Geographic information system
GIS
Geographical information system (GIS)
A computer application that helps us to access and use
geographical information.
It helps us to access and use information such as
information about drainage, settlement, land uses and
relief.
Remote sensing
This is the collecting of information about objects from a
vertical distance.
It involves using aero planes, drones, hot air balloons and
satellites to collect information about objects.
Advantages of remote sensing.
It is cheap
It can be used in places that are difficult to access by
people like mountains
It is time saving
Vector and raster data
Vector data
This is Data represented in form of points, lines and
polygons or areas.
Topographic maps are made up of vector data.
Features are inform of points, lines or polygons
Point features- settlements, spot heights, trigonometrical
stations, police station
Line features- rivers, roads
Polygon features- dams, lakes, cultivated land
Raster data
This is Data represented inform of digital images.
Orthophoto maps are an example of raster data
Pixels
These are the smallest building blocks of digital images or
the smallest unit of raster data
The higher the pixel image, the more clear the image
Spatial resolution
This is the amount of detail shown in a digital image
It refers to how clear a digital image is
High spatial resolution- images that show a lot of details
Images that are very clear
Low spatial resolution- images that show less details
Images that no clear
Attribute and spatial data
Attribute data
This is data that describes the characteristics of features.
An attribute is a characteristic of a feature
Forexample,
•
It is a Periodic river
•
The river has a dendritic drainage pattern
•
The river has a high drainage density
Spatial data
This is Data that describes the location of a feature or
object
The location of a feature is described by its grid reference
Data layers
This is a set of information showing a specific theme.
Examples of data layers
Drainage of a place
Relief of a place
Settlements in a place
Data layering
This refers to the Placing of data layers on top of one
another
A topographic map is an example of data layering
Paper GIS.
Data integration
Combining different sets of data together.
Gis components
These are the different parts that make up the GIS
Examples of components
Software
Hardware
Users
Data
methods
Buffering
Demarcation of an area around a feature
Data manipulation
This is data that has been processed and converted
making it easier to use.
Querying
Ability to ask and answer questions about geographic
features and their attributes and relation between them
Data standardisation
Making data similar for analysis
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