[Talk-us-massachusetts] Hello, and some tagging questions!

[Aria Stewart]

On Mar 9, 2023, at 9:46 AM, Greg Troxel <gdt at lexort.com> wrote:

> Welcome to the list.

Thank you!

>> I’ve got questions about the best way to approach some situations:
> 
> There is a lot here, so a few generalities first:

[land use vs land cover]

Thank you for those concepts — that helps immensely as an overarching concept.

>> Parks: Salem has three notably different styles of map objects for parks. 
>> - Lappin Park
>> (https://www.openstreetmap.org/edit#map=20/42.52141/-70.89585) has an
>> outer park area, and inner grass and footpath objects.
> 
> Assuming that's a "city park", meaning human-controlled landscape for
> enjoyment (vs a nature reserve), which seems obvious given location and
> imagery, then leisure=park seems right.  That should be on the parcel
> boundary, more or less.  Having objects for paths makes sense.  footway
> implies a presumption for walking but allowing bicycles and horses.  So
> you may want to add access tags if those aren't allowed.

Excellent. I will do so as I clean some of this up! That’s actually the core of the work I want to do: record actual restrictions and access supports (benches etc) for civic action to improve accessibility of our town: people close to me have trouble walking long distances some times, and being able to show data for what’s an impediment to say, taking a walk to downtown, or to vote, or anything else is what I want to do.

> This park was imported from the MassGIS Open Space layer so probably
> needs cleaning up.  The boundary should be some blend of matching the
> parcel boundary (the actual boundary, and L3 parcels is a good guess
> absent better evidence), but perhaps extending to the demarcation
> between sidewalk and what feels like park.  I say this last point
> because the legal road layout and the in-use road layout are often a bit
> different (this is about how the world is, not OSM).
> 
> Modulo clenaing up the park object, this seems ok.

Excellent. I’ll try to refer to L3 data when I can.

> 
>> Lafayette Park
>> (https://www.openstreetmap.org/edit#map=20/42.51753/-70.89327) is
>> similar, though the ‘park’ area goes right up to the centerline of the
>> street. I’m never sure how precise to be vs how space filling.
> 
> Legally, the park goes to the edge of the parcel, and after that it is
> road.  Practically there is a transition from park grass to sidewalk or
> a fence.  The park boundary should be some blend of the two.  Definitely
> not road centerline as the road is not park.

Excellent. That aligns with my intuition, but I don’t want to come in like a ton of bricks on what’s already in many places an excellent map.

>> - Forest River Park
>> (https://www.openstreetmap.org/edit#map=17/42.50658/-70.88447) is a
>> mess of objects that don’t seem to quite line up with my GPS, and seem
>> too distinct — should the green spaces be separate from the park? Or
>> should the parking be on TOP of the park? how about the wetlands? It
>> all overlaps, it’s all part of the park (except maybe Pioneer Village,
>> which is at least fenced off separately, though it’s accessed through
>> the park)
> 
> A park can contain wetlands and paved areas for parking.  That is not
> logically inconsistent.  The leisure=park tag should be on a closed way
> matching the property boundary.   Then landuse for grass,
> amenity=parking, natural=wetland, etc.   If you draw a big grass polygon
> you may want to make it a relation and exclude the parking lot as a
> strategy, but the parking lot probably has road so probably you don't
> need to do that.
> 
> I don't know about Pionoeer Village.  You want to ask "does the
> government consider this to be 'in the park'" and look on L3 parcels to
> see if it is under a separate deed.  do park rules apply?  Am guessing
> it is separate.

That will be some research (though I’ve access to people who have good opinions on the legal and social differentiation, so it won’t be bad); the park is a hot mess on the map though, so cleaning it up is on my todo list. It’s possibly one of the most complex park parcels in the city, with its complex reef-beach-wetlands-special-use-playground-parking-car-chargers-ballfield-and-residence. It’ll be nice to clean that up but it’s tricky no matter how you slice it.

>> - Palmer cove park
>> (https://www.openstreetmap.org/edit#map=17/42.51452/-70.88898) has
>> some of the same amenities as Forest River Park, but they’re unmarked
>> — is that valuable to go trace out? How should they be layered and
>> tagged?
> 
> Yes, it's useful.   Just keep landuse on polygons aligned with ownership
> and new objects for landcover.

Excellent. Thank you!

>> The MassGIS aerial imagery and the Bing maps imagery are offset from
>> the buildings on the map in town pretty pervasively. What do you
>> trust? how do you deal with sidewalks that cross buildings? Is there a
>> strategy that doesn’t involve moving things?
> 
> I'll try to write more later, but generally I trust the 2021 MassGIS
> Aerials.  I do not trust or distrust Bing.  Buildings are from MassGIS
> from LIDAR and it's surprising they are far off.  I would expecte
> meter-level agreement.   Can you send an example?

https://www.openstreetmap.org/edit#map=19/42.51556/-70.88932 is a very typical example. This neighborhood is particularly dense, meter-level inaccuracies are likely to cause buildings and sidewalks to intersect, since buildings touch the sidewalks. Any misalignment will be noticeable in the blocks around here. Even the angle of aerial imagery is enough to obscure sidewalks with 2 and 3 story buildings here. Salem is dense! 

> (My basic advice is tread lightly for now in fixing this and don't do
> anythign large scale until we can discuss more.  THese are hard things
> to fix.)

Noted! That was my expectation. This is a tricky, old city, with tons of quirks and complexity and changes over time. 

Thank you for the expertise and care in your reply, this was very helpful and lets me at least make modest impovements to the status quo.

Aria


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