R help - Oct 2008 - Using an image background with graphics

I would like to use a map or aerial photo as a background to plotting
solid lines and text, and semi-transparent color contours, in base and
lattice graphics.  Plot coordinates need to be consistent with the
georeferenced background.  For example, a color contour plot would have
an gray-toned aerial photograph as a background for overprinted
semi-transparent color contours of some spatially dependent variable.
Can anyone point me in the right direction on how to do this?

Thanks,
Scott Waichler
Pacific Northwest National Laboratory
scott.waichler at pnl.gov

On Monday 13 October 2008, Waichler, Scott R wrote:
> I would like to use a map or aerial photo as a background to plotting
> solid lines and text, and semi-transparent color contours, in base and
> lattice graphics.  Plot coordinates need to be consistent with the
> georeferenced background.  For example, a color contour plot would have
> an gray-toned aerial photograph as a background for overprinted
> semi-transparent color contours of some spatially dependent variable.
> Can anyone point me in the right direction on how to do this?
>
> Thanks,
> Scott Waichler
> Pacific Northwest National Laboratory
> scott.waichler at pnl.gov
>
See spplot() and associated examples of how to use 'sp' class objects.

Here is one worked exampled with sp objects:
http://casoilresource.lawr.ucdavis.edu/drupal/node/442



-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341

The rimage package has functions for reading in and plotting jpeg files that you
could use for displaying the photograph.  If you then can find 2 points in the
image (not on the same horizontal or vertical line) for which you know the
coordinates in the coordinate system that you want to plot in, then you can use
the updateusr function from the TeachingDemos package to set the user
coordinates, then use points/lines or other functions that can add to the
current plot (e.g. contour with add=TRUE) to overlay the information of interest
to the plot.

Also look at the squishplot function in TeachingDemos for one way to set the
aspect ratio of the original image.

Hope this helps,

________________________________________
From: r-help-bounces at r-project.org [r-help-bounces at r-project.org] On
Behalf Of Waichler, Scott R [Scott.Waichler at pnl.gov]
Sent: Monday, October 13, 2008 3:02 PM
To: r-help at stat.math.ethz.ch
Subject: [R] Using an image background with graphics

I would like to use a map or aerial photo as a background to plotting
solid lines and text, and semi-transparent color contours, in base and
lattice graphics.  Plot coordinates need to be consistent with the
georeferenced background.  For example, a color contour plot would have
an gray-toned aerial photograph as a background for overprinted
semi-transparent color contours of some spatially dependent variable.
Can anyone point me in the right direction on how to do this?

Thanks,
Scott Waichler
Pacific Northwest National Laboratory
scott.waichler at pnl.gov

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