1. Spatial analysis in gis
Prachi Sukumar Mehta
MG 0712
Date: 7th February, 2013
CEPT University

2. WHY analyze using gIS?
1. Visual representation of data – Human mind can comprehend
better
2. Vector data – precise, mathematical operations can be performed
3. Database – Spatial data with non-spatial attributes
4. Updatable – Easily can be modified, scaled
5. In-built functionalities

3. What kind of analysis can be made using gis?
• Map production
• Geovisulization
• Query, Measurement, Transformation
• Descriptive Summary
• Modeling

4. Cartography and map production
• Cartography is both an art and a science.
• GIS-based cartography makes it easier to
create large numbers of maps very quickly
using automated techniques once databases
and map templates have been built.
• Different type of data in different layers can
help in controlling the information that is
displayed.
• Maps can be reused and recycled. Different
datasets, obtained over a period of time can
be useful in analyzing trends.

5. geovisualization
There are four principal purposes of geovisualization:
1.Exploration: for example, to determine the general message of a
dataset is affected by inclusion or exclusion of particular data
elements.
2.Synthesis: To view to data in desired form.
3.Presentation: Enable the user to understand the representation.
4.Analysis: Support a range of methods and techniques of spatial
analysis.

6. Example of geovisualization : Cartograms
Cartograms are map transformations that distort area or distance in
the interests of some specific objective.
Linear cartogram transformation of London Underground

7. Query, measurement and transformation
• Spatial analysis can reveal things that might otherwise be invisible – it
can make what is implicit explicit.
• It helps us in situations when our eyes might otherwise deceive us.
Reveals pattern, trends and anomalies.
Queries : It makes no changes in the data.
No new data is generated. It just displays
the data in appropriate views.
Two or more views can be linked or
viewed together.

8. Measurement : Measurements on maps are various types.
•Length and Distance
•Area
•Shape
•Slope
Such measurements are tedious and inaccurate if made by hand.
Transformation : Creates new objects and attributes based on simple rules. May
also create new fields from existing fields or discrete objects. Buffering and Polygon
Overlay are examples of transformation.
Buffering
Overlay

9. Descriptive summary
• It is an attempt to summarize useful characteristics of data in one or two
statistics
• Mean, Median and Mode are widely used measures. E.g, Mean temperature in
December
• Centers are spatial equivalent of mean. Centers can be defined in several ways
like Centroids, Minimum Aggregate Travel (MAT) etc.
Centroid : Weighted average of MAT : Minimizes travel from a set of
coordinates. Minimizes sum of distances points. Found by iteration
squared.

10. Modeling
• Models allow planners to experiment with ‘what-if’ scenarios.
• Models can be used for dynamic simulation, providing decision makers
with dramatic visualizations of alternative futures.
Groundwater vulnerability model in an area of
Ohio, USA. The model combines GIS layers
representing that affect the groundwater, and
displays the results as a map of vulnerability
ratings
• Any model forecast should be accompanied by a
realistic measure of uncertainty.

11. Reference
• Geographic Information Systems and Science (2E) by Paul
A. Longley, Michael F. Goodchild, David J. Maguire, David
W. Rhind

12. Thank You