GE30180 Applying GIS Developing GIS Solutions

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GE30180Applying GISDeveloping GIS Solutions
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New MSc in GISc

• If you are enjoying GIS, consider a further
  degree in the area
• Its a very employable field worldwide
• Contact me if you are interested
• John.lindsay_at_manchester.ac.uk

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Readings

• Eastman, R. (2001) The Evolution of Modeling
  Tools in GIS, available online at
• http//www.directionsmag.com/article.php?article_
  id114trv1
• Lo CP and Yeung AKW. 2002. Chapter 11 GIS
  Implementation and Project Management in Concepts
  and techniques of geographic information systems

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• There is a debate about whether GISc is a genuine
  sub-discipline of Geography or simply a tool.
• This is an academic debate, and has little
  relevance for you
• Most of you are simply concerned about finding a
  job after this degree

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GIS provides a rich opportunity to find
employment after your degree
Increasingly, employers want people that are not
just GIS users, but are GIS developers
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• GIS users are limited to the functionality that
  is available through the standard GUI.
• GIS developers can enhance GIS functionality.
  They get the GIS to do what they want it to!

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Button-pushing, black-box GIS users

• We use GIS to solve spatial problems, but what if
  our particular problem cant be solved by
  pressing a button?
• GIS programming allows you to manipulate/analyse
  spatial data at a very basic level.
• GIS programmers see the algorithm and the data
  white-box GIS!
• This is very powerful for spatial analysis.

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Why program GIS?

• Create custom GIS interfaces for special purposes
• Automate repetitive or iterative tasks
• Automate complex spatial modelling
• Add functionality
• For Monte-Carlo simulation (involves random
  processes and many iteration)

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Example Tasks

• Reproject 100 shapefiles from Lat/Long to UTM
  coordinates.
• Build a simplified map interface for use by land
  managers with customized features.
• Include a map in an EXCEL spreadsheet.
• Model the error involved in extracting stream
  networks from DEMs.

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Developments in GIS Programming

• Macro-scripting languages (e.g. Arc/Infos AML,
  IDRISIs IML, TASs RCS)
• Sequence of command-line statements calling
  functions
• Some allow variables and control structures (e.g.
  loops)
• Tend to be system specific
• Can be tedious to construct and debug

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TAS script
Uncertainty in mapped streams
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Developments in GIS Programming

• Calculator Programs
• Immediately familiar and easy to use
• Allow complex equations
• Can usually save expressions and run multi-line
  expressions
• Some (not all) are limited in functionality

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ArcGIS
TAS GIS
IDRISI
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Developments in GIS Programming

• Graphical Modellers
• Flowchart story of operations
• Allows for rapid sharing of models among users

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ArcGISs ModelBuilder
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IDRISIs Macro Modeller allows dynamic modelling
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Developments in GIS Programming

• A very recent trend in GIS is to adopt the
  Component Object Model (COM).
• COM describes the way that software components
  communicate and it is independent of the
  programming language.
• COM servers (e.g. ArcGIS) expose some of their
  functionality to other applications.

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Developments in GIS Programming

• Thus it is possible to use VB, VBA, VC, Delphi
  to write programs to control the GIS like a
  puppet.
• Examples include ArcObjects and IDRISI32s API.

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GIS and Programming Languages

• ArcView used AVENUE
• Object-oriented
• Used only in ArcView
• ArcGIS uses VB (VBA) and Python
• You could use any Object-Oriented Programming
  (OOP) language, e.g. C, C, Java, etc.

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Scale of Development

• (Calculator expression)
• Script or model
• Custom GUI
• Extension
• Stand-alone application

Increasing complexity and investment
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Getting Help
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ArcGIS help function is very useful
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ArcScripts is a useful online resource
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Take a 10 minute breather
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Programming Basics
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Object-oriented Programming

• A way of developing programs that can be more
  easily re-used.
• Often used for graphical interfaces
• Common object oriented languages include
• JAVA
• C
• Python
• Visual Basic

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Principles of Object-Oriented Programming

• CLASSES include
• PROPERTIES
• The data communicated to and from the class
• METHODS
• Actions that can be taken including
• Getting or setting properties
• Performing actions on data based on the properties

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Principles of Object-Oriented Programming

• The CLASS TVset
• Properties
• Channel
• Methods
• GetChannel reports current channel
• SetChannel sets channel to designated number
• Note the CLASS TVset defines the characteristics
  of TV sets in general and not any particular TV
  set.

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Principles of Object-Oriented Programming

• Classes
• Lives in code
• Its code to control how objects work
• Objects
• An instance of a Class
• Lives in memory
• The methods and properties defined by the class
  are available in an instance of the class (i.e.
  an object)

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VB6 vs. VBA vs. VB.NET

• VB6 is and older and much used language
• The VBA language is a sub-set of VB6
• VB.NET and VB2005 are more recent and have been
  significantly modified

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Variables start with a letter, can contain
numbers, letters, underscore characters
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Public vegname as String Private area, perimeter
as Double
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Subroutines
. . . Call DoSomething () . .
Public Sub DoSomething() . . . End Sub
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Subroutines vs. Functions
Public Sub square() Dim x As Single x 3
x2 square(x) MsgBox (x2) End Sub
Public Function square(a As Single) As Double
'take input and square it square a a End
Function
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If-Then-Else Decisions
If DoesFileExist(FileName) TRUE then Kill
FileName End If OR If DoesFileExist(FileName)
TRUE then Kill FileName Else MsgBox File
does not exist,vbOKonly End If
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Select Decisions
DIM a as Integer a CInt(textbox1.text) Select
Case a Case 1 Msgbox You typed 1.,
vbOKonly Case 2 Msgbox You typed 2.,
vbOKonly Case 3 Msgbox You typed 3.,
vbOKonly Case Else Msgbox You typed a
high number.,_ vbOKonly End Select
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The For Loop
DIM a, b as Integer For a 1 to 10 Step 1 b
b 1 Next a
Nested For Loops
For Row 1 to TotalRow Step 1 For Col 1 to
TotalCol Step 1 Array1(Col, Row)
Array2(Col, Row) Next Col Next Row
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The Do Loop
Do While Until condition
statements Loop OR Do statements Loop
While Until condition
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The Do Loop
DIM a as Integer a 1 Do While a lt 100 a a
1 Loop Do a a - 1 Loop Until a 50
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Getting help

• Microsoft Developers Network (MSDN)
• Contains a wealth of information on the MS visual
  programming languages (VB, VBA, C, C, Java).
• Has tutorials and examples.
• Several good books on VB and other programming
  languages are available in the library.

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Your GIS Solution

• 25 of your final grade will be based on a GIS
  solution.
• Must involve one or more of the development
  approaches that we have discussed.
• Must be more than a simple calculator expression
  and likely less than a full extension (unless
  youre really ambitious!)
• Related to one of the three application areas
• Social Exclusion
• Air Quality Management
• Terrain Analysis

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Your GIS Solution

• 500 words description of your solution including
• What it was intended to achieve
• How you developed it
• What some of the difficulties that you ran into
  were
• A sample of the results of your solution

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Your GIS Solution

• You need not replicate the entire analysis of the
  practical exercise.
• It could focus on automating one part of the
  analysis, or it could extend the analysis beyond
  that directly covered in the practical.
• e.g. you could write a script to automatically
  evaluate the performance of fire tower heights
  and locations.

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Your GIS Solution

• You will be assessed on
• Clarity of objectives
• Appropriateness of your approach to the GIS
  solution
• Completeness
• Initiative
• Originality

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Thats it for now!

• Ill see you next week in the computer cluster.