GEOSPATIAL DATA

CHAPTER 2

GEOSPATIAL DATA • Types of data • Data Collection Transfer • GIS data model • Data process

and

data

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.

ď ą

Data consist of number, words or images, particularly as measurement or observation of a set of variable.

ď ą

Data are often viewed as the lowest level of abstraction from which information and knowledge are derived.

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GIS organizes geographic data into a series of thematic layers and tables.

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GIS links the location to each layer to give a better understanding of how the features interrelate.

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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

VECTOR DATA

ATTRIBUTE DATA

RASTER DATA

QUALITATIVE

QUANTITATIVE

GIS DATA SOURCES •

GPS

•

Survey Work

•

Satellite data

•

Existing data

•

Report, table,

•

Census

•

Relevant department and agency

GIS data types 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 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.

Tobler’s First Law

Everything related to everything else, but near things are more related than distant things. (1970)

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

Spatial component

Attribute 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. ii.

Data Capture (direct data input) Data transfer (input of data from other systems)

ď ľPrimary data sources are those collected in digital format specifically for use in a GIS project

ď ľSecondary 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

Evaluation

Editing/ Improvement

Preparation

Digitizing/ Transfer

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 Capture

Data Transfer

Primary Data

Secondary Data

Raster Data

Vector Data

Sources

Primary

Raster

Vector

Digital remote sensing images

GPS measurements

Digital aerial photographs

Survey measurements

Scanned maps

Topographic surveys

Secondary

Digitized data DEMs from maps

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 realworld 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 ď ľ

Raster data model

ď ľ

Vector data model

DATA MODEL in GIS Data Model Define how the represents in GIS

spatial

Two types of data model a. b.

Raster Vector

features

are

Raster and Vector

2 basic spatial data models exist vector: based on geometry of

points  lines  Polygons 

Vector model

raster: based on geometry of 

grid cells (images, bitmaps, DEMs

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.

NODE

LINK

POLYGON

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 Area/Polygon Line

Raster Data Sources Aerial Photos

Satellite Imagery

Scanned Maps

Raster or Vector? ď ľ

Any feature type can be represented using either raster or vector depends on its structure.

ď ľ

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.

ď ľ

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  Attempts to represent incorporate the use of a gridobjects as exactly and cell data structure where the precisely as possible by geographic area is divided storing points, lines (arcs) into cells identified by row and polygons (areas) in a and column continuous co-ordinate  Cell stored numeric values space.  Data are associated with points, lines, or boundaries enclosing areas

Vector Data

Raster Data

Advantages and Disadvantages Data Model

Vector 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

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)

Disadvantages

Raster Model

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