Much depends on the accuracy you desire. Most of the free geocoders listed on that page are not worth much in that regard, compared to professional-level, licensed geocoding software or services.
As for batchgeocode.com, it uses the Yahoo API's geocoding engine. Yahoo sends precision flags and sometimes warnings with each address transaction, but batchgeocode.com discards those important data elements and just plots Yahoo's best guess. So some addresses will not be geocoded at all, others will be geocoded at grossly wrong locations, with nary a warning to the user. Yahoo seems to tolerate this use of its geocoding engine -- on its face an apparent violation of the Yahoo API -- so long as the batch geocoding is crippled by suppressing the warnings. That way, the intellectual property and market of providers such as Tele Atlas, which markets professional-level geocoding services, is fairly well protected. It's easy to see at least some of the precision warnings of Yahoo and Google -- by submitting one address at a time -- to a different third-party site: http://www.gpsvisualizer.com/geocode . If you want to see everything, you must use the APIs, which impose legal restrictions on their use. But do not expect to get decent geocoding for free. I suggest that you explore a commercial solution to geocode your batch of 15,000 locations. A professional geocoding engine will return, along with the lat/lon coordinates, specific fields denoting the precision and warn of ambiguities. Then you must set you quality threshhold, decide on a strategy to fix errors and resolve ambiguities, and design your own application to comply with whatever business rules you set. Achieving anything approaching 100 percent accuracy will almost certainly involve human effort to deal with exceptions. The error rate will also be a function of how well your input addresses are validated and standardized in advance. Garbage in, garbage out. On Oct 22, 2:14 pm, JF <[EMAIL PROTECTED]> wrote: > Thanks for this info! I tried many Geocoders listed > onhttp://groups.google.com/group/Google-Maps-API/web/resources-non-goog..., > but none of them seem to work for me. This is for a project located in > Canada, so already the set of Geocoders that can be used is reduced to > the ones providing data for Canada. Many links on that page refer to > Geocoding pages using Yahoo!'s geocoder, but yahoo only allows to use > its geocoding service if it to use the data in conjuction with Yahoo > Maps; we want to use Google Maps. geocoder.ibegin.com, which is listed > on that page, seemed to offer an interesting solution, however it > could not locate my place properly (right street, but wrong city!). > > We have a database containing Latitudes and Longitudes for all postal > codes in Canada, and I can use that. However, full addresses > geolocalization gives better results, especially for remote places > where postal codes cover a large area. > > We have an interface on our Intranet that allows us to enter new > locations in the database driving our web site. What I would like > would be to have the possibility to geocode a location when that place > is saved in our database, and to save the latitude and longitude at > the same time. It would be easy to do this we Google's geocoder, but I > am not sure whether this would infringe its terms of use. I would > really appreciate getting feedback from Google about this. > > JF > > On Oct 22, 11:36 am, mapperzUK <[EMAIL PROTECTED]> wrote: > > > > > JF as noted by Pamela Fox in the Tutorial -'Using PHP/MySQL with > > Google Maps' > > > "Note: This tutorial uses location data that already have latitude and > > longitude information needed to plot corresponding markers. If you're > > trying to use your own data that don't yet have that information, use > > a batch geocoding service to convert the addresses into latitudes/ > > longitudes. Some sites make the mistake of geocoding addresses each > > time a page loads, but doing so will result in slower page loads and > > unnecessary repeat geocodes. It's always better to hardcode the > > latitude/longitude information when possible. This link contains a > > good list of > > geocoders:http://groups.google.com/group/Google-Maps-API/web/resources-non-goog... > > " > > >http://code.google.com/support/bin/answer.py?answer=65622 > > > so if you pre-geocode your 15,000 locations into a database then you > > will achieve your option 2. > > > (but never trust a geocoder - Mike > > Williams)http://markmail.org/message/ryz24bm7n66ew6b5 > > > Mapperzhttp://mapperz.blogspot.com/ > > > On Oct 22, 4:17 pm, JF <[EMAIL PROTECTED]> wrote: > > > > I have the following problem. I am working on a web site backed by a > > > database containing around 15 000 locations. These locations can be > > > displayed on maps on the web site. On these maps, other surrounding > > > locations should also be displayed. In the end, around 50 locations > > > could be displayed on a single map with its main point of interest. So > > > before displaying the map, around 50 locations will need to be > > > geocoded in order to position them on the map. The geocoding requests > > > would be issued by the server, which seems to be a problem. Imagine > > > that 10 people are surfing the site and viewing maps at the same time, > > > it would mean that the server would need to geocode 500 locations in a > > > short amount of time. This is a problem, since Google's geocoding > > > servers stop answering when too many request are coming from the same > > > location all at once. > > > > I see two solutions: > > > > 1) The geocoding should be done on the client side. However, in most > > > Google Map examples, the latitudes and longitudes are provided by the > > > server. Is there somewhere a good example in which latitudes and > > > longitudes are fetched by the client just before displaying the map? > > > > I see a drawback with this technique though. It does not reduce the > > > load on Google's geocoding servers. > > > > 2) A better technique would be to cache the geocoding data (latitudes > > > and longitudes) for the 15 000 locations on the server beforehand. > > > This appears to me as being much cleaner, and it removes some burden > > > from Google's geocoding servers. What is the point of geocoding the > > > same locations multiple times anyway? > > > > However, there seem to be a legal issue with this second technique. > > > Onhttp://maps.google.com/help/terms_maps.html, one can read the > > > following: > > > > <blockquote>Also, you may not use Google Maps in a manner which gives > > > you or any other person access to mass downloads or bulk feeds of > > > numerical latitude and longitude coordinates.</blockquote> > > > > This appears to make the second solution illegal, which is really too > > > bad. I would like to get a confirmation of this though from Google > > > staff. > > > > Cheers! > > > > JF- Hide quoted text - > > - Show quoted text - --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google Maps API" group. 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