Opening the hood: Extensions for Arcview

• Extensions are a critical part of the utility of Arcview

• They are specialized packages of tools that can be turned on or off depending on the need

• If you need to do it… its likely got an extension written by somebody that will do the job you need done!

The extension interface…

Under the file pull down there is an option for ‘extensions’… every one of these is an independent set of tools that open up a new set of possibilities….

Simply place a check mark in the box…

The default extensions….

• The imagine and CAD reader extensions are very useful and come as part of the default set of arcview extensions…

Extensions that must be purchased…

• ESRI has developed several extensions that are sold as ‘add-on’s’ to Arcview

• These extensions are almost as expensive as the base software package

• By far the most useful (and darn near indispensable) is the Spatial Analyst extension. The other extensions (image analyst, network analyst etc. are much more limited in their utility)

“hidden” extensions that come with Arcview

• Every installation of Arcview contains a ‘samples’ directory… note the path \esri\avgis30\arcview

Samples contd.

• Using a sample extension such as projector!

is fairly simple

The file *.avx (arcview extension) is copied to the ext32 directory

The new extension becomes visible in the extension option window and you are ready to go.

The desired extension is placed in the ext32 directory … and its ready to go

For the projector! Extension you get a new button which launches the dialog for the projector! tools.

Extensions from the world!

• The ESRI user community is very active and a tremendous number of scripts and extensions have been written….

• Again, if you need to do it… chances are somebody has written a script or extension to do the task.

»http://arcscripts.esri.com/

Loading a user extension…

• Simply download the desired extension• Unzip the file and move the *.avx file to the ext32

directory• Activate the extension and go….• Look at the top 10 download list… number one is

likely to be ‘x-tools’• This is an excellent extension written by guys at

the Oregon Department of Forestry… it is extremely useful…. Download it now and add it to your available extensions….

This file needs to go in the ext32 directory.

The xtools pull down is now available…

Try this extension….• Summary• Windingness works on the simple premise that the more curves a road

has, the more interesting it will be to drive or ride on.

It is designed primarily to help motorcyclists plan the route with the most corners.

Make a single polyline theme active in the TOC, then choose -> Theme -> Calculate Windingness. A new Windingness Index field (WIdx) will be added to the theme.

The lower the index, the longer the road is compared to its straight-line length - the script compares the length returned by Shape.ReturnLength to the distance between the first and last vertices.

Use the WIdx value in conjunction with a route-finding program to calculate the most interesting path through the landscape.

Told ‘ya there are virtually an endless number of extensions available….

Scripts….

• A little more complicated, but still manageable.

• Rather than create a button or pulldown menu the programmer will simply create a small program that you can run…

• The programming language is either ‘avenue’ (ESRI’s ‘almost’ visual basic language) or Visual Basic or C++.

The script GUI. Once your script is downloaded (usually *.ave or *.txt) simply copy-paste the text into a script window as seen here…

The compile button needs to be run first

Then the script can be run… using the little ‘running man’ button