I've rendered an area locally at
http://maps.paulnorman.ca/surreywater.html?bbox=-122.88,49.08,-122.82,49.12
This is OSM data + drains + streams. Culverts are not included. There is
some overlap between NHN and Surrey data which would not be present in the
import.
An example of the worst case for waterways is can be found in Bridgeview at
http://maps.paulnorman.ca/surreywater.html?bbox=-122.8773,49.2068,-122.8680,
49.2108
Hopefully this will help with determining if we want the roadside ditch
information.
From: Paul Norman [mailto:penor...@mac.com]
Subject: Re: [Talk-ca] [Imports] Proposed import: Surrey, BC waterways
From: Richard Weait [mailto:rich...@weait.com]
On Tue, Mar 29, 2011 at 2:31 AM, Paul Norman penor...@mac.com wrote:
In short, the waterways in Surrey BC are largely from NHN data which
in some cases is accurate, but tends to be 20-30 years old. I'm
proposing importing data from the city, licensed under PDDL. I'm at
least 2-3 weeks away from being ready to do the import as I have
some other priorities currently but I wanted to get feedback.
I see this import as fixing two problems. The first is the old NHN
data. The second is the high number of unmapped ditches in Surrey.
Because of the nature of the soil, it is very common for houses to
have drainage ditches in front of them. These are largely unmapped,
but the shapefiles appear to have all ditches.
Legal: The data is licensed under PDDL, a compatible license.
Accuracy: The positioning is very good.
Completeness: Not all culverts are mapped. Random checks revealed no
missing ditches or streams.
Existing data: It was all mapped by me or imported. I am proposing
removing it.
There are more details at
http://wiki.openstreetmap.org/wiki/Canada:British_Columbia:Vancouver
/I mports /Surrey/Waterways about the exact tagging. I intend to
refine this, but this may require a couple of site surveys. Before
importing I will post a sample .osm file for review.
I think that the Surrey, BC data under PDDL is wonderful. And I know
that you have previously looked at their address data and road data
and found it very helpful with addr:, maxspeed and hgv information.
This data is more controversial, which is why I'm asking for feedback
early in the process.
I wonder if these common roadside ditches will share the same
drawbacks as sidewalks in some other areas. In fact, if sidewalks
exist in this area as well, the ditches may compound the problems of
sidewalks. In summary portions of the OSM community are divided about
sidewalks. Some feel that mapping sidewalks isn't needed where they
are common. If all roads have sidewalks, why map them separately?
Others feel that sidewalks should be indicated as tags on roads, like
sidewalk=both for both sides. Others feel that mapping each sidewalk
with a separate highway=footway way adds important detail to the map
for pedestrians. Still others find that editing an area with a
substantial number of separate sidewalk ways makes editing more
difficult; smaller download areas are permitted, editing the shape of
a road means editing the shape of two sidewalks as well, adding other
objects like building and POI have additional ways to snap to
unintentionally.
Good points. If we decide against importing the ditch data, I can rework
the files to only include streams and named ditches.
I think the ditches are worth mapping. The ditches in question are
typically 2-5m wide and can be seen on imagery.
They have culverts to allow foot and vehicle traffic to pass over them.
I view them in many ways as analogous to fences on private property
which are often mapped. Like fences, they are physical features which
are significant if crossing, but placed in a way that doesn't impact
most foot traffic.
The shapefiles can be broken down into 4 relevant groups of ways.
The first of these is streams. These typically meander, are in forested
areas, are natural as opposed to constructed, and often have names. In
my view, these are definitely worth importing.
The second of these is ditches in rural and agricultural areas. These
are relatively long with unbroken stretches. They sometimes have breaks
where they go into culverts to go under roads or footways. These are
also worth importing, but hard to distinguish from the third category.
The third is ditches in suburban areas. These are used for drainage.
They are 2-5m wide, and frequently broken by culverts. They go around
blocks often and don't cross under roads. They eventually drain into the
storm drain system. This is what the debate should be about. I feel
they're worth mapping as they are significant physical features.
The ditches are not found everywhere, I found them mainly in areas
constructed in what was damp soil in the 1970-1990s.
The fourth is culverts. They come from a separate shapefile and join the
