Premise

 
Premise
Wanted a simpler way to access the USGS seamless elevation look-up service. Python seemed like a logical start. Note that the response from the USGS webservice is not correctly identified as valid XML by the python XML-parser. Therefore there is a small amount of scrubbing used to coerce the response into valid XML. Comments on why this is, or is not, a good idea are welcome.

 
Update It looks like the USGS service does not accept POST-style requests. I have made some small changes to the script below.

 
Premise:

Setting the magnetic declination on a compass is a critical step in accurate measurement of bearings that can be translated to map or survey. As the location of the magnetic north pole is constantly moving, the magnetic declination reported on older topographic maps or compass housings are probably out of date. Current declination values for a single point, or for large regions can be found on the NOAA sites:

• single point
• global maps

These resources are helpful, but a current, detailed (state-level) map of magnetic declination would be interesting.

 
Premise:
A generic press-quality plotting system for GRASS, based on GMT. Still a ways to go.

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Two visualizations of the deviance between coordinates positions, at the control point locations.

 
... Continuing from the initial example session in R ...

 
First the output from R:
Looking at the residuals from the regression model used to map bad coordinates (x,y) to good coordinates (nx,ny):