gis functionality

8/9/2019 GIS Functionality

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GIS FUNCTIONALITYGIS FUNCTIONALITY

Data acquisitionDigitize maps & documents

Obtain existing data set

Perform primary survey

Preliminary data processingnterpret c ass y surveye ata

Structure digital data for chosen spatial model

Data storage and retrieval

By class or attribute

Spatial search and analysis

Graphical display and interaction


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Observed

phenomena

Documents

& maps

Raw data

1.Data

acquisition

Five categories of function in GIS

Graphic

s

Structured

data

Interpretatio

n

Database 2.Preliminarydata processing

3.Storage &

retrieval

4.Search &

analysis

5.Display &

interaction


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Data AcquisitionData Acquisition

Primary data Secondary data

Three modes/ dimension : Spatial, Temporal, Thematic


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The survey techniques: (primary data acquisition)ground based studies of topography, geology and

vegetation, airborne surveys using satellites, GPS andaero-planes for natural resource management.

Much of the satellite imagery used in GIS has a groundresolution of between 4 and 80 m, useful for studies ofenvironmental ariables such as egetation andhydrology.

Photogrammetric interpretation of aerial photographs,

on the other hand, can produce highly accurate datawhich, can be used for creating and updating large-scale maps, such as at 1:500 or 1:1000 scales.


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Survey

Methods:

Remote sensing

Ground survey

InterviewsBorehole logging

Raw Data:

Scanned images

Photographs

Field documents

Geophysical logs

Census data

Primary data acquisition generates raw data from survey


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Secondary data sources

Published maps in analogue form

Socio-economic survey data

Processes:

Digitizing

Coding

Scanning

Editing

Verification

Word processing

aw a a:

Vector data

Raster data

Scanned data

Text files

Attribute data

Secondary data acquisition


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Spatial dataSpatial data

Raster

Structured array or grid of cells Pixels

Represent large range of computable

spatial objectsxamp es: a e e mages, g a eva on

Model

Vector

Basic building block is point Storage space is less

Examples :Shape files, DLG (Digital line graph)Road( line) , Well (point), Urban area (polygon)


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Raster & Vector


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Generic structure for a grid

R

ows

Resolution

Columns


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Rasters are faster...

A raster or grid maps directly onto a programming

computer memory structure called an array.

Good for representing continuous surfaces.

Rasters are a natural for scanned or remotely sensed data

Rasters are easy to understand

Spatial analytical operations are faster

Compression is easier using techniques such as Run

Length Encoding and quadtrees


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Disadvantages

Rasters are poor at representing points, lines andareas

Good only at very localized topology, and weak

otherwise

Suffer from the mixed pixel problem

Must often include redundant or missing data

Each cell can be owned by only one feature

More storage space


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The Vector ModelThe Vector Model

A vector data model uses points stored by theirreal (Earth) coordinates. Lines are built fromsequences of points in order.

Lines have a direction according to the orderingof the oints.

Polygons can be built from points or lines.

Vector data model evolved into the arc/nodevariation in the 1960s

The endpoint of a line (arc) is called a node. Arcjunctions are only at nodes


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Vector Model FeaturingVector Model Featuring

Arcs and NodesArcs and Nodes


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Preliminary data processingPreliminary data processing

Purpose to create topologically structuredspatial data

To change data representation (Rasterization,

To modify classification schemes

To transform between cooridnate systems andmap projections


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Image classification


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A process of subdivision of given well

defined linear or areal object into cells.

Vector to raster (rasterization))

Easier and can be done with the help of

rasterization algorithms


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Reassembly of the pixels without prior

knowledge of what pixel belongs to what

object.

(d) Raster to Vector (vectorization)


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Surface Modeling

Interpolation


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TIN: triangulated irregular network;

irregular grid.

Triangulation


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(f) Reclassification

Use of two or more classification or coding

schemes referring to same phenomena;

Recoding; Less detailed, or generalized class:

line dropping and map dissolve.


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Change in map projection

Coordinate transformation:

original recording the real -world units of a map

projection

map grid system


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Data storage and RetrievalData storage and Retrieval

Function to create spatial database

Spatial database contain vector, raster and attribute data

GIS requires that both data and maps be

represented as numbers.

in a physical data structure (i.e. files anddirectories).

Files can be written in binary or as ASCII text.


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Maps as Numbers:Maps as Numbers:

Raters and Vectors can be flat files if theyare simple


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Maps as Numbers: Attribute DataMaps as Numbers: Attribute Data

Attribute Data arestored logically inflat files.

i.e., matrix ofnumbers and valuesstored in rows andcolumns, like aspreadsheet.

DBMSs use manydifferent methods tostore and manageflat files.


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Geodatabase modelGeodatabase model

Stores geographic coordinates as oneattribute in a relational database table

Uses MS Access for Personal

Uses Oracle, Sybase, Ingress or othercommercial relational databases forEnterprise Geodatabases (many

simultaneous users)


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ArcGIS GeodatabaseArcGIS Geodatabase

Geodatabase

Feature Dataset

Feature Class

Workspace

eometr c

Network

Object ClassRelationship


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Feature ClassFeature Class

A feature classis a collection ofgeographic objectsin tabular format

that have thesame behaviorand the same

attributes.


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Object ClassObject Class

An object class is a collectionofobjects in tabular formatthathave the same behavior and the

same attributes.


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RelationshipRelationship

A relationship is an association or linkbetween two objects in a database.

A relationship can exist between spatial

objects (features in feature classes),non-spat a o ects o ects n o ectclasses), or between spatial and non-spatial objects.


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RelationshipRelationshipRelationship between non-spatial objects

Water

Data

Water

Quality

Parameters


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Relationship between spatial and non-spatial objects

Water quality data

(non-spatial)

Measurement station

(spatial)


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Relationship between spatial objects

Rivers that lie within

California

Two spatial objects:

rivers and California


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Vectors and TopologyVectors and Topology


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Spatial search and analysis

Spatial containment search with a rectangularwindow


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Spatial containment search

based on an existing object


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Proximal search:Buffer: spread function

connectivity

similar


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Phenomenon-based search and overlay processing

Phenomenon-based search, using a single theme or class, selects spatial

objects that (a) belong to particular categories or (b) meet specified

constraints on their spatial and non-spatial attributes.


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OR

AND

XOR

Union

Intersection

=

=

=

=

=

NOT =

Difference

Difference

=

=

Boolean and set operations can be used to combine spatial regions in overlay

analysis. The region may be regarded hare as true (shaded) and false (clear).


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Relational operators Arithmeticoperators

Greater than a + b Addition

< -

Relational and Arithmetic operatorsRelational and Arithmetic operators

a = b Equals a x b multiplication

a b Greater than or equal to a b division

a

b Less than or equal to a

b

exponential a b Not equal


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Grade 3

Agricultural land

Phenomenon-based search combining themes. Regions of alluvium

geology that coincides with agricultural land of grade 3


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Overlay analysisOverlay analysis


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ANDAND

Combinations of many themes with a proximal spatial

constraint


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Spatial analysisSpatial analysis

Interpolation and surface modeling

TIN, Grid for terrain modeling

Best path analysis and routing

Shortest route based on time and costpa a n erac on mo e ng

Optimal location of sites

Correlation, association, patterns and trends

Health management


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ArcGIS has a three part interface:ArcGIS has a three part interface:

ArcCatalog for navigating spatial data

Introduction to ArcGISIntroduction to ArcGIS

ArcMap for creating presentation graphics

ArcToolbox powerful geoprocessing tools


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Data for ArcGISData for ArcGIS

Vector Data

ArcView Shapefiles

ArcInfo Coverages

Geodatabase raw ngs

Raster Data

Most common imagery formats can beread


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Image DatasetsImage Datasets

Supported image formats: ARC Digitized Raster Graphics (ADRG)

Windows bitmap images (BMP) [.bmp]

Multiband (BSQ, BIL and BIP) and single band images[.bsq, .bil and .bip]

ERDAS [.lan and .gis]

ESRI Grid datasets

IMAGINE [.img]

IMPELL Bitmaps [.rlc]

Image catalogs

JPEG [.jpg]

MrSID [.sid]

National Image Transfer Format (NITF)

Sun rasterfiles [.rs, .ras and .sun]

Tag Image File Format (TIFF) [.tiff, .tif and .tff]

TIFF/LZW


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ArcCatalog: PreviewsArcCatalog: Previews

Using ArcCatalog you can easily preview both yourspatial datasets, and the attribute data associated withthem


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Within ArcCatalog you can easily search for databased on location and attributes stored in its metadata

ArcCatalog: Spatial SearchArcCatalog: Spatial Search


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ArcCatalog: Data ManagementArcCatalog: Data Management

ArcCatalog is provides an environment where it is safe to cutand paste spatial data into new directories, and even into the

newest ESRI spatial data structure, the geodatabase.

Additionally, several common conversion routines are

available from ArcCatalog


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ArcCatalog includes tools for viewing and editing Metadata. It even has an

option to automatically update some items in the metadata whenever a

dataset is edited

ArcCatalog: MetadataArcCatalog: Metadata


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Tools Toolbar

Menu bar

Standard Toolbar

ArcMap: Map ViewArcMap: Map View

Table of ContentsCanvas

Draw Toolbar


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Map Documents (.mxd) Saves your progress inArcMap. Does not save GIS data, just references itslocation on disk.

La er Files .l r Saves s mbolo and other dis la

Saving your work in ArcGISSaving your work in ArcGIS

properties for a data source. Again, the data source itselfis not copied, but instead referenced by the layer file

Map Templates (.mxt) If you are going to createseveral maps with a similar layout, the template can be atime-saving tool.


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ArcToolboxArcToolbox For heavy duty processing, ArcToolbox contains analysis,

conversion, and data management tools. Additionally, there is

an option to construct your own custom tools. You may set up

most tools using wizards which help take the guess work out

of some of the otherwise complicated options


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33--D AnalystD Analyst

Analysis ofland surfaceterrain astriangulated

irregularnetwork (TIN)

Visualization in3-D using Arc

Scene

Stream channel of Pecan Bayou, TX


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Spatial AnalystSpatial Analyst

Analysis of landsurface terrainas a grid

defining drainageareas andconnectivity to

stream network

Drainage network for Montgomery, AL


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Grid DatasetsGrid Datasets

Cellular-based data structure composed of square

cells of equal sizearranged in rows and columns.

and columns), as well as the value at each cell have

to be stored as part of the grid definition.Number of columns

Numberofcolumns

Cell size


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Grid DatasetsGrid Datasets

Grid datasets