Thread: geocoding, book referrals. was: [Gpsbabel-misc] OT, Data vs Maps
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From: Robert L. <rob...@us...> - 2005-12-05 18:00:20
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I'm reluctant to play along with an OT discussion, but I'll turn this back into a plug for our own (and related literature) in a moment... > >> http://geocoder.us/ << > >> http://developer.yahoo.net/maps/rest/V1/geocode.html << > > Thanks! > > Both look like great resources... although the us census data from > geocoder got the city wrong on my address ;-) Geocoding is hard. The reality is that collecting coordinates for every mailbox in even a small country would be crazy expensive. So what typically happens in most data sets (including Tiger and Navteq) is that the road segments get address ranges. There are size and cost tradeoffs in picking the size of those ranges. Typically an address range will span several blocks. The result of all this is that a program has available the coords of the end points of a road segment and that road segment is named "Maple street" and that it contains "odd addresses 1001-1399 on the north and even 1000-1398 on the south". If you're in an area that has houses exactly evenly apart and doesn't have an apartment or a park in there, it usually works well enough that you can drive to the extrapolated coords and start looking without thinking too much about it. Sometimes you'll be a couple of blocks off. The first resource above is provided by Locative Technologies. Their principles are Rich Gibson and Schuyler Erle. Those happen to be two of the three authors of Mapping Hacks. See the book link at http://mappinghacks.com/ and the TOC at http://www.oreilly.com/catalog/mappinghks/index.html . It contains sections on geocoding and many other topics that may be of interest to this crowd. It's really a nice introduction to electronic mapping and provides nice definitions and example of various projections, software, and techniques. It also contains several hacks that mention, use, or are predicated upon GPSBabel. (My favorite byte is at the bottom of page 226, "As befits a Swiss Army Chainsaw, GPSBabel has...") Within the next month or two, we'll see another book by that duo: http://www.oreilly.com/catalog/googlemapshks/ It, too, is likely to be found useful by the kinds of people that use GPSBabel - especially if you use Google Maps, of course. It has a couple of sections written by Ron Parker and myself. The final TOC for that one hasn't made it ot the site yet, but if you're a user of Google Maps or a developer, you're likely to find new rabbits to put in your hat. Sarbanes Oxley disclaimer: I get paid the same whether you buy the book or not. :-) RJL |
From: Beverly H. <Bev@BevHoward.com> - 2005-12-05 20:26:50
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>> geocoding is hard << Not complaining, just observing... it's a great resource despite it's limits an foibles and each new discovery significantly increases the power of my Meridian. Thanks also for the additional resources. Beverly Howard |