[Talk-us-massachusetts] Hello

Thu Dec 17 14:14:17 UTC 2020

Tom Parent <tomparent at gmail.com> writes:

> I'm a new but active mapper out of Belmont.  TomPar on OSM.  I've chatted
> with some folks on the OSM Slack site but didn't think to subscribe to
> this.  Seems there are different people on this list?

Welcome to the list.  Yes, each OSM communications mechanism has
different pepple, with overlap of course.  Personally, I don't think
open data/open source projects should use proprietary tools, so I do not
deal with Slack.

(I used to live in Belmont pre-OSM, and used to be there a lot, but not
so much recently.  You'll probably see my userid (gdt) in changesets.  I
map around Stow mostly now, and have done most of the trail mapping in
our conservation lands.)

> my mapping passion is making public accessible parcels available for
> outdoor activities more clear and dataset/visually consistent across New
> England...mostly eastern MA and VT that I'm most familiar with after
> decades of traipsing the countryside.

A caution when you mention visually consistent.  There are fairly few
points of doctrine in OSM, but a big one is having the database
represent reality using tags that are defined by consensus, and not
adjusting tags to achieve a particular rendering.  Various renderers
make choices about what to show based on what the renderer maintainers
think is important.

Specfically, my town has a lot of land that is "conservation land",
which means maintained in a natural state with trails for walking/etc.
This is tagged "landuse=conservation" and "leisure=nature_reserve"
following longstanding practices.  It also now has
"boundary=protected_area" which is a modern Euro convention foisted on
the rest of OSM.  While tags are just tokens, the use of that as
boundary leads to confused thinking that the polygon feature around the
edge is the important thing, and this bleeds into the default render.
In reality, all those tags describe a property of the area, not the
edge.

The maintainers of the standard style, that appears on
openstreetmap.org, appear not to think that open space mapping is
particularly important.  Things like golf courses render more
prominently than conservation land, for example.

However, the great thing about OSM is that anyone can create a render
how they want, and show what matters.  Besides the other styles on the
main map, there are other map displays on the web.  Also OsmAnd does its
own rendering, and you can tweak it - but it respects
landuse=conservation.

[I'm reordering your text to reply.]

> I'd like to help contribute to tagging/mapping convention standardization.
> I'm particularly interested in burgeoning efforts like:
> https://wiki.openstreetmap.org/wiki/United_States/Public_lands

We have documented the local consensus (as reached here) on conservation
mapping:

  https://wiki.openstreetmap.org/wiki/Massachusetts/Conservation

On a quick skim of the Public_lands page, things seem mostly
consistent.  A few points:

  The big difference is that we do not recognize the deprecation of
  landuse=conservation, and ask that all parcels for which "preserving
  the land in a natural state indefinitely", more or less, is the
  primary purpose, have a landuse=conservation tag.  However this is not
  in conflict as the other pages do not specify a landuse.

  To understand the public_lands page you need to take a 16-hour course
  in IUCN rules.  That's a joke, but the whole scheme of numeric code
  points is contrary to larger OSM norms of tags that while technically
  tokens with defined meaning are somewhat understandable.  I'm a long
  term mapper (since 2009) with a degree in computer science -- and I
  find it way too confusing.

  There is a real focus on government with protected_area (not
  surprising as it seems to be a UN thing).  But in MA, there are a
  tremendous number of places that are legally protected from
  development by Conservation Restrictions, which are easements recorded
  at the registry of deeds, some held by towns, and some held by land
  trusts.  We consider those entire sufficient for protected_area
  status, but don't use that tag for general municipal land without a CR
  or legal conservation status even if it is currently used as a
  nature_reserve.

Also landuse=forest means the principal use is forestry as opposed to
principally conservation with some forestry that is not inconsistent
with long-term open space conservation.  Some people use landuse=forest
to show that there are trees, or because the parcel is called e.g. "Stow
Town Forest"; I think both of these usages are incorrect.

> I hope I've already made some positive contributions to parcels in
> Belmont/Arlington/Lincoln.  I haven't received any negative changeset
> comments yet so presume everything is OK.  I did take some time to learn
> the culture of OSM, get up to speed with JOSM, before really digging in.
> Thanks to whoever made available the MassGIS orthos and parcel layers in
> JOSM.  It's been extremely useful.

You're welcome - that was a group effort over time by several of us on
this list.  There is also an easement layer from MassGIS but they don't
have a tile service.  That is only occasionally useful; e.g. one
conservation parcel in Stow does not have any frontage and there is an
access easement that in included in the leisure=nature_reserve polygon.

I haven't really been paying attention recently to Belmont.  The only
thing I would throw out from a quick glance at the standard render is
that there is a surprising amount of solid green.  If you have tagged
things according to the guidelines and that's how it is, great --
perhaps the standard render render is changing.  But if you are choosing
tags to make things green, that's more or less not ok.  I believe a fair
bit of Belmont conservation land should be leisure=recreation_ground
rather than park, but I don't tnink I'm seeing park green.

And, if you have figured out IUCN tagging, and put in code points that
are right, and that makes conservation green, then thank you and please
explain the key points!

Another big issue is the difference between land use and land cover.  In
geography these are distinct concepts, and in OSM they mostly are but
the default render tries to do both.  That's hard, and it does a decent
job at an impossible task.  Plus, OSM is confused in that landuse is
denoted sometimes by landuse= and sometimes by other tags.  Similarly
for landcover; it's not landcover=foo, but some mix of various things
which are all essentially landcover.  So semantically it's a bit of a
mess.

There's another difficult issue, which is natural=wood sorts of tags
(landcover) and areal extent.  This denotes that an area is tree
covered.  Around me (compared to Belmont which is the city :-) trees do
not stop at conservation land boundaries, and looking at imagery you
cannot figure out where conservation land stops.  So putting landcover
tags on parcels is in my view basically wrong, unless the landcover
really is limited to the parcel and uniform within it.  I basically
don't believe that will ever be the case.  But I can believe in Belmont
that this will be far more true than it is in Stow, given the local
culture and zoning in terms of adjacent land use, where non-conservation
land is split into 1/8 acre parcels, completely cleared, and having
houses, driveway, lawn and pools only with a few trees.

If you have micromapped grass vs trees from imagery, and gone over the
parcel line when the landcover crosses, so that your landcover tagging
is disconnected from ownership, then I salute you for amazing work.  And
if so, I'd encourage you to do that micromapping of the whole town
regardless of ownership.  That's the great thing about OSM, how each
person can take really good care of a few areas and together we have an
amazing map.

Also, if you haven't put in stone walls those are great to add
(barrier=wall wall=dry_stone).

I'll try to take a look in more detail and I'm sure a few others will
too.

MassGIS publishes an open space layer and you can see it on Oliver.  The
quality of the geometry is variable but it's great to use as a clue what
to go look at.  An earlier version was imported long ago (2008?).

  http://maps.massgis.state.ma.us/map_ol/oliver.php

Finally, I want to point out a site run by Jason Remillard, one of the
members of this list, that does a conservation-focused render and
analysis.

  https://www.mass-trails.org/
  https://www.mass-trails.org/towns/Belmont.html

You may find this useful not only to look at, but to find things that
maybe you should tag more or differently.

Long ago we had a few geo meetups in Cambridge (at CBC), and it would be
good to do that again, when we reach Phase 4.

Greg
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