GEOSPATIAL DATA
CHAPTER 2
• Types of data
• Data Collection and data Transfer
• GIS data model
• Data process
GIS data types
Geographic Data and Information are the heart of GIS.
DATA INFORMATION
DATA
is the observation of real world
which are collected and processed to
give the meaning and turn into the
INFORMATION
Definition of data:
• Data means groups of
information that represent the qualitative or quantitative
attributes of a variable or set of variables.
• Data is refer to the collection
of organized information.
Data consist of number, words or images, particularly as measurement or observation of a set of variable.
Data are often viewed as the lowest level of
abstraction from which information and knowledge
are derived.
GIS organizes geographic data into a series of thematic layers and tables.
GIS links the location to each layer to give a better understanding of how the features interrelate.
In GIS, collections of geographic
features are organized into
datasets, such as land parcels, fire
location, buildings, orthophoto
imagery and raster based digital
elevation models (DEMs)
GIS data types
GIS/GEOSPATIAL DATA
SPATIAL DATA
ATTRIBUTE DATA
VECTOR
DATA RASTER
DATA
QUALITATIVE QUANTITATIVE
GIS DATA SOURCES
• GPS
• Survey Work
• Satellite data
• Existing data
• Report, table,
• Census
• Relevant department and agency
data used in GIS – Geospatial Data
There are 2 basic geospatial data types representing the real world:
Spatial data
Attribute data
The data input process is the operation
of encoding both types of data into the GIS database formats.
GIS data types
GIS data types
Spatial data format
Spatial data occupies geographic space. It usually has specific location according to some world geographic coordinate system (such as Latitude-Longitude) or address
system.
Spatial data describes the locations and geometry of spatial features.
Everything related to
everything else, but near things are more related than distant
things. (1970)
Tobler’s First
Law
GIS data types
Attribute data format
Attribute data describe the characteristics of spatial features.
These characteristics can be quantitative and/qualitative in nature.
Attribute data is often referred to as tabular data.
Spatial Data • Attribute data
GIS data types
The real world data is classified into three (3) components:
a) Location of objects (spatial component) b) Characteristic of the object (attribute component)
c) Spatial relationship between objects
TAMAN SENTOSA Bungalow (X,Y)
Owner: Maya Karin Type: FreeHold &
Double-Storey
Attribute component
Spatial component
Data Collection and data Transfer
Data collection is a data that has been obtained from the data sources which the data will include of format and projection.
Time consuming and expensive.
Data collection consists of two type of data.
i. Data Capture (direct data input)
ii. Data transfer (input of data from other systems)
Primary data sources are those collected in digital format specifically for use in a GIS project
Secondary data sources are digital and analog
datasets that were originally captured for another
purpose and need to be converted into a suitable
digital format for use in a GIS project.
DATA COLLECTION WORKFLOW
Planning
Digitizing/
Transfer Preparation
Editing/
Improvement Evaluation
CONT...
PLANNING
Important to any project and data collection is no exception.
It includes establishing user requirement, identify resources (staff, hardware and software) and developing a project
plan.
PREPARATION
Involves many tasks such as obtaining data, redrafting poor
quality map sources, editing scanned map images, removing
noise and setting up appropriate GIS hardware and software
systems to accept data.
CONT...
DIGITIZING/TRANSFER
Digitizing and transfer are the stages where the majority of the effort will be expended.
EDITING / IMPROVEMENT
Editing and improvement covers many techniques designed to validate data, as well as correct errors and improve quality.
EVALUATION
Evaluation is the process of identifying project successes and failure.
These may be qualitative or quantitative.
DATA TRANSFER
DEFINITION
How to transfer from one format to another format.
Involve with obtaining data from external sources.
Involve on how to transfer data capture by other.
Spatial data transfer standard (SDTS)
METHOD OF DATA CAPTURE IN GIS
Primary Data
• Primary data is a data that collected directly from the field.
• It is consists of both raster and vector data sources.
• In raster primary data, it is include the measurement of remote sensing and photogrammetric.
• In vector primary data, it is include the GPS and survey in measurement.
Secondary Data
• indirectly observation from other sources.
• Consists of both raster and vector data sources.
• raster secondary data - include scanned map, photograph and digital elevation model (DEM).
• vector secondary data - include topographic map and digitizing.
Data Collection
Data Transfer Data Capture
Primary Data Secondary Data
Raster Data Vector Data
Topographic surveys Scanned maps
Secondary
GPS
measurements Digital remote
sensing images Primary
Digitized data DEMs from maps
Survey
measurements Digital aerial
photographs
Vector Raster
Sources
RASTER PRIMARY DATA CAPTURE
Remote Sensing
Digital Aerial Photograph
Spatial Data Sources (Malaysia)
JUPEM
MACRES
Forestry Agency
Agriculture Department
Geology Department
JPS
State Department
Attributes data sources (Malaysia)
Town Planning Department
Health Department
Related Organization (MAKNA, etc...)
Police Department (service area)
Existing data – statistic record
etc..
GIS Data Model
GIS data structures/models
A GIS stores information about the world as a collection of thematic layers that can be linked together by geography.
This simple but extremely powerful and versatile
concept has proven invaluable for solving many real- world problems from tracking delivery vehicles, to recording details of planning applications, to
modeling global atmospheric circulation.
The thematic layer approach allows us to organize the complexity of the real world into a simple
representation to help facilitate our understanding of natural relationships.
GIS data model is grouped as
Raster data model
Vector data model
DATA MODEL in GIS
Data Model
Define how the spatial features are represents in GIS
Two types of data model
a. Raster
b. Vector
Raster and Vector
2 basic spatial data models exist
vector: based on geometry of
points
lines
Polygons
raster: based on geometry of
grid cells (images, bitmaps, DEMs
Vector model
Raster model
VECTOR DATA MODEL...
Representing Discrete features.
Represent the spatial features of points, lines and area/polygons.
Points are located by coordinates.
Lines are described by a series of connecting vectors (line segments described by the coordinates of the start of the vector, its direction, and magnitude or length).
Areas or Polygons are described by a series of vectors
enclosing the area.
Vector Data Model
Attempts to represent objects as exactly and precisely as possible by storing points, lines
(arcs) and polygons (areas) in a continuous co-ordinate space.
Data are associated with points, lines, or boundaries enclosing areas
Lines are described by a series of connecting vectors (line segments described by the
coordinates of the start of the vector, its direction, and magnitude or length).
Areas or polygons are described by a series
of vectors enclosing the area.
CONT...
Point
Line
Area/Polygon
CONT...
Vector Data Model
The vector data model use geometric objects of point, line and areas to represent the simple spatial features.
Points
Has ‘0’ dimension and has only properties of location.
A point may also defined by node, vertex or ‘0’ cell
e.g. Wells, benchmarks, utility post, man hole.
the points may have attributes.
• Utility Poles – Owner – Height – location
• Accident points – number of
accidents
– numbers of victims – Attachments
Lamp Poles
Vector Data Model
LINES
• HAS 1 DIMENSION AND HAS THE PROPERTY OF LENGTH.
• A LINE HAS TWO END POINTS AND POINTS IN BETWEEN TO MARK THE SHAPE OF LINE.
• THE SHAPE OF LINE MAYBE A SMOOTH CURVE OR SEGMENTS.
• ROADS, STREAMS, CONTOUR LINES
• road
– road name – width, length – location
– road id
• River
– river name – depth
– location
Roads centerlines
Vector Data Model
Polygon/Area
2 Dimensional and has the properties of an area (size) and perimeter.
made of connected lines.
An area may be alone or share boundaries with other areas.
An areas may contain holes.
The existence of holes mean that the areas contains both of internal and external boundaries.
An area features is made of polygons.
Land parcels (id number, owner, areas, address), water bodies, crops boundaries ( crop types, areas, owner), flood zone, buildings...
Polygons
Vector data
Vector Data Model
Node
- Can be point by itself.
- Exist at the ends of a link that connect two nodes.
Link
- Consists of single or multiple line segments
Polygon
- Link or several links formed an enclose area.
LINK POLYGON
NODE
Vector data sources
digitized features from maps
contour lines
ready digitized features – roads, land parcels and commercial buildings
Any data converted from raster format
digital topographic maps
digital road maps
existing digital data provided by any
related agencies:-, MaCGDI
RASTER DATA MODEL
Representing continuous features.
Uses a grid and grid cell to represent the spatial variation of a features.
Data are divided into cell, or pixels.
Cells are organized in arrays
Each cell has a single value
CONT
Consists of row and column format that each row and column has a individually value.
Perhaps the most common example of raster data is a digital image.
Data is stored in various formats, from a standard file based structure (Tiff, Jpeg, etc) to the binary large object (BLOB) data which stored directly in a
relational database management system (RDBMS)
CONT...
Point Line
Area/Polygon
Raster Data Sources
Satellite Imagery
Aerial Photos
Scanned Maps
Raster or Vector?
Any feature type can be represented using either raster or vector depends on its structure.
features, such as customer locations, pole locations, linear segments such roads, river, and data
summarized by area, such as postal code areas or lakes; are usually represented using the vector model.
Continuous categories, such as soil type, rainfall, or elevation, are usually represented using the raster model.
RASTER VS VECTOR
The following diagram reflects the two spatial data encoding techniques.
vector and raster models - represent the real world
Raster and Vector Data Model
Raster Data Model Vector Data Model
Raster data models
incorporate the use of a grid- cell data structure where the geographic area is divided into cells identified by row and column
Cell stored numeric values
Attempts to represent objects as exactly and precisely as possible by storing points, lines (arcs) and polygons (areas) in a continuous co-ordinate space.
Data are associated with points, lines, or boundaries enclosing areas
Raster Data Vector Data
Advantages and Disadvantages
Data Model Vector Model Raster Model
Advantages
Good representation of entity data
Compact data structure
Topology can be described in a network
Coordinates transformation is easy.
Accurate graphics
Updating and generalization is possible
Simple data structure
Easy overlay
Various kinds of spatial analysis and filtering
Uniform size and shape
Low cost (for raster image map)
Many form of data is available
Disadvantages
Complex data structures
Combining by several polygon networks is difficult, uses
considerable computer power.
Display and plotting often time consuming and expensive
Some spatial analysis is difficult or impossible to perform
Large data
Projection transformation is difficult
Different scales between layers can be difficult
May lose information due to generalization (exp: pixel generalization in landuse)
group activity….
In a group, discuss one (1) application in GIS on the following requirements:-
1- types of data
spatial vs attribute
Raster vs vector
2. Sources of data
