[R] Superimposing vector polygons over raster grid in a plot

[Rick Reeves]

Hello:

I would like to superimpose vector polygons (state outlines) from a 
Shape file on top of a satellite image,
imported into a SpatialGridDataFrame from GEOTIFF via gdal_translate and 
readGDAL.

When I plot polygon and point shape files in R, into 
SpatialPointDataFrame and SpatialPolygonDataFrame,
the two feature sets line up geographically, so it seems logical that a 
SpatialGridDataFrame should behave
in the same way.

 From my initial research, the spplot function is the correct function 
for plotting grids/images with axes and
annotation.

The big question is, how do I incorporate a Spatial(Points or 
Polygons)DataFrame into the spplot display list?

It seems as though many scientists would like to create such plots 
without resorting to GRASS or
another GIS.

Thanks for any advice,
Rick Reeves

Rick Reeves	
Scientific Programmer / Analyst	
National Center for Ecological Analysis and Synthesis
UC Santa Barbara
reeves at nceas.ucsb.edu
www.nceas.ucsb.edu
805 892 2533