www'geonorth'com

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GIS and Engineering

• Mark Pearson, PE (civil)
• GeoNorth, LLC
• GIS, Database, Internet Consulting
• Anchorage, Portland
• 13 Years Old (91 DOGS Years)
• App Development, Planning, Conversion
• Huge to Tiny Projects/Organizations

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The Plan

• ArcObjects
• Concepts
• Examples
• Python
• Concepts
• Examples
• Compare/Contrast
• Discussion

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Multiple Ways to Skin the Cat
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ArcObjects Serious Programming

• AML
• Throw commands into text file and youre a
  programmer
• Avenue
• Proprietary Language

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ArcObjects

• Not a Language
• Building Blocks Upon which ArcGIS was built
• COM objects
• Most commonly used with VisualBasic or C

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ArcObjects First Rule
Whining
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VisualBasic
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Modeling the Real World

• Objects

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Object Oriented
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Object Orientation

• Properties
• Characteristics (nouns)
• Methods
• Actions object knows how to perform (verbs)
• Events
• Occurrences that Object can respond to

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Objects Vs. Classes
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Objects Vs. Classes

• Class is the Blueprint
• Object is the House
• An instantiation

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Interface vs. Objects
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Interfaces vs. Objects
Dim pFeatureLayer As IFeatureLayer Dim
pAttributeTable as IAttributeTable Set
pFeatureLayer new FeatureLayer Set
pAttributeTable pFeatureLayer Query Interface
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Tips

• Learn all of the on-line resources and use them

arcobjectsonline.esri.com
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Tips

• Use Samples
• Lots of Them
• Almost Never Start from Scratch

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Tips

• Training is Worth It for quick jump start
• We have an ArcObjects course in March (hint)

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Tips

• Spend Time on Error Handling

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ArcObjects

• For hard-core programmers Nirvana
• For casual programmers Purgatory
• Non programmers Hell

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ArcObjects Before After
Before ArcObjects
After ArcObjects
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ArcObjects

• Up Side Granularity of Control
• Down Side Nothing is Easy

For the casual user
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Common Implementations

• Quick Dirty Automation using VBA within ArcMap
• Separate stand-alone applications
• Extensions to ArcGIS framework
• Compiled DLL(s)

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Example in ArcObjects

• Example Programmatically Turn a Layer Off

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• Private Sub TurnOffLayer()
• Dim pDoc As IMxDocument
• Dim pMap As IMap
• Dim pLayer As ILayer
• Dim pActiveView As IActiveView
• Set pDoc ThisDocument
• Set pMap pDoc.FocusMap
• Set pLayer

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Private Function FindLayerByName(strLayerName As
String, pMap As IMap) As ILayer Dim i As
Integer For i 0 To pMap.LayerCount - 1
If UCase(pMap.Layer(i).Name)
UCase(strLayerName) Then Set
FindLayerByName pMap.Layer(i) Exit
Function End If Next i Set
FindLayerByName Null End Function
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• Private Sub TurnOffLayer()
• Dim pDoc As IMxDocument
• Dim pMap As IMap
• Dim pLayer As ILayer
• Dim pActiveView As IActiveView
• Set pDoc ThisDocument
• Set pMap pDoc.FocusMap
• Set pLayer FindLayerByName("parcels", pMap)
• pLayer.Visible False
• End Sub

Set pActiveView pMap this is a query
interface pActiveView.Refresh
pActiveView.ContentsChanged
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ArcObjects 8.x to 9.0

• Good News not much pain
• Binary Compatibility for most core-level
  libraries
• Not like Avenue versus ArcObjects

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Type Libraries Diced Up

• Esricore.olb was one huge library
• Now slit into functional groups

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Type Libraries Diced Up
ArcObjects 8.x
ArcObjects 9.0
Declarations Dim pEnv as esriCore.IEnvelope Dim
pEnv as esriGeometry.IEnvelope ZoomToPoint (inPt
as esricore.IPoint) ZoomToPoint(inPt As
esriGeometry.IPoint) Instantiations Set pPt
new esriCore.Point set pPt New
esriGeometry.Point Implementations Implements
esricore.ITool Implements esriFramework.ITool
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ArcGIS 9.0 Type Libraries

• ArcGIS Engine UI
• esriSystemUI
• esriDisplayUI
• esriOutputUI
• esriGeoDatabaseUI
• esriDataSourcesRasterUI
• esriLocationUI
• esriCartoUI
• esriCadUI
• esriIMSUI
• esriTinUI
• esriCatalogUI
• ArcGIS Application assemblies
• esriArcMapUI
• esriArcMap
• esriArcCatalogUI
• esriArcCatalog
• esriEditor

ArcGIS Engine esriSystem esriGeometry esriDisplay
esriOutput esriGeoDatabase esriDataSourcesFile esr
iDataSourcesGDB esriDataSourcesOleDB esriDataSourc
esRaster esriGeoDatabaseDistributed esriLocation e
sriCarto esriCad esriIMS esriTin esriWorker
esriFramework
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Code Converter Utility

• VB6 Add-In
• Removes ESRI Object Library from Project
  reference
• Replaces esriCore. with appropriate name in
• Declarations
• Instantiations
• Implementations
• ProgIDs
• Adds appropriate new references according code
  that is found

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Tips for Healthy ArcObjects Use

• Never over promise amount of time
• Always plagiarize Code
• ArcObjects Online / Samples
• Knowledgebase
• Your own code
• Keep a Toolbox of common routines
• Make subs/functions generic whenever you can

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• Python/Scripting

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Scripting in ArcGIS

• Python
• VBScript
• Perl
• Jscript
• Any scripting language that is COM compliant
• Python is ESRI-prefered

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Why Python?

• Easy to learn, clean, clear syntax
• Supports Object Oriented programming
• Works well with complicated data structures
• Simple to integrate with C and Fortram
• Can be seamlessly integrated with Java
• Free, Open Source, Widely Used

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Python

• Not invented by ESRI
• Interpreted, interactive, object-oriented
• Invented in 1991 by Guido von Rossum, Netherlands
• Named after Monty Python
• www.python.org
• Platforms Windows, all UNIX, OS/2, Mac, Amiga
  even Nokia cell phones

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Geoprocessing with Python

• Geoprocessor Programming Model

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Scripts in ArcToolBox
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Importing Modules

• Python scripts are Modules
• Use the import statement to load and use
  modules
• All geoprocessing scripts use the win32com
  module
• Supports communciation between Python and the COM
  IDispatch interface, which is used by the
  geoprocessor
• Other modules to math, file I/O, OS stuff, etc.

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Standard Stuff at in a Python Script

• import win32com.client, sys, os
• sys is python system, user input, etc.
• Os does OS-specific file manipulation
• Create the Geoprocessor object
• GP win32com.client.Dispatch("esriGeoprocessing.G
  pDispatch.1")
• Declares and creates geoprocessing object that
  you will use later
• Set the input workspace
• GP.workspace c\data\anchorage\shapes
• GP.workspace sys.argv1

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Indentation and Spaces

• They are relevant!
• try
• get a list of featureclasses in workspace
• fcs GP.ListFeatureClasses()
• Python is also case sensitive !!!
• gp is not the same as GP

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Batch Processing

• ListDatasets (Wild Card, Dataset Type)
• ListFeatureClasses (Wild Card, Feature Type)
• ListFields (Input Value, Wild Card, Field Type)
• ListIndexes (Input Value, Wild Card)
• ListRasters (Wild Card, Raster Type)
• ListTables (Wild Card, Table Type)
• ListWorkspaces (Wild Card, Workspace Type)
• All return an Enumeration (list with unknown
  count)

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Batch Example

• Import COM Dispatch module
• from win32com.client import Dispatch
• Create the geoprocessor object
• GP Dispatch("esriGeoprocessing.GPDispatch.1")
• Set the workspace. List all of the feature
  classes that start with 'G'
• GP.Workspace c/data/anchorage/anch.mdb
• fcs GP.ListFeatureClasses("G")
• or for a type fcs GP.ListFeatureClasses("G",
  "polygon")

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Batch Example

• Reset the enumeration to make sure the first
  object is returned
• fcs.reset()
• Get the first feature class name
• fc fcs.next()
• while fc While the feature class name is not
  None
• Copy the features from the workspace to a
  folder
• GP.Copy(fc,c\data\anchorage\dataout\
  fc)
• Get the next feature class name
• fc fcs.next()

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Licensing

• When a tool is executed, either thru the
  ArcToolbox or thru Script, an ArcGIS Desktop
  license is required
• Extension Licenses, too

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Extending Python with Wrappers

• Vector Formats
• pyshapelib (shapelib.maptools.org)
• Access to individual vertices of the shape
• Dbf file
• Indexing
• OGR (gdal.maptools.org/ogr)
• Other vector formats like MapInfo, Coverage,
  PostGIS, Oracle Spatial, TIGER, SDTS, OpeNDAP,
  DGN, Microstation DGN

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Extending Python with Wrappers

• Grids
• Geodata Abstration Library GDAL
  (gdal.maptools.org)
• JPEG2000, BSP, USGS DEM, Military
• Elevation Data, ECW, GRASS, TIFF/GeoTIFF, NetCDF,
  Imagine, and SDTS

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Extending Python with Wrappers

• Projections
• pyProjection (http//hobu.biz/index_html/software
  /pyprojection)
• For projecting coordinates from one to another
• Uses EPSG code system and/or you can roll your
  own
• SDE
• PySDE (hobu.stat.aistate.edu/pysde)
• Wrapper for SDE C API and has corresponding
  Python methods

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ArcObjects or Python?

• Rearrange the ArcGIS User Interface?
• Batch project a bunch of feature classes?
• Create new tool to edit special Widget feature
  classes?
• Create an Extension for ArcGIS?
• Automated Map Book Generation

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Thanks