On Mon, Feb 12, 2018 at 12:55 PM, Kevin Broderick <k...@kevinbroderick.com> wrote:
> Please, please, please don't convert rural roads to tracks based on > imagery alone unless it's incredibly clear (and that would exclude anything > with forest cover). > > While many of them should definitely be unclassified, not residential, > downgrading the main rural routes to tracks doesn't match local usage nor > the functional topology of the road network in such places. There are a lot > of USFS and BLM roads around here that are the only way to access > significant areas, that commonly see normal passenger-car traffic and that > can be traveled at reasonable speed in a sedan (or at 30+ MPH with a little > ground clearance and driving skill),. Having these differentiated from true > tracks (where even a stock 4x4 is likely going to be operating at 15 MPH or > less) is incredibly helpful for routing and visual use of the map, and it's > a lot easier to recognize what I'd call "areas of questionable data" when > they haven't been aggressively armchair-mapped. Also, the smoothness key is > really helpful for tracks and impossible to map from orthoimagery. > > Yes, yes, yes. In the rural areas that I can travel to readily, TIGER is downright hallucinatory (and there are few enough mappers that cleanup has been agonizingly slow). TIGER has roads in places where no road is, ever was, or even ever could be. (I've seen one going up a series of cliffs totalling about 2000 feet of ascent!) But even in 'leaves down' images, it's nearly impossible to see the forest roads, much less trace them, and there is definitely a wide variation in quality. Some of them are well-compacted sand and shale, that once they've been rolled in the spring, support driving at 30+ MPH. Others, I wouldn't bring my Subaru on. (Although I've been on a few of those in the ancient Ford Explorrer that the Subaru replaced.) Some are gated, some, you simply have to decide for yourself that they're not drivable. The 'dirt roads' range from 'highway=path abandoned:highway=track smoothness=impassable' to 'highway=tertiary surface=compacted smoothness=intermediate', with no way for an armchair mapper to tell among them. The old road maps that they used to give out at gas stations had, on many of these roads, "inquire locally for conditions," which is still good advice. The signage may say, "LIMITED PURPOSE SEASONAL-USE ROAD: No maintenance November 1-April 15" - but in practice, they'll keep it open later in the Autumn unless the snow comes early, and when they open it in the spring depends on when the crews can get it clear - it could be weeks late if there's been a bad washout or rock slide. There's absolutely no way to tag and encode that sort of thing. Inquire locally for conditions.
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