Full metadata for the National Elevation Dataset (NED)
was not available at the time the data were downloaded
from the US National Map web site (seamless.usgs.gov).
However, four tiles were donloaded from this site, and
processed as followed:

-  Each of 4 data tiles were projected to NH State Plane
-  PBNH buffered by 1 mile to PBNHBUF
-  Each of 4 tiles was clipped to PBNHBUF to
   create neg (northeast grid), nwg, seg, swg
-  Each was then resampled:  segr = resample(seg,87.7,bilinear)
-  Four resampled grids merged into nedbuf.
-  Nedbuf multipled by 3.280833 to convert z units to
    ft - created nedbuf_zft.