[Talk-us-massachusetts] MassGIS L3 parcels and datum

[Greg Troxel]

(I realize this query is deep in the weeds.)

Recently Joe and I have been discussiing the representation of
conservation land boundaries in OSM, for abutting properties that are in
Acton and Stow.  There is a lot of complexity in such a situation, in
that the actual stone wall on the ground, the actual town line, the town
line data in OSM, and the L3 parcels data may all be different.  I'm
writing to ask a far narrower question -- but thought the background
would help motivate it.

MassGIS has published the L3 parcels layer.  They use the NAD83 datum,
and OSM uses "WGS84"*.  I am wondering if the web service that we use
for L3 is really in WGS84, or if it is in NAD83.  And if NAD83, if there
are approaches for dealing with transforming it to WGS84 in josm and
other editors.


* There is a further nuance that WGS84 is a family of datums and that
  early versions are, more or less, not very accurate.  I am assuming
  that OSM data should be in the most recent realization, WGS84(G1762).
  I am also ignoring the motion of ground points with respeect to
  WGS84(G1762).