem in the Himalayas.

Vector GIS: Vector structure denotes spatial units of their features to be represented. Such units are of uniform size and shape and relative location within an area.

Roster GIS: In the Roster (image) data, spatial objects are made of contiguous cells sharing the same attribute within the regions. Attribute dimensions is described as set of grids in which the value assigned to each cell expresses its over all characteristics.

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V. Imp.

Resource management of a region is performed either by manual map overlay method or by computer technology using numerical special data sets or geo-based files. Only a few maps can be overlaid simultaneously for visual analysis by manual map overlay method. The computer-assisted approach requires information in digital form. In this approach inter-relation of resource features (attributes or factors) is performed through numerical transformation.

The development of modern data gathering techniques and computer assisted cartography give new impetus to spatial data storage and exchange. At the same time combined use of GIS and DIP (Digital Image Processing) provide better prospects of geographical monitoring and forecasting over wider areas within limited time span. It would be easy to develop predictive modelling capabilities for effective public policies in years to come.

Advantages of GIS:

(i) GIS provides an opportunity to interpret various geographical, topographic, socioeconomic spatial data in relation to spatial analysis and modelling.

(ii) Its main emphasis is on integration of conventional land based and remotely sensed data so as to develop comprehensive databases suitable for various levels of spatial planning.

(iii) It can play an effective role for decision support system of sustainable development and management of the natural resources which are a prime natural capital for human sustenance and development.

GIS has many practical applications. Important among them include:

1. Mapping (Cartography)

2. Data base management

3. Data queries based on

– Spatial/Location

– Attribute/Features

4. Spatial Modelling

– Capability, suitability analysis

– Sensitivity analysis

– Simulation.

Land-use suitability analysis helps in taking decision on different land related developments. The GIS analysis integrates various natural, anthropogenic and interactive factors to produce three types of maps.

(i) A map showing land use will cause the least change in environmental processes.

(ii) A map showing qualitative predictions of environmental impacts of proposed development. It also gives certain projects to be carried out and specific environmental actions to be controlled.

(iii) A map showing the best and least suitable locations for those actions.

The land use planning in marginal regions like Himalayan region, Rajasthan Desert requires such mapping. The analysis of land suitability for agriculture in highlands will produce information and maps related to soil erosion, slope, altitude, water availability and nutrient availability.

The U.S. Department of Agriculture Soil Conservation Service has develop the Land Evaluation and Site Assessment (LESA) system to determine the quality of land for agricultural uses and to assess agricultural land areas for their economic viability. India should also take up such projects.

Multi-criteria analysis has become popular for integrity, various GIS maps like soil, slope and accessibility are integrated by indicating their rulings and weightage in order to ascertain a final GIS product.

The following six basic types of graphic variables are popular:

(i) Size of Typology: Differences in size of the symbols and lines showing the spatial distribution pattern of a phenomenon without much clustering. The dots of different sizes represent different quality of an element.

(ii) Lightness or (grey) value: In this process the distribution of an element is shown by the variation in the intensity of grey colour. The lighter shades show lower densities and deeper or darker shades show higher densities.

(iii) Grain or Texture: The distribution of an element is shown by different shades to represent varying intensity or density. In this method black and white colours are mostly used.

(iv) Colour Hue: Hue refers to various colours we perceive: red, green, blue and combinations. This method makes use of different colours to make the distribution of various features distinct on map.

(v) Orientation: Difference in orientation refers to patterns and not to the line elements that form the base map.

(vi) Shape: Differences in shape can refer differences in the points, lines, and area patterns used as symbols. The various symbols are included for identifying shape differences.

Point, line and area.

Hardware, software, data, people.

Overlay.

Resolution.