GIS Basics
GIS Basics
Tutorial 1
Theoretical
Tutorial 1
Theoretical
In this tutorial we will cover basic concepts about GIS to build our knowledge in this technology that will serve as a foundation in studying GIS and applying it for various analysis. Let us begin with by answering the question
"What is GIS?"
"GIS" stands for Geographic Information System which consists of three integrated elements;
Geographic from geography: The real world elements (living and non living) both natural and man made, e.g., roads, houses, canals, rivers, human population, plants, wildlife etc.
Information: Knowledge obtained from investigation and research and presented in a form which has meaning and use, e.g., human population of a country, length of a road, number of plant species in environment etc. In the GIS, normally we call it "Data".
System: Converting this information or Data into meaningful easily understandable presentation; computer technology and its supportive infrastructure both in the form of a software and hardware is used in GIS.
In the GIS we present everything in the form of a map whether it is a simple population map of country or a more complex web base GIS platform e.g., google maps showing different information such as route planning, location of restaurants etc. So basic understanding of a "map" is very important.
The real world is 3D (3-Dimensional) and we represent it in the form of 2D (2-Dimensional) on paper and this representation is called as "Map". A map by definition is a general description of the reality outlining it in the form of points, lines and polygons etc. Simply we can say that, "A map is a 2D Model of reality". Terrain or topography of an area on earth can be represented on map using iso-lines or contours for different elevations. A map must have the following descriptions;
Since map is a 2D model of reality that is being developed by utilizing information which has meaning and use and this information we call in GIS as geographical data or sometime referred as geometrical data. This geometrical data basically consists of data which has location information or in GIS we say it spatial information/spatial structure.
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We represent this geographical data in GIS in three different types;
1. Point Objects (e.g., wells, drilling holes, bus stops, etc)
2. Lines (e.g., roads, water courses, rivers, canals, country borders etc)
3. Polygons (e.g., lakes, buildings, land use, etc)
Every object in our surroundings can be represented on a map in GIS using these three basic geometrical object types. Points, lines and polygons are used to represent most objects in our environment which have defined spatial delimitation but in our physical environment some of the geographical data have no specific spatial delimitation e.g., precipitation, temperature, topography etc., Therefore these kind of data represented as continuous surface on a map. Geographical data in GIS either in the form of a geometrical data or represented as a continuous surface on a map must have information linked to it. For example, a line object representing a road can have information describing its length, speed limit, number of lanes on the road etc. This information is called as Attribute Data. In the early days of GIS technology, tables was used to represent the attribute data but today with the advancement in GIS technology, any type of digital information such as tables, texts, video, audio, images etc. can be linked to the geographical data.
In the GIS we need a link to connect geographical data with attribute data. This connecting link tells the computer to recognize
In the GIS, we have two divided the geographical data into two major categories;
1. Vector Data
The geographical data consisting of geometrical elements such as lines, polygons and points having location information is called as vector data.
2. Raster Data
Geographic from geography: The real world elements (living and non living) both natural and man made, e.g., roads, houses, canals, rivers, human population, plants, wildlife etc.
Information: Knowledge obtained from investigation and research and presented in a form which has meaning and use, e.g., human population of a country, length of a road, number of plant species in environment etc. In the GIS, normally we call it "Data".
System: Converting this information or Data into meaningful easily understandable presentation; computer technology and its supportive infrastructure both in the form of a software and hardware is used in GIS.
In the GIS we present everything in the form of a map whether it is a simple population map of country or a more complex web base GIS platform e.g., google maps showing different information such as route planning, location of restaurants etc. So basic understanding of a "map" is very important.
The real world is 3D (3-Dimensional) and we represent it in the form of 2D (2-Dimensional) on paper and this representation is called as "Map". A map by definition is a general description of the reality outlining it in the form of points, lines and polygons etc. Simply we can say that, "A map is a 2D Model of reality". Terrain or topography of an area on earth can be represented on map using iso-lines or contours for different elevations. A map must have the following descriptions;
- Title
- Legend
- Scale
- A sign showing the North
- Projection
Since map is a 2D model of reality that is being developed by utilizing information which has meaning and use and this information we call in GIS as geographical data or sometime referred as geometrical data. This geometrical data basically consists of data which has location information or in GIS we say it spatial information/spatial structure.
We represent this geographical data in GIS in three different types;
1. Point Objects (e.g., wells, drilling holes, bus stops, etc)
2. Lines (e.g., roads, water courses, rivers, canals, country borders etc)
3. Polygons (e.g., lakes, buildings, land use, etc)
Every object in our surroundings can be represented on a map in GIS using these three basic geometrical object types. Points, lines and polygons are used to represent most objects in our environment which have defined spatial delimitation but in our physical environment some of the geographical data have no specific spatial delimitation e.g., precipitation, temperature, topography etc., Therefore these kind of data represented as continuous surface on a map. Geographical data in GIS either in the form of a geometrical data or represented as a continuous surface on a map must have information linked to it. For example, a line object representing a road can have information describing its length, speed limit, number of lanes on the road etc. This information is called as Attribute Data. In the early days of GIS technology, tables was used to represent the attribute data but today with the advancement in GIS technology, any type of digital information such as tables, texts, video, audio, images etc. can be linked to the geographical data.
In the GIS we need a link to connect geographical data with attribute data. This connecting link tells the computer to recognize
In the GIS, we have two divided the geographical data into two major categories;
1. Vector Data
The geographical data consisting of geometrical elements such as lines, polygons and points having location information is called as vector data.
2. Raster Data