Any thoughts on how to accurately apply GWR based on point/segment data. I am looking into the correlation btwn road accident severity (pointd) and lit/unlit segments of a motorway.

Most of the reading showed GWR applied on areas and not segments.

Initial considerations:

- dependent variable: centroid of each segment with total crash data weight by severity.

- explanatory variables: accidents data variables (lit/unlit, weather, lanes, speed, gender...)

Could use any help and advice!

Much appreciated.

Zak

Most of the reading showed GWR applied on areas and not segments.

Initial considerations:

- dependent variable: centroid of each segment with total crash data weight by severity.

- explanatory variables: accidents data variables (lit/unlit, weather, lanes, speed, gender...)

Could use any help and advice!

Much appreciated.

Zak

This is a great question! There is absolutely no reason that you can't use GWR to analyze road segments. As long as each of the centroids that you're analyzing have all of the necessary dependent and explanatory variables, you can use OLS and GWR to analyze them. With all of the tools in the Spatial Statistics toolbox, points, lines and polygons can be used as the unit of analysis. For lines and polygons, most of the time the centroid of the feature is being used for analysis (for instance if a fixed distance band is used to determine spatial relationships, that distance is from the centroid of a line or polygon, not the edge). The major exception is when polygon contiguity is used.

That being said, its important to remember that you always want to start out your regression analysis by finding a properly specified model using OLS. Once you find a properly specified model using OLS you can feel confident in the results that you find using GWR. What does it mean to be properly specified? Well, there are several assumptions of OLS that need to be met, and they are all explained in this ArcUser article called Finding a Meaningful Model. There is also a Regression Analysis Tutorial, and a free training seminar called Regression Analysis Basics. There are a bunch of other resources about the spatial statistics also available here: http://esriurl.com/spatialstats.

Hope this helps.

Lauren Rosenshein

Geoprocessing Product Engineer