Route breaks, fill -- eg Fernandina to St Augustine

[gregallensworth]

In the routing demo, the route from Fernandina to St Augustine.

• Follow the route south from San Fernandina.
• When you get to Amelia Island State Park, see that there is a break of about 1000 feet.
• These steps are skipped because 659474 Timucuan Trail is close enough that it "snaps" and a solution was found.

Reducing the snap tolerance from 0.004 to 0.002 reduces this effect by seeking closer snaps, but doesn't eliminate them completely.

Sorting the candidates by nearness of endpoint, could reduce this by causing it to look harder for snaps, but would be at odds with sorting the candidate paths by their "likely nearness" to the target and thus being more efficient in guessing routes.

In this specific case the added directions would have filled in the gap, with directions that a human would not have found useful: "parking lot" and "underpass" were the omitted segments. In this specific case, their omission was likely good... but I won't presume that that's always good.

[gregallensworth]

Same route, second condition:

• Continue following south, where it crosses the St Johns River.
• Note the skipped segments "St Johns River Ferry Access"

Same as above, maybe the omission here is a good thing for readability, though the gaps in the line are unpleasant.

Continue further south, to the connection at Hayport Road:

• A1A to Hayport, has a visible break, not due to bad segment joining, but because there really is a break in the coverage.
• Same where Hayport turns off onto Plaza St.

Best solution here may be a cleanup which "connects" the two lines, by adding a new nameless segment or else by end-aligning the lines and faking their vertices to add a connection.

[gregallensworth]

One of the Hayport breaks. Question here is, whether we should have the router connect these ends to smooth things out.... given that that can cover up topology errors which folks may want to repair?

[gregallensworth]

Same Fernandina to St Augustine route, at St Johns River. The right-side one, connecting the ends to make a continuous line, would show a deviation from the path. (worse than that already caused by the ST_SIMPLIFY to clean up some flourish-crumbs).

[gregallensworth]

Got approval to go ahead and connect these.

• The topology fixes will eventually make for fewer of them, in straight-line conditions.
• In cases such as the curve above, we'll accept it and GIS will fix them as needed by merging them.

[gregallensworth]

All set. If the gap between two segments is more than 0.0001 degrees, then the first point of the next segment is appended to the prior segment. Thus, the lines will always overlap and the effect is much smoother.