[Talk-us-massachusetts] A different method to correct Open Space Polygons in MA

[Alan & Ruth Bragg]

I spend a lot of time re-aligning open space polygons to the MASSGIS L3
imagery.

I've been studying Oliver and today I did an experiment using Monroe State
Forest in Monroe MA.

I downloaded from Oliver
<http://www.mass.gov/anf/research-and-tech/it-serv-and-support/application-serv/office-of-geographic-information-massgis/datalayers/download-level3-parcels.html>
the zipped Monroe M190 L3 Shape file <about:invalid#zClosurez>.

Unzipped the file into 20 files <about:invalid#zClosurez>

I downloaded the Monroe MA area and added the MASSGIS L3 imagery in JOSM

I then opened the M190TaxPar.shp file in JOSM and compared it with the
MASSGIS L3 imagery

The polygon was a perfect match for the Forest in the MASSGIS L3 imagery
layer. The OSM polygon was mis-aligned.

Used Edit-Copy(Ctrl+C) to copy the selected polygon from the M190TaxPar.shp
layer

Switched to the JOSM "Data" layer

Used "Edit-Paste at source position" (Ctrl+Alt+V) to add the polygon to the
Data layer

I selected both the new polygon and the old polygon and used "Replace
Geometry" Ctrl-Shift-G which deleted the old polygon but retained the
attributes and the history.

I then deleted attributes that had been carried forward from the shp file.
They were:
"LAST_EDIT=20111019
LOC_ID=M_78335_941081
MAP_NO=401
MAP_PAR_ID=190/401.0-0000-0037.0
NO_MATCH=N
POLY_TYPE=FEE
SHAPE_Area=8207306.72903
SHAPE_Leng=17549.8266705
SOURCE=ASSESS
TOWN_ID=190"

I'd really appreciate any comments, suggestions or warnings regarding this
process.

This method seems to have worked. The polygon had 233 nodes and would have
been much more work to re-align manually.

One caution: you have to be very careful which layer is active (the check
mark). If the shp file layer is active and you select upload, you'll be
faced with doing your first "revert". This has not yet happened to me.

Note, the process was a little more complicated than described above
because the polygon was part of a relationship and took a few more steps.

​Alan Bragg
781-275-1737
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