On Sun, Jun 6, 2010 at 11:04 PM, John F. Eldredge <[email protected]> wrote: > From my personal experience in the USA, skipped house numbers are most > likely to occur on the inside of a curve in a road. Since there is less > space available on the inside of the curve, and since road-planners > generally want to have the house numbers on both sides of straight > stretches be in sync, they will skip some numbers on the inside of the > curve. A street with a tight (small-radius) curve will have more > skipped numbers than a street with a very gentle, large-radius curve.
In many places, not only are two sides of a street kept in sync, but all parallel streets are supposed to be in sync as well. Therefore an address grid is established, with a fixed ratio relating housenumbers to distance. In urban areas with regular grids of numbered streets, this is often 100 housenumbers to a block, which typically means 1200 per mile. In areas dominated by the mile-grid, housenumbers are calculated from 1000 per mile (often called the "5.28 feet" system). In some places where the roads are less regular, the ratio could be set so that addresses approach but do not exceed some arbitrary number (such as 9999) at the edges of the coverage area. That last tactic is why in Franklin County the ratio is about 700 per mile. Anyway, with addresses relating more to distance than sequence, skipped numbers are the norm. > If the Karlsrue schema doesn't do this, how does it handle curves? Are > the lots on the outside of curves always significantly larger than those > on the inside of the curves? The Karlshrue schema specifies a few different (related) techniques to tag addresses. The most micro-mapped method is to have a node for each address, which eliminates all concerns about curves, skipped numbers, and synchronization, though it requires the most local knowledge. Address interpolation can be used, which (if one way represents both sides of the street) will basically assume the two sides are synchronized. It doesn't specifically indicate anything about the sizes of lots or whether any numbers are skipped, or which side of the street any given address is on. The middle ground here, and the direct answer to the above question, is to have an address-interpolation way along either side of the street, each specifying whether the addresses along it are odd or even. This way, the tagging can show that the two sides of the street get out of sync if this is the reality on the ground. There's still no simple way to tag whether a number here or there is skipped, but that's not really a problem for most people. If you really want to have the data show that certain housenumbers exist and certain housenumbers don't, then just don't use address interpolation. Karlshrue works fine with just addresses on individual nodes. -- David "Smith" a.k.a. Vid the Kid a.k.a. Bír'd'in Does this font make me look fat? _______________________________________________ newbies mailing list [email protected] http://lists.openstreetmap.org/listinfo/newbies
