This document discusses two types of spatial data used in GIS - vector data and raster data. Vector data represents geographic features as points, lines, and polygons using vertices with x, y, and z coordinates. It allows for accurate representation of shapes and storing of attribute data but requires more processing and storage. Raster data represents geographic information through a grid of cells (pixels), with each cell storing attribute values like elevation or temperature. It is better for continuously changing data but cannot represent linear features well and has increased storage needs at higher resolutions. Both data types have advantages and disadvantages depending on the use case.
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ppt spatial data
1. Vector and rastar data
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2. The data or information that identifies the
geographic location of features and
boundries.
On earth, such as natural and construted
features like Ocean, lake, pond etc.
Spatial data is usually stored as coordinate
and topology, and is data that can be
mapped.
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3. IN GIS THEARE ARE TWO BASIC
SPATIAL DATA TYPES
RASTER
DATA
VECTOR
DATA
IN GIS THERE ARE TWO TYPES OF SPATIAL
DATA TYPES
4. Vector Data
Vector data provide a way to represent real world
features within the GIS environment. A vector feature
has its shape represented using geometry. The
geometry is made up of one or more interconnected
vertices. A vertex describe a position in space using an
x, y and optionally z axis. In the vector data model,
features on the earth are represented as:
• points
• lines / routes
• polygons / regions
• TINs (triangulated irregular networks)
5. Vector Data
This system of recording features is based on the
interaction between arcs and nodes, represented by
points, lines and polygons. A point is a single node, a
line is two nodes with an arc between them, and a
polygon is a closed group of three or more arcs. With
these three elements , it is possible to record most all
necessary information.
Points Lines
Polygons
6. Vector Data
Advantages
• accurately representing true shape and size
• representing non-continuous data (e.g., rivers, political
boundaries, road lines)
• Vectors can store information
About topology
• A vector data model uses points
stored by their real (earth)
coordinates and so requires a
• precise coordinate system.
• Geographic Coordinate System
Latitude/Longitude
• Cartesian Coordinate Systems
X,Y Coordinate system
7. Vector Data
Disadvantages:
• The location of each vertex needs to be
stored explicitly.
• Vector data must be converted into a
topological structure.
• This is often processing intensive and
usually requires extensive data cleaning.
• Updating or editing of the vector data
requires re-building of the topology.
10. Raster Data
Raster Data – cell –based data such as aerial imagery
and digital elevation models. Raster data is
characterized by pixel values. Basically, a raster file is
a giant table, where each pixel is assigned a specific
value from 0 to 255. The meaning behind these values
is specified by the user – they can represent elevations,
temperature, hydrology and etc.
12. Advantages:
• Raster is the best way to store continuously changing
values such as elevation, slope.
• Analysis faster and more flexible then vector for
many application.
• Rapid computations ("map algebra") in which raster
layers are treated as elements in mathematical
expressions
14. Raster Data
Disadvantages:
• It is especially difficult to adequately represent
linear features depending on the cell resolution.
• Network linkages are difficult to establish.
• Processing of associated attribute data may be
cumbersome if large amounts of data exists.
• Raster maps inherently reflect only one attribute or
characteristic for an area.
• Most output maps from grid-cell systems do not
conform to high-quality cartographic needs.
