data - analysis and modelling concepts.ppt

Data retrieval
Data retrieval involves the capability to easily
select data for graphic or attribute editing,
updating, querying, analysis and/or display.

Query
Querying is the capability to retrieve data, usually a
data subset, based on some user defined formula.
These data subsets are often referred to as logical
views.
Often the querying is closely linked to the data
manipulation and analysis subsystem
Many GIS software offerings have attempted to
standardize their querying capability by use of a
Standard Query Language (SQL).

Data Analysis
GIS – point or polygon or line layer – created –
database.
Fig 4.8 – landuse map – area with two landuse
types 1 & 2.
Recoding – possible in GIS.
Recode option used – same types are merged –
reflected in the polygon map.

Landuse Map & Recoded
Landuse Map

Soil Map with Landuse Map
Landuse map – consists 5 polygons with three
polygons – ID No.1.
Two polygons with ID No.2.

Soil Map Clipped with Landuse
Map
Clipping – Clip theme – shows the polygon Ids of
landuse.

Proximity Analysis
Natural objects – man made objects –
neighbourhood relationship.
State highway connected with national highway.
Lower order stream – connected with higher
order stream – known as Connectivity.
Traffic density – accident analysis link – state
highway with national highway is considered.
Watershed study, connection of lower order
stream with higher order is important.
Water flow from lower order to higher order
stream (fig 4.15).

Advanced Analysis
1. Network Analysis
2. Spatial Analysis
3. 3D Analysis
4. Modeling

Network Analysis
Network consists of well connected linear features.
Roads, railway line, water distribution system,
sewer line, streams are examples of networks.
Network consists – nodes & arcs with designated
direction – connection with other linear features.
Networks – topology based – attributes – flow of
objects like – traffic.
Road network – considered – explaining network
analysis.

Network Analysis
Road map – digitised with nodes & arcs.
Signals, accidents – represented as points.
Road – represented as line & two or more roads
intersect at nodes.
Dynamic model – used for network analysis.
In road network analysis, attributes for travel
time, one way street, two way street, right turn –
added – nodes & arcs.
Link – line running between two nodes.

Network Analysis
Link impendence - cost of passing through the link.
Travel time - different in links – cities – varying
traffic – different locations.
One way, closed roads, two ways, overpass,
underpass – road network – effective analysis.
Two road intersects – node is created.
Overpass passing – above a road – no node is present.
Under pass passing – below a road – do not have a
node.

 Topology
 Contiguity function
 Proximity function
 Connectivity
 Adjacency
 Time and GIS data

Spatial Analyst
extension
 Most of the functions in the Spatial Analyst Tools
are also integrated into the Spatial Analyst
extension

Types of spatial analysis
(1)
 Mapping distance
- Straight line (or Euclidean) distance
- Cost Weighted Distance
 Mapping density
 Interpolating to raster
- Inverse Distance Weighted
- Spline
- Kriging
 Performing surface analysis
- Contour
- Slop
- Aspect
- Hillshade
- Viewshed
- cut/fill

Types of spatial analysis
(2)
 Statistics
- Cell statistics
- Neighborhood statistics
- Zonal statistics
 Reclassification
 Raster Calculator (map algebra)
 Conversion of vector and raster

Spatial Analysis
1. RASTER SIMPLE ANALYSIS:
 Maps consists of numbers – two maps are –
added, divided, subtracted & multiplied.
 Fig 6.2 shows the different simple overlay.

Spatial Analysis
2. WEIGHTED OVERLAY:
 It is required in many cases.
 Landslides – occur in a location – many causes.
 Rainfall, slope, drainage, soil type, landuse –
some of the factors.
 All are not equally responsible.
 Rainfall – major criteria for landslide – after that
slope – important.
 Influence of a theme – the theme is ranked.

Spatial Analysis
3. SPREAD FUNCTION:
DEM & flood map – available for a dam area –
volume of water available.
Area inundated by flood is found.
4. SEEK FUNCTION:
DEM map – available for terrain – drainage
created.
Strahler’s stream orders – found after – drainage
is created.

Overlay
1. Boolean or Logical Overlay
2. Intersect Overlay
3. Point in Polygon Overlay
4. Line in Polygon Overlay
5. Union Overlay

Boolean Overlay
They are AND, OR, NOT & XOR.
Used to extract information based on the overlay.

Principles of GIS Modeling
What is GIS Modeling?
The process of creating new GIS products from
existing products is known as “GIS Modeling”.
Typically this is not “modeling” as in a simulation
model or a statistical model – although it can be….

Tools for GIS Modeling
“Modelbuilder” model

Tools for GIS Modeling
2. Programming Languages
 Use programming languages such as
Python, C++, JAVA, or Visual Basic
Most flexible – but also most difficult!

GIS Modeling Approaches
Before you choose a modeling tool and start to
work, there are a number of steps you should go
through.
The first, and most critical, is to determine what
the OUTPUT of the modeling process should be,
i) You can’t go on a journey without
first identifying your destination!
ii) The “trip” can be a short one, or a long
complicated one!

Planning your model
Often your model will be complicated with
several different intermediate data layers.
Even if ultimately you want to do an automated
modeling process,
It is a good idea to step through the process
manually,
Studying each intermediate data layer as you go
along.

Tests of a model
One or more variables are predicted
–from inputs
–at one point in time
•Universal Soil Loss Equation
•Spatial Interaction Model
–dynamically
•urban growth models

Test of model
Spatially disaggregated
–inputs or outputs
–two or more elements
Not invariant under relocation

Types of model
Conceptual
–boxes and arrows
–rules
Mathematical
–partial differential equation
Numerical
–finite difference approximation
–scale-dependent
Computational
–code

GIS and modeling
Using GIS to prepare data, display results
–loosely coupled to modeling code
Model and GIS working off the same database
–component-based software architecture
–tight coupling
Writing the model in the GIS's scripting language
–embedding
–performance problems for dynamic models

Terrain mapping
 DEM
 TIN
 THIESSEN POLYGONS

DEM (Digital Elevation
Model)
DEM – obtained from contours.
Contours only – lines – have elevation.
After interpolation – each & every location –
consist an elevation.
USGS supplies DEM data – but it is different from
the DEM obtained – using interpolation – in GIS
software.

Interpolation
Assumed – no significant error – in sampling –
points are well distributed.
Pattern changes in regular manner.
Thiessen polygon – type of interpolation.
All changes – taken into account.
This is like stepped terrace.
Changes – taking place – edge of the polygons.

DTM
(digital terrain model)
A term which is commonly used interchangeably
with DEM.
Strictly speaking a DTM refers to a model of reality
which includes information relating to factors such
as surface texture as well as elevation.
Digital terrain models are representations of land
surface point elevations.

DTM
(digital terrain model)
The DTM data points were collected on analytical
stereoplotters at a sufficient density to support
generation of 3-meter contours conforming to the
National Map Accuracy Standards (+ or - 1.5
meters).
These DTMs are stored in ASCII text format.

3D GIS
In comparison to the advancements in 3D
visualization, relatively little has been
accomplished in the realization of a practical 3D
GIS.
A 3D GIS, on the other hand, deals with volumes.
3D GIS requires this information to be complete
and continuous.
Once the data is collected, a raster or vector 3D
data structure must be chosen to describe geo-
objects.

Road 3d - gis
Roads 3D-GIS is targeted to improve the decision
making process encountered by transportation
authorities.
The software provides GIS capabilities and
information in a realistic 3D environment.

ADVANTAGES OF ROAD 3D –
GIS
ADVANTAGES OF ROAD 3D – GIS:
Decision Making Process – from pre-design
stages to implementation approval committees.
Landscape integration – thorough assessment of
road landscape integration.
Infrastructure Coordination – avoiding the
most common design flaw as a result of
asynchronous information.

ADVANTAGES OF ROAD 3D –
GIS
Safety Audits – assure that roads include well-
designed intersections, road surfaces, visibility and
traffic control devices while still in design stages.
Work efficiency – full / semi automated standards
compliance evaluation.

Artificial intelligence
A branch of computer science that aims to
simulate the thought process of the human brain,
commonly through the use of software.
Pattern Recognition is a major application field
for various aspects of Artificial Intelligence .
From the early nineties the concept of intelligent
agents has got growing importance in the field of
artificial intelligence

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