Q:

What are the most effective methods for monitoring changes in polygon layers over time

I work with many different thematic areas with GIS but there is one underlying task which as yet has never been satisfactorily methodized.  This is how to effectively monitor changes over time.  Particularly in the areas of Landuse planning and Environmental programs there is the need to analyse how layers have changed since the last update.  Non-GIS users want a simple understandable method to viusalise and document change but is often very complex in nature.  Usually my method involves geoprocessing tools such as "union"  or "identify" with ArcGIS to save old and new features in the same feature class and start the analysis from there.  This method is however sometimes difficult for non-GIS users to understand and then to query.  
What are the most effective methods for monitoring changes using GIS? 

A:

Aaron is right about raster- based analysis.  There are a lot of methods for change detection. One very popular method is the Post-classification Comparison.  I think the effectiveness of a method is related to the application you want (e.g vegetation change), so I am not sure if there is one method that is more efficient than the others.  Some of them (http://www.tandfonline.com/doi/abs/10.1080/0143116031000139863) are:

