> Now the problem is mapping. Luckily, I have a good sense of
> orientation in the field plus photographic memory, being able to return
> directly to CP sites visited years before. But it is simply impossible to
> explain to anyone how to arrive at many of these sites! I try and include
> as much location data as possible along with the herbaria I collect, but
> that is unfortunately often far from precise.
For your extensive and ongoing field work, I think you should seriously
consider getting a hand-held GPS receiver.
These have now gotten down below $300 USD in price and will give you a
Lat/Long fix within about 100 meters. This allows precise renavigation
to the site, and provides data that can be precisely overlayed on topo
maps or satellite images. In most industrialized countries, differential
GPS is available with resolution to 1m or so.
The last integrated circuit technical conference I attended had a paper
describing a chip for a *wrist-watch* GPS receiver!
Satellite data exists for multiple visible and non-visible wavelengths,
radar height mapping, geomagnetic variation, water content, etc. It can
be post-processed to indicate blacktop, gravel, compacted soil from
ancient roman or mayan roads, of C3/C4 chlorophyl ratios, etc. Maps
have be generated based on IR profiles of specific species (eg: cannabis
sativa) The scientific relevance of this data is only just now being
understood. Every year, new higher resolution surveys are being
declassified from US military systems.
While notations such as "3.7 km on west fork road off IS373, down wadi
250 meters to northeast, plants on south-facing slope" are handy in the
field, they are essentially useless for a scientific plant census of
global scope.
-- Rick