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<div class="moz-cite-prefix">On 12/30/2019 7:27 PM, Greg Troxel
wrote:<br>
</div>
<blockquote type="cite" cite="mid:rmieewluyoq.fsf@s1.lexort.com">
<pre class="moz-quote-pre" wrap="">Interestingly I see a small consistent shift between the new layer and
OSM, in that map.
I am not clear how the property map is dealing with the two datums.
(None of this datum stuff is easy....)</pre>
</blockquote>
<p>I first noticed this shift about a year ago when the iD editor
software switched to using a different TMS server for the L3
parcel map. I later saw this email talked about the change of tile
servers: <a
href="https://lists.openstreetmap.org/pipermail/talk-us-massachusetts/2018-November/000424.html">https://lists.openstreetmap.org/pipermail/talk-us-massachusetts/2018-November/000424.html</a>
<br>
</p>
<p>At the time I was not subscribed to this list so I posted about
it here:</p>
<p><a href="https://forum.openstreetmap.org/viewtopic.php?id=64699">https://forum.openstreetmap.org/viewtopic.php?id=64699</a></p>
<p>Not sure if my conclusions there were correct however. <br>
</p>
<p>I had assumed that the downloadable files from MassGIS stayed
fixed at the original datum, while the TMS applied some sort of
techtonic plate movement based correction. The yearly divergence
rate noted in my forum post is not big enough to account for the
difference we see today, and may be partly due to the initial
error in the original datum. Probably only MassGIS would know the
source(s) of the difference.</p>
<blockquote type="cite" cite="mid:rmieewluyoq.fsf@s1.lexort.com">
<pre class="moz-quote-pre" wrap="">
(I see what you mean about Braintree.)</pre>
</blockquote>
<p>Looks like mainly north half of Braintree is a mess. These
imports were done by crschmidt in January 2009.<br>
</p>
<p>These are some of the changesets I found on bad Braintree
buildings but It looks like the changesets cover huge areas:</p>
<p><a href="https://www.openstreetmap.org/changeset/727079">https://www.openstreetmap.org/changeset/727079</a></p>
<p><a href="https://www.openstreetmap.org/changeset/727079">https://www.openstreetmap.org/changeset/743822</a></p>
<p><a href="https://www.openstreetmap.org/changeset/727079">https://www.openstreetmap.org/changeset/743003</a></p>
<p>The later imports done in 2013 look good.</p>
<p>-Wayne<br>
</p>
<blockquote type="cite" cite="mid:rmieewluyoq.fsf@s1.lexort.com"> </blockquote>
<blockquote type="cite" cite="mid:rmieewluyoq.fsf@s1.lexort.com">
<pre class="moz-quote-pre" wrap="">
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</pre>
</blockquote>
<p><br>
</p>
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