Topographic Position Index (TPI)

Notice: For ArcGIS users, portions of this tool have been rewritten and are available in the ArcGIS Land Facet Corridor Designer extension.

NAME: Topographic Position Index (TPI) v. 1.3a (Click name to download)

View Online PDF Manual:

View and Download TPI Poster

View Original TPI Poster by Andrew Weiss

Aka: tpi_jen.avx

Last modified: September 15, 2006

TOPICS: Topography Position Index TPI Landform Slope Classification Standardization Neighborhood Statistics

AUTHOR:
Jeff Jenness, GIS Analyst

Jenness Enterprises
3020 N. Schevene Blvd.
Phone: 1-928-607-4638
Flagstaff, AZ 86004 USA
Email: jeffj@jennessent.com
Web Site: http://www.jennessent.com

DESCRIPTION: This extension calculates Topographic Position Index (TPI) grids from elevation grids, and provides a simple and repeatable method to classify the landscape into slope position and landform category using the TPI values.

This extension provides additional functions to standardize and classify grids, and to generate grid and neighborhood statistics.

Acknowledgments: The author gratefully acknowledges the work of Andrew Weiss who originally developed the TPI methodology and concepts. This extension automates Weiss’ methods and allows users to save and share classification criteria sets.

The author also acknowledges and thanks Joyce Miller of the National Oceanic and Atmospheric Administration for suggesting this tool and for funding an early version of it.

REQUIRES: Spatial Analyst

This extension also requires that the file "avdlog.dll" be present in the ArcView/BIN32 directory (or $AVBIN/avdlog.dll) and that the Dialog Designer extension be located in your ArcView/ext32 directory, which they usually are if you're running AV 3.1 or better. The Dialog Designer doesn't have to be loaded; it just has to be available. If you are running AV 3.0a, you can download the appropriate files for free from ESRI at:

http://support.esri.com/index.cfm?fa=downloads.patchesServicePacks.viewPatch&PID=25&MetaID=483

REVISIONS:

Version 1.01 (July 12, 2005) corrects a bug producing an error message stating that “The script ‘grid-tools_jen.RescaleRainbowIncrements” could not be found.

Version 1.01a (July 17, 2005) makes minor changes to the extension and edits to the manual.

Version 1.2 (March 22, 2006) fixes an intermittent bug related to creating, saving and reusing custom landform classification sets, and which displayed an error stating that “Variable theTPI1Units2GridString has not been initialized.”

Version 1.3 (April 24, 2006) fixes 3 bugs:

1) A bug triggering an error message stating that:

	Error in ''
	Error Message: A(n) Grid object does not recognize request <=-
	Error Position: [some number]

2) A bug that might occur if a criteria set was used that excluded all the cells.

3) A bug that might cause ArcView to crash if the extension was used in the Chinese version of ArcView.

Version 1.3a (September 15, 2006) fixes a bug in which Slope Position and Landform class grids were not sorted correctly, so that classes that referenced the same region on the landscape might not receive precedence according to class number.

Recommended Citation Format: For those who wish to cite this extension, the author recommends something similar to:

Jenness, J. 2006. Topographic Position Index (tpi_jen.avx) extension for ArcView 3.x, v. 1.3a. Jenness Enterprises. Available at: http://www.jennessent.com/arcview/tpi.htm.

Please let me know if you cite this extension in a publication (jeffj@jennessent.com). I will update the citation list to include any publications that I am told about.

General Instructions:

Begin by placing the tpi_jen.avx file into the ArcView extensions directory (../../Av_gis30/Arcview/ext32/).
After starting ArcView, load the extension by clicking on File --> Extensions… , scrolling down through the list of available extensions, and then clicking on the checkbox next to the extension called Topographic Position Index
This extension will new menu to your View:

For detailed instructions, view on-line PDF version of TPI Documentation

Enjoy! Please contact the author if you have problems or find bugs.

Jeff Jenness jeffj@jennessent.com

Jenness Enterprises http://www.jennessent.com

3020 N. Schevene Blvd. (928) 607-4638

Flagstaff, AZ 86004

USA

Please visit Jenness Enterprises ArcView Extensions site for more ArcView Extensions and other software by the author. We also offer customized ArcView-based GIS consultation services to help you meet your specific data analysis and application development needs.