Binary and Ordinal Data for Kirging or other Interpolation techniques?

[LokKwan]

Hi all,

I have a question regarding interpolation technique and I hope someone here can give me some help. I???ve done the Geostatistic ESRI online tutorial, which I am pretty sure many people in this forum have also completed. The tutorial used all sort of interpolation tools to predict Ozone level across California based on continuous data collected from air quality stations.

I would like to do the same thing but I am wondering if I can do this for ordinal or binary data. For example, I have some public transit satisfaction level data from a public transit customer satisfaction survey. In this case I am almost certain that you can use Kirging to predict the satisfaction level across the study area base on sample data. However, I am wondering if we can do interpolation on binary data. For example, when the survey ask if you have ever used public transit there will be a Yes or No answer. Similar to binary regression, I am thinking if I can assign a dummy variable (Yes = 1, No = 0) as the input in the ArcGIS interpolation tool to predict the location of the public transit users and the non-public transit users across the study area.

Thanks,
Jason

[EricKrause]

Indicator kriging and Probability kriging are both designed to work with binary data.  Choose kriging and supply your binary dataset on the first page of the Geostatistical Wizard.  On the second page, choose Indicator or Probability from the kriging types, then proceed as usual.  The prediction surface will represent the probability that the binary variable is a 1.

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00310000004n000000.htm
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Understanding_probability_kriging/0031...

[LokKwan]

Thanks for the help! Do you know of any ESRI or open source online tutorial that might prepare me to conduct interpolation map with Binary or Cateogorical data?
Your help is greatly appreicated.


Jason

[EricKrause]

If you've done the Geostatistical Analyst tutorial, you shouldn't have any problems performing Indicator or Probability kriging.  The process is the same.  As for kriging on ordinal data, I know there has been research done in this area, but I'm not up-to-date, and we don't have that capability in Geostatistical Analyst.

[EricKrause]

Aye, this is embarrassing.  It's been so long since I used Indicator/Probability kriging that I forgot exactly how they work.

For binary data, it doesn't make sense to do Probability kriging, and there's a bit more to Indicator kriging than I remembered.  Set the Threshold value to 0.5, then after creating your surface, areas with a predicted value below 0.5 should be classified as a "0" and any value above 0.5 should be classified as a "1".  You can do this by symbolizing the geostatistical layer, or you can convert it to raster and use the Con tool in Spatial Analyst.