LIST OF TOPICS / INDEX

REMOTE SENSING, GIS and GPS

Fundamentals of Remote Sensing

• Why Remote Sensing?
• What is Remote Sensing?
• Remote Sensing: Basic Principle
• An Overview of Remote Sensing
• Stages in Remote Sensing
• Types of Remote Sensing
• Electromagnetic Spectrum
• Spectral Reflectance
• Satellite Sensor Resolutions
• Understanding Hyperspectral Remote Sensing

About Satellite Images

• A Note on Digital Satellite Images
• ‘Visually Reading’ a Satellite Image
• ‘Digitally Reading’ a Satellite Image

Applications

• Applications of Remote Sensing
• Thermal Pollution & Remote Sensing

Satellite Sensors

• Popular Remote Sensing Systems
• CARTOSAT: A Milestone achieved by India

Miscellaneous

• Before Selecting a Satellite Image!!
• Chronology of Remote Sensing

Digital Image Processing

• Digital Image Processing: An Introduction

Geographic Information System (GIS)

Understanding GIS

• Introduction & Definition
• Components of GIS
• Types of GIS Data
• Vector Data Vs. Raster Data
• Human Resources in GIS
• GIS SOFTWARE-1:ESRI
• GIS SOFTWARE-2:Manifold
• Georegistration: Basics & Right Methods
• Digitization: Basics and Right Methods
• Books on Remote Sensing & GIS
• QGIS for Beginners (Video)
  

Drones for GIS / Remote Sensing

• Drones: An Overview and Benefits
• Applications of Drone Mapping

Global Positioning System (GPS)

• GPS: An Introduction
• Selecting Right GPS 
• Things to Remember while Starting GPS Survey

Please feel free to suggest topics of your interest in comment box.

GPS: An Introduction

Global Positioning System (GPS) is satellite-based navigation system which records and displays location of an object on earth (in terms of coordinates, e.g. latitude and longitude). It also shows height of a place above mean sea level. Like many other remote sensing and GIS devices, application of GPS devices was also first started for military and defense purposes. Slowly these devices made entry into public domain for various civilian uses. Now GPS has become so popular that it is being integrated in new generation mobile phones. 

A GPS device receives signals from satellites and these signal codes are processed & converted into values showing position, time and velocity (what we see on screen of GPS device). The instrument to which we generally call ‘GPS’ is basically a GPS receiver and it is a small part of a large system. A complete Global Positioning System consists of three segments- space segment, control segment and user segment. 

A Handheld GPS

Space Segment 

Space segment consists of dedicated satellites for Global Positioning System and are referred as space vehicles (SVs). There are twenty four satellites in a nominal GPS constellation. Out of these twenty four satellites three are spare satellites which start operating if some of the functional twenty one satellites have some operational problem. These satellites remain in six orbital planes (four in each) and are positioned such that five to eight of these SVs visible from any place on the earth at a given point of time. 

Control Segment 

The control segment consists of tracking stations located around all over world. There are master control station and monitoring stations in control segment. 

User Segment User segment of GPS is what we uses i.e. GPS receiver. It also includes the GPS user community. A GPS receiver consists of a screen for displaying information, buttons to operate it and antenna to receive signals from satellites. 

The antenna may be in-built in receiver instrument or it may be externally attached to it. Signals from minimum four satellites are required for a GPS receiver to compute location (x, y & z) and time (t). GPS receivers are essential part of navigation system of air crafts and ships. Now-a-days these are also being integrated in surface-based navigation (trains, buses, cars & other vehicles).

Please see INDEX for complete list of topics

GIS: Introduction and Definition

Geographic Information System (GIS) is becoming more & more popular amongst decision makers as it enables them to quickly refer the GIS outputs which help them in solving problems and making right decisions. Visualization of features, converting data into need-based maps (thematic maps) and capability of providing solutions by taking into account overall scenario of an area are some of the virtues of GIS due to which it is being implemented across a number of sectors and departments (e.g., transportation, forestry, environment, disaster management, urban planning, health etc). 

We often feel difficulty to understand and visualize a problem just by seeing data or figures. We are more comfortable with visual representation of a problem that’s what GIS is giving to us (that too with the true representation of real-world). 

Definition GIS is made up of three terms- Geographic, Information and System. In literal meaning Geographic Information System is a System containing Information which is geographic in nature. GIS can be defined as - A System which involves collecting/capturing, storing, processing. manipulating, analyzing, managing, retrieving and displaying data (information) which is, essentially, referenced to the real-world or the earth (i.e. geographically referenced).

Explanation of the Definition

We have used many term in the definition of GIS mentioned above. It is necessary to discuss each term for getting an idea - what actually GIS is?

Collection/Capturing 

The dataset collected for GIS may be in the form of hard copy maps, satellite images, survey data or other data obtained from other primary and secondary sources. Collection of data depends on the objective of the assignment. Data capturing involves digitization of hard copy maps and satellite images. 

Storage In GIS Storage means not merely storing whatever data we have collected. The collected data is converted in usable GIS format and then finally stored for further use either on computer hard disk or in other storage devices (CD, DVD, magnetic tapes etc.) 

Processing and Manipulation The collected and stored dataset is imported and converted into layers. Then required attributes are attached. Then data is processed for refinement, removing errors and preparing it for further GIS-based analysis. Data manipulation is essential so that it can be represented in proper understandable form. 

Analysis Analysis of GIS data is required to convert it into desired outputs. There are many type of analysis in GIS which is (or are) to be done is objective dependant. The analysis may be statistical, spatial or specialized (like network analysis, utility analysis etc. Need not to say GIS analysis requires skilled professionals. 

Management Data management is essential and very important part of GIS for storing, managing and properly maintaining GIS database. 

Retrieval In GIS, data can be retrieved through SQL or spatial queries. Some software provide tools to retrieve data by simply selecting the features. Retrieval is used for getting information about the features of our interest. 

Display Displaying of final output may in many forms. These may be hard copy printouts, on-screen display of maps, internet-based map display (through Internet Map Servers) or in the form of presentation (like power point).

Following is a good video explaining GIS in simple way. (Please note that this is just for learning purpose, we do not endorse any product)