Practical Work In Geography Part I Chapter 4 Use Of Computer In Data Processing And Mapping

C.

Pie diagram

A.

Points

D.

x

A.

construct graphs

A computer is a fast and versatile machine that can perform simple arithmetic operations such as addition, subtraction, multiplication and division and can also solve mathematical formulae. It can be used for data processing, preparation of diagrams, graphs and maps, etc.

Computer saves time and improve efficiency in data processing and graphical presentation. Computer is more versatile as it facilitiates the on screen editing the text copy and move it from one place to another or even delete the unwanted text.

2. It can handle huge volume of the data.

3. It further enables validation, checking and correction.

(iii) The types of graph or map headings and other formats can be changed easily.

MS Excel is also called Spread-sheet. It is the work-sheet. The spread-sheets are located in workbooks or excel files. Excel worksheet contains 16384 rows and 256 columns.

Spatial data : The spatial data represent a geographical space. They are characterised by the points, lines and the polygons. The point data represents positional characterstics of the some of the geographical features such as schools, hospitals, wells, villages, towns, etc. on the map.

Non-spatial data: The data describing the spatial data is called as non-spatial or attribute data. For example, if you have a map showing positional location of your school you can attach the information as the name of the school, number of students in each the class, available facilities like library labs, etc. In other words, you will be defining the attributes of the spatial data. Thus non-spatial data are also known as attribute data.

The geographical datas are available in analogue or digital form.

Use of Computer (Practical Work in Geography)

The mapping software: mapping software provides functions for spatial and attribute data input through on screen digitation of scanned maps.

A digitised map consists of three files. The extention of these files are shp, shx and def. The def file is dbase file that contains attributes data and is linked to shx and shp files.

Do yourself.

Do yourself.

A computer is a general purpose machine that processes data according to a set of instructions that are stored internally either temporarily or permanently.

Computers are of the following types:

(i) P.C (ii) Macintosh

(iii) Laptop (iv) Super Computer

(v) Hand Held Computer.

Hardware units of a computer are as follows:

(i) Central Processing Unit (CPU).

(ii) Visual Display Unit (VDU).

(iii) Input/Output devices.

(iv) Storage devices.

In its most general form, software refers to all the programs, which can be used on a particular computer system. More specifically, software means all those programs, which can in some way assist, all users of a particular type of computer to make the best use of their machine. Software governs the operation of a computer system and makes the hardwares run. Software is classified as:

(i) Applications Software and

(ii) Systems Software.

(i) Data capture or data acquisition:

(ii) Geo-coding of Geo-referencing of Raster Image.

(iii) Digital fair mapping and

(iv) Map reproduction.

A computer consists of a number of store devices which are:

(i) Hard Disk (ii) Floppy (iii)Tape (iv) Magneto Optical Disk (v) Compact Disk (CD) (vi) Cartridge These devices vary in their capacity of data storage, from megabytes (MB) to gigabits (G.B). Q. 7. What is an operating system? Ans. Operating System (OS) is a set of programs that contain instructions for coordinating all the activities among computer

hardware resources. For example, the operating system recognises input from an input device such as the keyboard, mouse, microphone, or P.C Camera coordinates the display of output on the monitor, instructs a printer how and when to print information, and manages data and instructions in memory and information stored on disk.

Popular types of operating system include DOS (Disk Operating System), UNIX and its variants, VMS (Virtual Memory System), Microsoft Windows, etc.

Central Processing Unit (CPU): It is the nerve centre of any digital computer system. It coordinates and controls the activities of all other units and preforms all the arithmetical and logical process to be applied to the data. CPU has three separate hardware sections — (i) internal memory (ii) arithmetic unit and (iii) a control section. Chip (a thin silicon wafer containing a large amount of integrated electronic circuitary) is the building block of a computer and performs various functions e.g. doing arithmetic operations, serving as the computer’s memory or controlling other chips.

The Control Unit: The role of control unit is quite similar to a traffic cop. It interprets each instructions issued by a program and then initiates the appropriate action to carry out the instructions.

The Arithmetic Unit (ALU): It performs arithmetic comparison and logical operation. Arithmetic operations include addition, subtraction, multiplication and division. Comparison operations involve comparing one data item to another to determine if the first item greater than, equal to or less than the other item.

Logical operations use conditions alongwith logical operations such as AND, OR and NOT. For example, if only non-salaried employee can receive overtime pay, the ALU must verify that the employee is non-salaried AND worked more than 30 hours before computing an overtime wage.

Memory : During processing the instructions to be executed as well as the data required by those instructions are placed into memory by the processor. The memory is a temporary storage place for data instructions and informations.

RAM (Random Access Memory) : Memory into which data can be written and from which data can be read. It consists of memory chips that can be read from and written by the processor and other devices. When the power is switched on to start a computer, certain operating system files load from a storage device such as a hard disk into RAM. These files remain in RAM as long as the computer is running. Additional programs and data are also loaded into RAM from storage. The processor interprets the data while it is in RAM. The program with which you are working is usually displayed on the computer screen. Most RAM is volatile. It loses its contents when power is switched off.

ROM (Read Only Memory) : It refers to memory chips storing data that only can be read. The data on ROM chips cannot be modified hence the name read only. It is non-volatile. Its contents are not lost when power is removed from the computer. Memory containing information which is present and permanent and which cannot be written but can only be read by program routines.

Digital Mapping : Geo-coded raster image is used as a backdrop to draw point, features, live features and aerial features and

annotate them with proper symbols and texts. Alternatively, the above features or the raster image may simply be digitized without using symbols to create cartographic database. The digital map may be subjected to automated cartographic process, like generalisation, classification, etc.

A computer system consists of two basic components :

(1) Hardware (2) Software.

(1) Hardware : It is physical part of computer system. It has following main hardware units :

(i) Central Processing Unit (CPU).

(ii) Visual Display Unit (VDU) or Terminal.

(iii) Input/Output Devices.

(iv) Storage Device.

(2) Software : Software means all those programs, which in some way can assist, all users of particular type of computer to make the best use of their machine.

Advantages of using a computer:

(i) The most powerful computer can perform

billions of calculations or arithmetic operations per second.

(ii) In general computer can process numbers, words, still pictures, moving pictures and sounds.

(iii) Computer has become a source of entertainment. You can play games listen to music, watch a video or movie, read a book or magazine or do may more things.

(iv) Communicating in the modem world has become a lot easier with a computer.

Ground Control Points (GCPs):

GCPs are features of known ground location that can be accurately located both in terms of their image coordinates (column and row numbers) on the distorted image and in terms of their ground coordinates (typically measured from map or estabilished on the ground in terms of latitude and longitude with respect to a particular projection system, say UTM or Polvconic). A leas-square regression analysis is done to interrelated the geometrically correct (map) coordinates and distorted image coordinates. Then, image is worked to have correct geometrical relationship with its corresponding ground situation.

Scanned roster images and satellite imageries are corrected for distortions by matching them with ground control points (GCPs) occurring in an image. GCPs are features of known ground location that can be accurately located on the aerial photo or satellite imagery. GCPs are located both in terms of their image coordinates (columns and row numbers) on the distorted image and in terms of their ground coordinates (typically measured from map or established on the ground in terms of latitude and longitude with respect to a particular projection system say polyconical). A least square regression analysis is done to interrelate the geometrically correct (map) coordinates and distorted image coordinates. Then image is worked to have correct geometrical relationship with its corresponding ground situation.

Digital techniques of mapping consist of following operations:

(i) Data Capture or Data Acquisition : Data about real world can be acquired from various sources. Field observations by traditional methods like aerial photos, GPS (Global Positioning System), satellite imageries, old existing maps and field manuscripts record properly verified are some of them. The field record maps and aerial photos are converted into digital form through scanning and digitisation, which can be processed further according to needs.

(ii) Geo-coding of Geo-Referencing of Roster Image : Scanned roster images and satellite imageries are corrected for distortions by matching them with Ground Control Points (GCPs) occurring in an image. GCPs are features

of known ground location that can be accurately located on the aerial photo or satellite imagery. GCPs are located both in terms of their image coordinates (columns and row numbers) on the distorted image and in terms of their ground coordinates. A least-square regression analysis is done to interrelate the geometrically correct (map) coordinates and distorted image coordinates. Then image is worked to have correct geometrical relationship with its corresponding ground situation.

(iii) Digital Fair Mapping : Geo-Coded roster image is used as a back drop to draw point-features, line features and aerial features and annotate them with proper symbols and text. Alternatively, the above features or the roster image may simply be digitized without using symbols to create cartographic data base. The

digital map may be subjected to automated cartographic processes, like generalisation, classification, etc.

(iv) Map Reproduction: The digital maps prepared through digitization of roster image in computers is used either to generate colour separates on paper or film through printer or it may be used to prepare colour composites on films through printer, or it may be used to prepare colour composites on films through printer, or it may be used to prepare colour composites on films for each colour e.g. cyan (c), magenta (m), yellow (y) and black (k). The colour separate on a paper or films are photographically merged to generate the colour composites. These colours are used to prepare plate for offset printing.

A rectangular area at the intersection of a row and a column is known as a cell.

Hard disk, floppy, tape, magnets, optical disk, compact disk, cartridge.

Average.

Polygons.

Construction of graphs.