B.Sc. 4th Year Computational Course

7.1 Meaning of Multimedia

Multimedia refers to the integration of several forms of information media such as text, graphics, photographs, audio, video and animation within a computer-based environment. Instead of communicating information through only written text, a multimedia system combines different media so that information can be presented in a more interactive and understandable form.

A conventional text-based computer application may communicate information primarily through characters and numbers. A multimedia application can supplement the same information with photographs, diagrams, sound recordings, animations and video demonstrations. Therefore, multimedia is particularly useful when the subject requires visualization, demonstration or interaction.

Modern multimedia systems are generally digital. The individual media elements are represented using digital data and are processed, stored, transmitted and displayed by computers or other digital devices. The user may simply observe the information or may actively interact with it through menus, buttons, hyperlinks, touch interfaces or other input devices.

7.2 Characteristics of Multimedia

A multimedia system has several characteristics that distinguish it from a simple text-based information system.

1. Integration of different media

The major characteristic of multimedia is the integration of multiple media. Text can be combined with photographs, diagrams, sound, animation and video in one application.

2. Digital representation

Modern multimedia content is generally represented in digital form. Digital representation allows the information to be copied, processed, edited, stored and transmitted using computers.

3. Interactivity

Interactive multimedia allows users to control the sequence or type of information they receive. For example, a student may select a particular chapter, play a video, pause it, return to an earlier topic or open additional information.

4. User control

The user can often determine how information is accessed. Menus, hyperlinks, buttons and navigation systems provide control over the presentation.

5. Non-linear presentation

Unlike a conventional book in which pages are normally read in sequence, multimedia can provide non-linear navigation. Hyperlinks allow the user to move between related topics.

6. Large storage requirement

Audio, video and high-resolution images require considerably more storage than ordinary text. Therefore, multimedia systems require adequate storage capacity.

7. Time-dependent media

Audio, video and animation depend on time. Their correct presentation requires appropriate timing and synchronization.

8. Computer-based presentation

Multimedia applications generally require hardware and software capable of processing and presenting different media formats.

7.3 Elements of Multimedia

The major elements of multimedia are text, graphics, images, audio, video and animation. These elements may be used individually or combined within a single application.

7.4 Text in Multimedia

Text is one of the most fundamental components of multimedia. Even highly visual applications require text for titles, labels, menus, instructions, descriptions and explanations.

Text can be presented in different fonts, sizes, styles and colours. However, excessive use of decorative fonts can reduce readability. Multimedia designers therefore select fonts according to the purpose and audience of the application.

Types of text

• Plain text
• Formatted text
• Hypertext
• Interactive text
• Numerical text
• Text used in menus and buttons

Hypertext is particularly important in interactive multimedia because it allows one information element to be connected to another. A user can click a hyperlink and move directly to a related page or section.

7.5 Graphics

Graphics are visual representations created or processed using computers. They may be used to simplify complex information, illustrate concepts, display scientific structures or improve the appearance of a multimedia application.

Graphs and diagrams are particularly useful in scientific education. For example, a multimedia application can display a biological diagram together with labels and animation showing the movement of different structures.

Major types of computer graphics

• Raster graphics
• Vector graphics
• 2-dimensional graphics
• 3-dimensional graphics

Raster graphics

Raster graphics represent an image as a grid of pixels. Each pixel contains information about the colour or intensity of a small portion of the image. Photographs are commonly represented as raster images.

Vector graphics

Vector graphics represent objects using mathematical descriptions such as lines, curves and geometric shapes. Because the objects are mathematically defined, vector graphics can generally be resized without the same type of pixelation associated with raster images.

7.6 Digital Images

A digital image is an image represented as numerical data that can be stored and processed by a computer. A digital image may be obtained using a digital camera, scanner, medical imaging device or computer graphics software.

The quality of a digital image is affected by factors such as resolution, colour depth, compression and image format.

Resolution

Resolution refers to the amount of detail that can be represented in an image. In a raster image, resolution is commonly expressed using the number of pixels in width and height.

For example, an image with dimensions 1920 × 1080 contains:

Thus, the image contains approximately 2.07 million pixels.

Colour depth

Colour depth refers to the number of bits used to represent the colour of each pixel. Greater colour depth allows a larger number of possible colours.

For an image with n bits per pixel, the number of possible colour values is:

For example, an 8-bit image can represent:

A 24-bit colour image can represent:

7.7 Audio

Audio is the representation of sound in a multimedia system. Speech, music, environmental sounds and narration can be included in multimedia applications.

Computers commonly store sound in digital form. During digital audio recording, an analogue sound wave is sampled at regular intervals and each sample is converted into a numerical value.

Important audio concepts

• Sampling
• Sampling rate
• Amplitude
• Bit depth
• Channels
• Compression

Sampling rate

Sampling rate is the number of audio samples taken per second. It is usually expressed in hertz.

For example, a sampling rate of 44.1 kHz means that 44,100 samples are taken each second.

Higher sampling rates can represent higher-frequency components of sound, although they also require more storage or transmission capacity.

Bit depth

Bit depth determines the number of possible amplitude values used for each sample. Greater bit depth generally provides greater amplitude resolution.

7.8 Video

Video is a sequence of still images called frames displayed rapidly in succession so that the human observer perceives continuous motion. Digital video may also contain synchronized audio.

Important properties of digital video include resolution, frame rate, colour depth, compression and file format.

Frame rate

Frame rate represents the number of video frames displayed per second. It is generally expressed in frames per second (fps).

A higher frame rate can provide smoother apparent motion, although it also increases the amount of data that may need to be processed or stored.

7.9 Animation

Animation is the technique of creating an appearance of movement by displaying a sequence of images or changing graphical objects over time.

Animation can be especially useful for explaining processes that are difficult to observe directly. In scientific education, for example, animation can demonstrate the movement of molecules, biological processes or changes occurring within a system.

Types of animation

• Traditional animation
• 2-dimensional computer animation
• 3-dimensional animation
• Motion graphics
• Character animation
• Scientific animation

7.10 Multimedia Computer System

A multimedia computer system is a computer system capable of processing, storing and presenting multiple forms of media such as text, images, audio, animation and video.

             MULTIMEDIA COMPUTER SYSTEM
                       |
        --------------------------------
        |              |               |
      INPUT         PROCESSING       OUTPUT
        |              |               |
  Camera/Scanner    CPU/GPU        Monitor
  Microphone        Memory         Speakers
  Keyboard          Storage        Projector
  Mouse             Software       Printer
        |
        v
  Multimedia Data

Major hardware components

• CPU
• RAM
• Storage devices
• Graphics processing hardware
• Sound card/audio interface
• Monitor/display
• Speakers/headphones
• Microphone
• Camera
• Scanner
• Keyboard and mouse
• Projector

7.11 Multimedia Software

Multimedia software is used to create, edit, manage, present or play multimedia information.

Examples include image editors, audio editors, video editors, presentation programs, animation software, media players and authoring systems.

Functions of multimedia software

• Creating multimedia content
• Editing photographs
• Recording and editing sound
• Editing video
• Creating animation
• Combining multiple media
• Adding navigation and interaction
• Playing multimedia files

7.12 Multimedia Authoring

Multimedia authoring is the process of combining different multimedia elements into an integrated application. An authoring system provides tools through which a developer can arrange text, images, audio, video, animation and navigation.

An authoring environment may use menus, timelines, icons, scripts or other methods to control the presentation of multimedia information.

7.13 Applications of Multimedia

Multimedia has applications in almost every field where information must be communicated effectively.

1. Education

Multimedia is widely used in classroom teaching, online education, computer-based learning and laboratory demonstrations. Complex concepts can be explained through diagrams, animation, narration and video demonstrations.

2. Medicine

Medical education uses multimedia for anatomical visualization, medical imaging, surgical demonstrations, patient education and simulation-based training.

3. Science

Scientific multimedia can demonstrate experimental procedures, biological processes, chemical reactions, geological processes and computer simulations.

4. Business

Businesses use multimedia in advertising, product demonstrations, training programs, presentations and corporate communication.

5. Entertainment

Movies, computer games, music applications and interactive entertainment depend heavily on multimedia technologies.

6. Public information

Museums, exhibitions, libraries and public institutions use interactive multimedia systems to communicate information to visitors.

8.1 Introduction to Computer Security

Computer security is the protection of computer systems, networks, software and information from unauthorized access, misuse, alteration, destruction or disruption.

The importance of computer security has increased because computers are used for communication, financial transactions, scientific research, education, health services, government services and storage of personal information.

A security failure may result in loss of data, financial loss, privacy violations, interruption of services, reputational damage or damage to computer systems.

8.2 Objectives of Computer Security

The traditional objectives of information security are commonly described using the CIA triad.

                 INFORMATION SECURITY
                         |
             -------------------------
             |           |           |
       CONFIDENTIALITY INTEGRITY  AVAILABILITY
             |           |           |
        Prevent       Prevent       Ensure
        unauthorized unauthorized   authorized
        disclosure    alteration    access

Confidentiality

Confidentiality means protecting information from unauthorized disclosure. Only authorized users should be able to access sensitive information.

Integrity

Integrity means maintaining the accuracy and completeness of data. Unauthorized persons should not be able to modify information without detection or authorization.

Availability

Availability means ensuring that authorized users can access systems and information when required.

8.3 Threat, Vulnerability and Attack

These three concepts are related but should not be treated as identical.

Threat

A threat is a potential event, action or circumstance that can cause harm to a computer system or information.

Vulnerability

A vulnerability is a weakness in hardware, software, configuration, procedure or human behaviour that may be exploited to cause harm.

Attack

An attack is an attempt to exploit a vulnerability in order to obtain unauthorized access, alter information, disrupt services or otherwise compromise a system.

8.4 Passive and Active Attacks

8.5 Malware

Malware means malicious software. It refers to software intentionally designed to perform harmful, unauthorized or unwanted activities on a computer system.

Different types of malware have different methods of operation.

Computer virus

A virus is malicious code that attaches itself to another file or program and may replicate when the infected host is executed. Depending on its type, a virus can modify files, corrupt information, consume resources or perform other harmful actions.

Worm

A worm is a malicious program capable of spreading from one system to another, often through networks, without requiring the same type of host-file attachment associated with many traditional viruses.

Trojan horse

A Trojan horse is a malicious program disguised as legitimate or useful software. The user may install or execute it believing that the program is safe.

Spyware

Spyware is software designed to monitor activities or collect information without appropriate authorization.

Ransomware

Ransomware is malware that attempts to deny access to data or systems, often by encrypting files, and commonly demands payment in exchange for restoration or a decryption mechanism.

Adware

Adware is software that displays unwanted advertising. Some forms may also track user activity or create additional security and privacy risks.

Rootkit

A rootkit is a collection of tools or techniques designed to maintain unauthorized privileged access while attempting to conceal its presence.

Keylogger

A keylogger records keystrokes. Malicious keyloggers may be used to capture passwords or other sensitive information.

8.6 Phishing

Phishing is a social-engineering technique in which an attacker attempts to deceive a user into providing sensitive information or performing an unsafe action.

Phishing messages may imitate banks, organizations, educational institutions, online services or other trusted entities.

Common warning signs

• Unexpected requests for passwords or financial information
• Urgent or threatening language
• Suspicious links
• Unexpected attachments
• Spelling or formatting abnormalities
• Requests to bypass normal security procedures
• Messages from unexpected senders

8.7 Social Engineering

Social engineering refers to manipulation of people to obtain information, access or an action that compromises security. It exploits human behaviour rather than relying only on technical weaknesses.

Examples include phishing, impersonation, fraudulent phone calls, pretexting, baiting and other forms of deception.

Security awareness is therefore an essential component of computer security.

8.8 Hacking

Hacking broadly refers to gaining access to or manipulating computer systems by exploiting technical or other weaknesses. The term is used in different contexts, and not all hacking activity has the same purpose.

Authorized security testing, commonly called ethical hacking or penetration testing, is performed with permission to identify vulnerabilities so that they can be corrected.

Unauthorized access, in contrast, can cause security breaches, privacy violations, data loss and disruption.

8.9 Cryptography

Cryptography is the science and practice of protecting information by transforming it so that unauthorized persons cannot understand or properly use it.

The transformation of readable information into an unintelligible form is called encryption, while converting encrypted information back into an understandable form is called decryption.

                 ORIGINAL MESSAGE
                        |
                        |
                    ENCRYPTION
                        |
                        v
                 CIPHERTEXT
                        |
                        |
                    DECRYPTION
                        |
                        v
                 ORIGINAL MESSAGE

Plaintext

Plaintext is the original readable information.

Ciphertext

Ciphertext is the transformed information produced through encryption.

Key

A cryptographic key is information used by a cryptographic algorithm to control encryption or decryption.

8.10 Symmetric-Key Cryptography

In symmetric-key cryptography, the same secret key, or corresponding secret-key material, is used for encryption and decryption.

              SECRET KEY
                   |
                   v
PLAINTEXT ---> ENCRYPTION ---> CIPHERTEXT
                               |
                               |
                         DECRYPTION
                               ^
                               |
                         SECRET KEY
                               |
                               v
                           PLAINTEXT

The major advantage of symmetric cryptography is that it can be efficient and suitable for processing large amounts of data.

A major challenge is secure key distribution. The communicating parties must have access to the secret key without allowing an unauthorized person to obtain it.

8.11 Public-Key Cryptography

Public-key cryptography, also called asymmetric cryptography, uses a pair of mathematically related keys: a public key and a private key.

The public key can generally be distributed, while the private key must be kept secret by its owner.

             PUBLIC KEY              PRIVATE KEY
                 |                       |
                 v                       v
             Encryption              Decryption
                 |                       |
                 v                       v
              MESSAGE  ------------> MESSAGE
                    encrypted data

Public-key cryptography can help solve some key-distribution problems associated with symmetric systems. It is also important in digital signatures and secure communication protocols.

8.12 Symmetric vs Public-Key Cryptography

8.13 Digital Signature

A digital signature is a cryptographic mechanism used to provide evidence about the origin and integrity of digital information.

Digital signatures can help establish that a message or document was signed using the corresponding private key and that the signed data has not been altered in a manner detectable by the verification process.

Digital signatures are important in electronic documents, certificates, secure communication and online transactions.

8.14 Firewall

A firewall is a security mechanism that monitors and controls network traffic according to predefined rules.

                 INTERNET
                    |
                    |
              +-------------+
              |  FIREWALL   |
              |             |
              | Rule-based  |
              | filtering   |
              +-------------+
                    |
                    |
             INTERNAL NETWORK
                    |
          ---------------------
          |         |         |
       Computer   Server    Printer

A firewall may control traffic based on factors such as source, destination, protocol, port or other characteristics depending on the firewall technology.

Functions of a firewall

• Controls network traffic
• Blocks unauthorized connections according to rules
• Allows permitted traffic
• Helps reduce exposure of internal systems
• Can assist in monitoring network activity
• Can contribute to network security policy enforcement

A firewall is not a complete security solution. It should be combined with secure configuration, authentication, software updates, anti-malware measures, backups and user awareness.

8.15 Antivirus Software

Antivirus software is designed to detect, block and remove or quarantine malicious software. Modern security products may also provide protection against suspicious behaviour and other categories of threats.

Important functions

• Scanning files
• Scanning removable media
• Real-time monitoring
• Detecting known malicious patterns
• Identifying suspicious behaviour
• Quarantining suspicious files
• Removing detected malware

8.16 Authentication and Authorization

Authentication is the process of verifying the identity of a user or system.

Authorization determines what an authenticated user is permitted to access or perform.

8.17 Password Security

Passwords remain an important authentication mechanism. Weak or reused passwords can create significant security risks.

Good password practices

• Use sufficiently long passwords.
• Avoid easily guessed personal information.
• Do not reuse the same password across important accounts.
• Use a password manager where appropriate.
• Enable multi-factor authentication where available.
• Never share passwords unnecessarily.
• Change compromised passwords promptly.

8.18 Backup and Recovery

A backup is a separate copy of important data maintained so that information can be restored after accidental deletion, hardware failure, malware, theft or other incidents.

Backups are especially important against ransomware and accidental data loss.

Common backup approaches

• Full backup
• Incremental backup
• Differential backup
• Local backup
• Remote backup
• Cloud-based backup

8.19 Computer Security Measures

1. Keep operating systems and applications updated.
2. Use strong authentication.
3. Use multi-factor authentication where possible.
4. Install reputable security software.
5. Use firewalls appropriately.
6. Maintain regular backups.
7. Encrypt sensitive information where appropriate.
8. Avoid suspicious links and attachments.
9. Use secure networks.
10. Restrict unnecessary user privileges.
11. Monitor security events.
12. Educate users.
13. Develop and enforce security policies.

9.1 Introduction to GIS

GIS stands for Geographic Information System. It is a computer-based system used to collect, store, manage, analyze and display information associated with geographic locations.

The major feature of GIS is its ability to connect information about an object or phenomenon with its geographic location. For example, a GIS database can store the location of a river together with information about its name, length, water quality and surrounding land use.

9.2 Components of GIS

A GIS generally consists of five major components: hardware, software, data, people and methods.

                    GIS
                     |
       --------------------------------
       |       |       |       |      |
    Hardware Software Data   People Methods
       |       |       |       |      |
   Computer  GIS     Spatial  Users  Procedures
   Storage   tools   Attribute Analysts Standards
   GPS       Database Data    Experts Workflows

Hardware

Hardware includes computers, storage devices, scanners, GPS receivers, digitizers, servers, monitors, printers and other devices used for GIS data collection, processing and presentation.

Software

GIS software provides tools for data entry, storage, editing, analysis, visualization and map production.

Data

Data are the foundation of a GIS. Spatial data describe geographic location, while attribute data describe characteristics associated with spatial features.

People

GIS requires users, analysts, database managers, surveyors, cartographers, planners, scientists and other professionals.

Methods

Methods include procedures, standards, workflows and analytical techniques used to collect and process GIS information.

9.3 Spatial Data

Spatial data describe the location, shape and spatial relationship of geographic features.

Examples include the locations of roads, rivers, buildings, boundaries, forests and sampling sites.

Spatial information can be represented using coordinates, lines, points, polygons or grids.

9.4 Non-Spatial or Attribute Data

Attribute data provide descriptive information associated with spatial features.

For example, a point representing a water sampling station may have attributes such as station name, pH, temperature, microbial count and sampling date.

9.5 Vector Data Model

The vector data model represents geographic features using points, lines and polygons.

Point

A point represents a feature whose location is represented by a single coordinate or location. Examples include wells, sampling stations and individual trees.

Line

Lines represent linear features such as roads, rivers and pipelines.

Polygon

Polygons represent areas such as lakes, administrative regions, forest areas and agricultural fields.

VECTOR DATA

POINT
   •        Sampling site

LINE
   ----------------
        River

POLYGON

       __________
      /          \
     /            \
    /______________\
       Forest area

9.6 Raster Data Model

Raster data represent geographic information as a regular grid of cells or pixels. Each cell contains a value representing a property of the area covered by that cell.

Raster data are particularly suitable for continuous phenomena such as elevation, temperature, rainfall, satellite imagery and vegetation indices.

RASTER DATA

+---+---+---+---+---+
| 2 | 2 | 3 | 4 | 4 |
+---+---+---+---+---+
| 2 | 3 | 3 | 4 | 5 |
+---+---+---+---+---+
| 1 | 2 | 3 | 5 | 5 |
+---+---+---+---+---+
| 1 | 1 | 2 | 4 | 5 |
+---+---+---+---+---+

Each cell stores a value.

9.7 Vector and Raster Comparison

9.8 GIS Data Input

GIS data can be obtained from several sources.

• GPS measurements
• Satellite imagery
• Aerial photography
• Existing maps
• Survey data
• Remote-sensing data
• Digitization
• Existing databases
• Field observations

Before analysis, data may need to be cleaned, transformed, georeferenced and converted into an appropriate coordinate system.

9.9 Digitization

Digitization is the process of converting information from analogue maps or other sources into digital geographic data.

For example, roads, rivers and boundaries shown on a paper map can be digitized as digital line or polygon features.

9.10 Georeferencing

Georeferencing is the process of assigning geographic coordinates to an image, map or dataset so that it can be correctly positioned in a coordinate reference system.

It is important when scanned maps, aerial photographs or other spatial information must be integrated with geographic datasets.

9.11 Coordinate System

A coordinate system provides a method for specifying the geographic position of a location.

Geographic coordinate systems commonly use latitude and longitude. Projected coordinate systems transform the Earth's curved surface into a planar representation using a map projection.

9.12 Map Projection

A map projection is a mathematical method for representing the curved surface of the Earth on a flat map.

Because a curved surface cannot generally be transformed onto a flat surface without distortion, different projections are designed for different purposes.

Map projections may preserve or emphasize properties such as area, shape, distance or direction, but no ordinary projection can preserve all of these properties perfectly over an entire map.

9.13 GIS Data Analysis

GIS becomes particularly powerful because it can perform analysis on spatial and attribute data.

Spatial query

A spatial query retrieves features according to their geographic location or spatial relationship.

Attribute query

An attribute query retrieves features according to information stored in their attribute tables.

Buffering

Buffering creates a zone around a geographic feature at a specified distance. For example, a buffer around a river can be used to study land use within a specified distance of the river.

Overlay analysis

Overlay combines two or more spatial datasets to identify relationships between them.

Network analysis

Network analysis studies connected geographic systems such as roads, transportation networks and pipelines.

9.14 GIS Input-Process-Output Model

          GIS INPUT
              |
              v
    ---------------------
    | Spatial Data       |
    | Attribute Data     |
    | GPS                |
    | Remote Sensing     |
    | Existing Maps      |
    ---------------------
              |
              v
          PROCESSING
              |
       ----------------
       | Editing       |
       | Query         |
       | Overlay       |
       | Buffer        |
       | Analysis      |
       ----------------
              |
              v
           OUTPUT
              |
       ----------------
       | Maps          |
       | Tables        |
       | Charts        |
       | Reports       |
       | Statistics    |
       ----------------

9.15 Applications of GIS

Agriculture

GIS can be used to map agricultural land, analyze soil characteristics, monitor crops, identify irrigation requirements and support precision agriculture.

Forestry

GIS can be used to map forest distribution, monitor changes in forest cover, identify areas affected by fire and support forest management.

Public health

GIS can display the geographic distribution of diseases and health services. Spatial analysis can help researchers examine relationships between disease occurrence and environmental or demographic factors.

Disaster management

GIS can support hazard mapping, vulnerability assessment, emergency planning, evacuation planning and resource allocation.

Urban planning

GIS can integrate information about roads, buildings, population, land use and infrastructure to support urban development planning.

Environmental management

GIS can be used to monitor land-use change, pollution, forest degradation, water resources and habitat distribution.

Water-resource management

GIS can assist in mapping watersheds, rivers, groundwater resources, drainage patterns and water-quality sampling locations.

9.16 Remote Sensing

Remote sensing is the acquisition of information about an object, area or phenomenon without direct physical contact with the object being observed.

Earth observation satellites and aircraft can detect reflected or emitted electromagnetic energy from the Earth's surface. The resulting information can be processed to produce images and other measurements.

9.17 Principle of Remote Sensing

The basic principle of remote sensing involves an energy source, interaction of electromagnetic radiation with the Earth's surface, detection by a sensor, transmission of data and processing and interpretation of the resulting information.

             SUN / ENERGY SOURCE
                    |
                    v
          Electromagnetic energy
                    |
                    v
             EARTH SURFACE
                    |
        -------------------------
        |          |            |
    Reflection  Absorption   Transmission
        |
        v
       SENSOR
        |
        v
  Data transmission
        |
        v
   Image processing
        |
        v
 Interpretation
        |
        v
   INFORMATION

9.18 Electromagnetic Radiation

Electromagnetic radiation is energy that travels through space in the form of electromagnetic waves. Remote sensing depends on the interaction between electromagnetic radiation and materials on the Earth's surface.

Different materials interact with electromagnetic energy differently. This difference makes it possible to distinguish vegetation, water, soil, buildings and other surface materials.

9.19 Electromagnetic Spectrum

The electromagnetic spectrum includes a broad range of radiation classified according to wavelength or frequency.

Important regions used in remote sensing include visible light, infrared and microwave regions.

9.20 Interaction of Radiation with the Atmosphere

Before reaching the Earth's surface or sensor, electromagnetic radiation may interact with the atmosphere. The major processes include scattering and absorption.

Scattering

Scattering changes the direction of radiation due to interaction with particles or molecules in the atmosphere.

Absorption

Atmospheric gases can absorb particular wavelengths of electromagnetic radiation.

Atmospheric effects are therefore important in remote-sensing data processing and interpretation.

9.21 Interaction with Earth's Surface

When electromagnetic radiation reaches the Earth's surface, part of the energy may be reflected, absorbed or transmitted.

The relative amounts depend on the properties of the material and the wavelength of the radiation.

For example, vegetation has characteristic spectral responses that can help distinguish it from bare soil or water.

9.22 Sensors

A sensor is a device that detects and records electromagnetic energy. Sensors are important components of remote-sensing systems.

Passive sensors

Passive sensors detect naturally available electromagnetic energy, such as reflected sunlight or emitted thermal radiation.

Active sensors

Active sensors transmit their own energy toward the target and measure the returned signal.

Radar is an important example of an active remote-sensing system.

9.23 Platforms

A platform carries the remote-sensing sensor.

Ground-based platforms

Sensors are installed on the ground for detailed local measurements.

Airborne platforms

Aircraft or other aerial platforms carry sensors over the area being studied.

Spaceborne platforms

Satellites carry sensors to observe large geographic areas repeatedly.

9.24 Resolution in Remote Sensing

Resolution describes the ability of a remote-sensing system to distinguish information. Four major forms are spatial, spectral, temporal and radiometric resolution.

Spatial resolution

Spatial resolution refers to the size of the smallest ground area represented by an individual image pixel.

Spectral resolution

Spectral resolution describes the ability of a sensor to distinguish different wavelength bands.

Temporal resolution

Temporal resolution refers to how frequently a sensor can obtain observations of the same area.

Radiometric resolution

Radiometric resolution refers to the sensitivity of a sensor to differences in energy intensity.

9.25 Image Interpretation

Image interpretation is the process of extracting useful information from remote-sensing images.

Common visual interpretation elements include:

• Tone or colour
• Texture
• Shape
• Size
• Pattern
• Shadow
• Site
• Association

The interpreter combines these characteristics with contextual knowledge to identify features in an image.

9.26 Applications of Remote Sensing

Agriculture

Remote sensing can monitor vegetation condition, crop distribution, crop stress, irrigation patterns and land-use changes.

Forestry

Satellite and airborne imagery can be used to monitor forest cover, deforestation, forest fires and vegetation changes.

Geology

Remote sensing can assist geological mapping by identifying differences in surface materials, structures and landforms.

Hydrology

Remote sensing can assist in mapping water bodies, monitoring flooding and studying watershed characteristics.

Disaster management

Remote sensing provides rapid information over large areas after floods, landslides, earthquakes, forest fires and other disasters.

Environmental monitoring

Remote sensing can be used to monitor vegetation change, deforestation, land degradation, water bodies and urban expansion.

Urban planning

Repeated satellite observations can show changes in settlement, transportation networks and land use.

9.27 GIS and Remote Sensing Relationship

GIS and remote sensing are closely related but are not identical. Remote sensing primarily provides information collected remotely, while GIS provides a framework for storing, integrating, analyzing and displaying spatial information from remote sensing and many other sources.

10.1 Introduction to Computer Laboratory

The practical component of a computational course provides students with direct experience in using computers and common application software. Practical knowledge is important because theoretical understanding of computer concepts becomes more useful when students can apply the concepts to actual tasks.

The laboratory component generally involves operating-system operations, word processing, spreadsheet calculations, presentations, Internet use and electronic mail.

10.2 Operating System Practical

An operating system is system software that manages computer hardware and provides an environment in which application programs can run.

Major functions of an operating system

• Process management
• Memory management
• File management
• Device management
• User-interface management
• Security and access control
• Resource allocation

10.3 File and Folder Management

Files are collections of information stored on a computer, while folders or directories are used to organize files and other folders. Good file management makes information easier to locate, protect and back up.

Common operations

1. Create a folder.
2. Open a folder.
3. Create a file.
4. Rename a file.
5. Copy a file.
6. Move a file.
7. Delete a file.
8. Restore a file from the recycle/trash area where applicable.
9. Search for a file.
10. View file properties.

Practical procedure: Creating a folder

1. Open the file manager.
2. Navigate to the desired location.
3. Use the New Folder command.
4. Enter an appropriate folder name.
5. Press Enter or confirm creation.

10.4 Word Processor

A word processor is application software used to create, edit, format, store and print text documents.

Common word-processing functions

• Typing and editing text
• Changing fonts
• Changing font size
• Bold, italic and underline
• Paragraph alignment
• Line spacing
• Margins and page orientation
• Headers and footers
• Page numbering
• Tables
• Images
• Spell checking
• Find and replace
• Printing

10.5 Practical: Creating a Scientific Document

A typical laboratory examination may require students to create and format a document.

Procedure

1. Open the word-processing application.
2. Create a new blank document.
3. Enter the required title.
4. Apply an appropriate heading style or formatting.
5. Enter the main body text.
6. Adjust paragraph alignment.
7. Set line spacing.
8. Insert a table if required.
9. Insert an image or figure where required.
10. Add header and footer information.
11. Insert page numbers.
12. Save the document using an appropriate filename.
13. Review the document for spelling and formatting errors.
14. Print or export the document if required.

10.6 Tables in Word Processor

Tables provide a structured way of presenting information in rows and columns.

Practical procedure

1. Place the cursor at the required location.
2. Choose the table insertion command.
3. Select the required number of rows and columns.
4. Enter data into the cells.
5. Adjust column widths.
6. Format the heading row.
7. Apply borders where appropriate.
8. Align the contents.

10.7 Find and Replace

The Find function locates a particular word or phrase in a document. The Replace function can substitute one word or phrase with another.

These tools are particularly useful when correcting repeated mistakes in a long document.

10.8 Mail Merge

Mail merge is a word-processing feature used to create multiple personalized documents from a common template and a data source.

For example, the same letter can be sent to many recipients while automatically changing the recipient's name and address.

              MAIN DOCUMENT
                    |
                    |
                    +
                    |
              DATA SOURCE
                    |
                    v
              MAIL MERGE
                    |
          --------------------
          |        |         |
       Letter  Letter      Letter
       Person1 Person2     Person3

10.9 Spreadsheet

A spreadsheet is application software designed for organizing data in rows and columns and performing calculations using formulas and functions.

A spreadsheet consists of cells arranged into rows and columns. Each cell has an address, such as A1, B5 or C10.

10.10 Types of Spreadsheet Data

• Text
• Numbers
• Dates
• Times
• Logical values
• Formulas
• Functions

10.11 Spreadsheet Formulas

A formula is an expression used to calculate a result. In most spreadsheet applications, formulas begin with an equals sign.

For example:

adds the values contained in cells A1 and B1.

Similarly:

multiplies the values in C2 and D2.

10.12 Basic Spreadsheet Functions

Common spreadsheet functions include SUM, AVERAGE, MAX, MIN and COUNT.

Example

Suppose five observations are stored in cells B2:B6:

calculates their total.

calculates their arithmetic mean.

returns the largest value.

returns the smallest value.

10.13 Relative and Absolute Cell References

Cell references are important when formulas are copied from one cell to another.

Relative reference

A relative reference changes when the formula is copied to another cell.

Example:

When copied one row downward, it may become:

Absolute reference

An absolute reference remains fixed when a formula is copied. It is commonly represented using the dollar sign.

The row and column remain fixed when the formula is copied.

10.14 Percentage Calculation in Spreadsheet

Percentage can be calculated using:

For example, if a student obtains 72 marks out of 90:

In a spreadsheet, if obtained marks are in B2 and total marks are in C2, the formula can be written as:

10.15 Spreadsheet Sorting and Filtering

Sorting arranges data according to a selected field or value. Filtering displays only records satisfying selected conditions.

For example, a dataset of students can be sorted according to marks from highest to lowest or filtered to display only students whose marks exceed a specified value.

10.16 Charts in Spreadsheet

Charts present numerical information graphically. They can make patterns and comparisons easier to understand.

Common chart types

• Column chart
• Bar chart
• Line chart
• Pie chart
• Area chart

General procedure for creating a chart

1. Enter data into the spreadsheet.
2. Select the data range.
3. Choose the chart command.
4. Select an appropriate chart type.
5. Add chart title.
6. Label axes where applicable.
7. Check the chart for accuracy.
8. Save the workbook.

10.17 Practical Spreadsheet Example

If practical marks are in B2 and theory marks are in C2, the total can be calculated using:

For Student A, the result is:

The same formula can then be copied to the other rows.

10.18 Presentation Software

Presentation software is used to create and display information in the form of slides. It is commonly used for teaching, seminars, scientific presentations and business communication.

Important presentation components

• Slides
• Text
• Images
• Tables
• Charts
• Audio
• Video
• Animations
• Transitions
• Speaker notes

10.19 Creating a Presentation

1. Open presentation software.
2. Create a new presentation.
3. Select a suitable theme or layout.
4. Create a title slide.
5. Add additional content slides.
6. Use concise points rather than excessively long paragraphs.
7. Insert relevant figures and tables.
8. Add charts when numerical data are presented.
9. Apply consistent formatting.
10. Add appropriate transitions.
11. Use animation only when it improves understanding.
12. Review the presentation.
13. Save the presentation.

10.20 Principles of Good Presentation Design

A scientific presentation should be clear, organized and easy to read. Excessive text, unnecessary animation, poor contrast and inconsistent formatting reduce the effectiveness of a presentation.

A good presentation generally contains a clear title, logical sequence, readable text, appropriate figures and a conclusion.

10.21 Internet

The Internet is a worldwide interconnected system of computer networks that communicates using standardized networking protocols. It provides services such as the World Wide Web, email, file transfer, communication and online information services.

10.22 World Wide Web

The World Wide Web is a service operating over the Internet that allows users to access interconnected web resources using web browsers and web technologies.

The Web should therefore not be treated as exactly synonymous with the Internet. The Internet is the underlying global network infrastructure, while the Web is one of the services that operates on it.

10.23 Web Browser

A web browser is software used to access and display web pages and other web resources.

Common browser functions

• Opening web pages
• Using hyperlinks
• Searching the Web
• Saving bookmarks
• Downloading files
• Managing browsing history
• Managing cookies and site permissions
• Private browsing features

10.24 Search Engine

A search engine is an online service that helps users find information available on the Web.

Effective searching requires appropriate keywords. Adding specific terms generally produces more focused results than using very broad queries.

Examples of search strategies

• Use specific keywords.
• Use quotation marks for exact phrases where supported.
• Include scientific terminology where appropriate.
• Exclude irrelevant terms when the search system supports it.
• Evaluate the credibility of sources.

10.25 Email

Electronic mail, commonly called email, is a system for sending and receiving digital messages over computer networks.

Major email fields

• To
• CC
• BCC
• Subject
• Message body
• Attachment

To

The To field contains the primary recipient or recipients.

CC

CC means carbon copy. Recipients listed in CC normally receive a copy of the message and their addresses are visible to other recipients.

BCC

BCC means blind carbon copy. Recipients placed in BCC are generally hidden from other recipients.

10.26 Email Attachments

An attachment is a file sent along with an email message. Documents, spreadsheets, images and other file types may be attached, subject to the restrictions of the email service.

Good practices

• Use a meaningful filename.
• Check the correct recipient before sending.
• Confirm that the attachment is actually included.
• Avoid opening unexpected attachments.
• Compress large files when appropriate.
• Use a secure alternative when sending highly sensitive information.

10.27 Email Etiquette

• Use a meaningful subject.
• Use appropriate and respectful language.
• Keep the message organized.
• Check spelling and grammar.
• Do not send unnecessary mass emails.
• Use CC and BCC appropriately.
• Do not forward suspicious messages.
• Check recipients carefully before sending confidential information.
• Respond within a reasonable period when appropriate.

10.28 Safe Internet Practices

Internet safety requires both technical controls and responsible user behaviour.

1. Use strong authentication.
2. Keep software updated.
3. Avoid suspicious links.
4. Do not download unknown software.
5. Use secure connections for sensitive activities.
6. Protect personal information.
7. Use reputable security software.
8. Back up important information.
9. Verify unusual requests.
10. Use caution with public computers and networks.