17 Elements of GIS

Dr. Puneeta Pandey

 

1. Learning Objective

 

The objective of this module is to understand the basic concept of elements of GIS with a note on hardware and software and their role in GIS application.

 

This chapter provides an overview on the functional elements of GIS such as software, data and methods used in GIS application. This chapter highlights the use of some of the important hardware and software used in GIS namely scanner, plotter, satellite navigation system, remote sensor multibeam ecosounder, ArcView and SAGA GIS.

 

2. Introduction

 

Geographical information system (GIS) is a computer system built to capture, store, manipulate, analyse, manage and display all kinds of spatial or geographic data, answers geographic queries and provides excellent visualization capability. GIS data can be collected and details of the geographical area unveiled to serve the purpose of the GIS project that is at hand. Various sectors rely on the data and research findings to make essential decisions. A GIS system is made up of five elements: Hardware, Software, Data, People and Methods that work together to make projects successful. All of these features need to be in the balance for the GIS system to be successful. No one part can exist without other.

Fig: 1. GIS elements integrated with each other

 

3. Hardware

 

Hardware used in GIS helps in supporting the activities which are essential for geospatial analysis. These activities range from the collection of GIS data upto the interpretation of that data. A workstation is a central equipment at which GIS software runs. Other ancillary equipments are attached to the workstation. Hard copy data is converted with the help of a digitizer to digital data. Web servers also make part of the hardware for web mapping purposes ordinary in GIS and so is handheld field technology that makes data collection easy. ArcGIS Server is a server-based computer where GIS software runs on the network computer or is cloud-based. For the computer to perform well, all hardware element must have high capacity. All hardware elements function together to run a GIS software smoothly. Main hardware elements are:

 

3.1. Scanner

 

A scanner is a device that reads paper maps and converts them into very high-resolution files. The file is then used directly in the GIS as a raster backdrop or a scanned image may be vectorized using post-processing software. Scanners are typically divided into two groups: flatbed scanners – require the map to be laid out face down on a glass table; and, drum scanner – which requires the map to be attached face out to drum, that rotates.

 

3.2. Plotter

 

Inkjet plotters offer very high resolutions and quality colour reproduction for static displays. These plotters have entirely replaced the pen plotters and offer reliable, high-resolution, low maintenance colour plotting. These plotters usually make use of magenta, yellow, and black ink cartridges, which can be combined to produce any color in the spectrum. In newer models, the print head has been separated from the ink reservoir, to allow the plotter to print many plots before the reservoir needs to be replaced.

 

3.3. Monitor

 

It is the most common GIS output device that has the ability to display dynamic data in almost any colour. Depending on the amount of use, a monitor will receive many different available options. Nowadays, there are various types of monitor: CRT (cathode ray tube), LCD (Liquid Crystal Display), LED (Light Emitting Diodes) and more.

 

Fig: 2. Computer monitor

 

3.4. Satellite Navigation system

 

The Global Positioning System (GPS) is a satellite navigation system that allows the position of the receiver to be determined within meters or centimeters. GPS uses a constellation of 24 satellites having precisely known positions to enable a GPS receiver to calculate its position. Each satellite measures time accurately using an atomic clock and broadcasts a time-synchronized signal. The receiver receives the signal from four or more satellites and calculates the time differential to each satellite, which allows the distance to each satellite to be determined within a few meters. Since the satellite locations are known precisely, the receiver can then calculate its location.

Fig:3 Garmin GPS eTrex 10

 

3.5. Remote Sensors

 

The device that can obtain data about an object without coming into physical contact with that object using electromagnetic radiations is commonly known as remote sensor. Remote sensing systems are classified as passive and active. Passive remote sensing system uses an external source of electromagnetic radiation, which is usually the sun. Active remote sensing system uses their own source of light which is reflected off the target object to a sensor.

 

Fig 4: Active and Passive remote sensor

 

3.6. Multibeam Ecosounders

 

It is an advanced version of depth sounders which is used in many recreational vessels and marine mapping applications. It uses multiple beams to map the ocean depths not only directly beneath the ship, but also to each side. In the present times, two varieties of multibeam ecosounder are used. The first transmit wave from a transducer which is received by an array of microphones that are towed behind the ship; and, second transmits sound waves from a transducer and receives a reflected waves using an array of microphones that are attached to the hull of the ship.

 

Fig: 5 Anomaly detection in multibeam ecosounder seabed scans

 

4. Software

 

GIS software helps to store, analyze and display geographic information in the form of maps and reports. It provides the Graphic User Interface (GUI) for easy display and access to tools for input, visualizing, processing, editing, analyzing and querying geographic data. Data is accessed and managed through Data Management System (DBMS). Example of GIS software is ArcView 3.2, QGIS, SAGA GIS. The software elements are described below:

 

4.1. GIS Tools: Key tools to support the browsing of GIS data.

 

4.2 Relational Database Management System (RDBMS)

 

RDBMS is a type of database in which data is organized across one or more tables. The tables are associated with each other through a standard field called keys. In contrast to other database structures, RDBMS requires few assumptions about how data is related or how it is extracted from the database. The relational model has relationship between tables using primary keys, foreign keys and indices. Thus, the fetching and storing of data becomes faster. RDBMS is widely used by the enterprises and developers for storing complex and large amount of data. GIS Software retrieve from RDBMS or insert data into RDBMS.

 

4.3. Query Tools

 

The Query Tool is a production quality add-in that allows users of the ArcGIS Viewer for query a layer or table within an ArcGIS Server map service. With the add-in, users of the Application Builder can interactively build queries, end-users presenting with a simple dialog box that prompts for values to plug into the queries. The tool can be configured to query multiple fields, and query statements can be combined using logical operators.

 

4.4. Graphical User Interface (GUI)

 

GUI is a type of user interface that allows the users to interact with electronic devices through graphical icons and visual indicators such as secondary notation, typed command labels or text navigation instead of text-based user interfaces. GUI introduced in reaction to the perceived steep learning curve of command-line interfaces (CLI), which require commands to be typed on a computer keyboard.

 

4.5. Layout

 

Layout refers to the elemental arrangement on a map such as a title, legend, north arrow, scale bar, and geographic data.

 

5. GIS DATA

 

GIS data is the most important and expensive component of the GIS. It is an integration of graphics and tabular data. The graphic may be vector or raster. These data can be created in-house using GIS software or purchased from other data sources. Digitization is the process of creating the GIS data from the analog data or paper format. Digitization process involves registering of raster image using GCP (ground control point) or known coordinates. This process is widely known as georeferencing. Polygon, lines and points are created by digitizing raster image. Raster image itself registered with coordinates which are widely recognized as rectifying the image. Registered image are mostly exported in TIFF format. GIS data is two type that is vector and raster data.

 

5.1. Vector Data

 

Vector data provides a way to represent discrete data or real world features within the GIS environment. These data store information in x, y coordinate format. Vector data are of three types: Lines, Points and Area.

 

5.2. Raster Data

 

Raster data store information in a cell based manner. It can be an aerial photo or a satellite image, Digital Elevation Model (DEM). Raster images normally store continuous data.

Fig: 6 Representation of Vector and Raster Data For GIS data, the following features are essential:

 

(a)   Lineage – It is a description of the source material from which the data derived, and the methods of derivation, including all transformations involved in producing the final digital files. It includes all dates of the source material and updates and changes.

 

(b)   Logical Consistency – It deals with the logical rules of structure and attribute standards for spatial data and describes the compatibility of a datum with other data in a dataset using mathematical theories and models.

(c)   Attribute Accuracy – It is a fact about some location, set of places or features on the surface of the earth, and involves measurements of some type. Generally, some error creeps in while making these measurements, and it is important that the information be as accurate as possible while collecting these facts or carrying out the measurements.

 

(d)    Completeness – Completeness is a check to see if relevant data is missing with regard to the features and the attributes. It deals with either omission errors or spatial rules such as minimum width or area that may limit the information.

 

6. People

 

People are the key component of GIS without which nothing else would work. They are also the most complex element in the GIS; arguably the segment most prone to failure, and the only component in the system that is self-correcting and able to repair other components.

 

People in GIS are generally technical persons such as GIS manager, database administrators, specialist, programmers, analyst or a general user. People in GIS are categorized into:

 

6.1 Viewers– They are the public at large whose only need is to browse a geographic database for referential material. These constitute the largest class of users.

 

6.2 General Users– The general user is the person who uses GIS to conduct business, perform professional services and make decisions. They include facility managers, resource managers, planners, scientists, engineers, lawyers, business entrepreneurs, etc.

 

6.3 GIS specialists– Specialist is the person who makes the GIS work. They include GIS managers, database administrators, application specialists, systems analysts, and programmers. They are responsible for the maintenance of the geographic database and the provision of technical support to the other two classes of users.

 

7. Methods

 

Methods include how the data will be retrieved, input into the system, stored, managed, transformed, analyzed and finally presented in a final output. The method component of GIS includes the steps taken to answer the queries or questions that need a resolution. GIS can perform spatial analysis and answer the questions pertaining to spatial domain; and this is what differentiates this type of system from any other information systems. The transformation processes includes tasks such as setting a projection, adjusting the coordinate system, correcting any digitized errors in a data set and converting data from vector to raster or raster to vector. For successful GIS operation, a well-designed plan and business operation rules are important. Methods can vary for different organizations.

 

8. Applications

 

Application of GIS range from indigenous people, communities, research institutions, environmental scientists, health organizations, businesses and government agencies, and land use planners at all levels. Some example of GIS application given below:

 

8.1. Cartography

 

GIS can produce very high-quality maps that match or exceed the cartographic quality of maps created using traditional processes. Standard cartographic tools are available in many GIS. However, for the production of entirely new cartographic representations, or non-spatial data representations such as cartograms; GIS data or maps need to be exported to an illustration tool such as Photoshop.

 

8.2. Mapping

 

This is a central function of GIS, which provides a visual interpretation of data. GIS store data in a database and then represent it visually in the form of maps. .

 

8.3. Telecom and Network Services

 

GIS is excellent planning and decision making tool for telecom industries. GDi GISDATA enables wireless telecommunication organizations to incorporate geographic data into the sophisticated network design, planning, optimization, maintenance and activities.

 

8.4. Urban Planning

 

This technology is used to analyze the urban growth and its direction of expansion and to find suitable sites for further urban development.

 

8.5. Environmental Impact Analysis (EIA)

 

Human activities produce potential adverse environmental effects which include the construction and operation of highways, rail roads, pipelines, airports, radioactive waste disposal sites and so on. EIA is usually required to contain specific information on the magnitude and characteristics of environmental impact. The EIA can be carried out efficiently with the help of GIS and by integrating various GIS layers, assessment of natural features can be performed.

 

8.6. Agricultural Applications

 

GIS can be used to create more effective and efficient farming techniques. It can also analyze soil data and help in determining the best suited crop types besides other applications. GIS helps government agencies to manage agricultural programs that support farmers and protect the environment. It also helps in increasing food production by means of suitability analysis in different parts of the world.

 

8.7.Disaster Management and Mitigation

 

GIS is a well-developed and successful tool in disaster management and mitigation. It can help in risk management and analysis by displaying which areas are prone to natural or man-made disasters.

 

8.8.GIS in Dairy Industry

 

GIS is used in various applications in the dairy industry, such as the distribution of products, production rate, the location of shops and their selling rate.

 

8.9. Traffic Density Studies

 

It can be effectively used for the management of traffic problems that has been increasing in recent years due to ever-increasing number of vehicles plying on the roads.

 

8.10. GIS for Business

 

It is also used for managing business information based on its location. GIS can keep track of customers’ location, site business, target marketing campaigns and optimize sales territories and model retail spending patterns.

 

9. Summary

 

In this module, the reader has gained an overview of the elements of GIS that include hardware, software, people and methods. The reader has also gained a brief understanding of the raster and vector data types of GIS model. At the end, the reader has also been made familiar with the various applications of GIS. Such applications will find detailed descriptions in the modules elsewhere.

 

10. References