snip
> Would anyone know : 1) whether true North or magnetic North would
> have been used in the patent description, and 2) how many degrees of
> declination between true north and magnetic north was observed in the
> tidewater in 1701?
There is a major difference in The North and Mag NOrth.  The surveyors would
have used a declination angle to set there north on the transit.  A
professional Land Surveyor or Engineering firm in the area should be able to
give the Dec. Angle.


>
> I have also been trying to map the parcel using Geographic
> Information System (GIS) software (ArcView) over an orthophoto of the
> area in question. That leads to a related question. Are GIS systems
> now being used in professional historical research? They seem to me
> to be potentially very valuable in storing, presenting and sharing
> spatial data.
Trying to marry an Ortho photo and GIS is tricky.  The only part of an ortho
photo that is not distorted in the middle third.  So if you are laying it
out on top of the ortho photo with the correction factor loaded in you will
get skewed legs.  and the lack of the Dec. Angle will skew your legs.

Deborah Byrd

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