Postcodes and sounds as matching

[Buffy Beagle]

I've always been surprised how slow TTN is at searching for addresses. In particular, I don't understand why there should be any noticeable delay at all in looking up town names, even if access to the memory card is a bit slower than it should be. With decent indexing, surely a lookup on a list of less than 100,000 town names should be pretty instantaneous with a 400MHz processor?



The TTN2 FAQ on the TomTom website (http://www.tomtom.com/support/ce/support/navigator2.php)says, amongst other things:



"Beta testing proved that the 3-character alfanumeric codes available did not save time compared to typing in the first three letters of a city, and in fact conflicted with our spelling-correction and "sounds as" technology."



Is the speed problem with looking up town names, etc. perhaps that TTN2 waits for the results of its fancy "sounds as" matching before it reports any results? If so, wouldn't it be better to make a preliminary report of exact matches first, before proceeding to more complex fuzzy matches?



Perhaps we UK users would happily sacrifice sounds-like matching if that meant we could have proper postcode lookups. As I've observed before if Ms can do postcode lookups in Autoroute and if it can be included in a route-planning program given away on magazine-cover CD, surely TT ought to be able to rise to the challenge! Alternatively, if TT can't perhaps the author of GPS Assist could (please).



Hugh

[Dave]

It really depends on what file format they're using, whether it's a flat file, eg like a text file but in a different format, or whether it's database driven. From what I've seen it is database driven, but I agree it does take a long time sometimes searching for addresses, I think it could be much quicker looking at other products on the market.



Postcode lookups is definately possible on the Pocket PC, TravRoute do this quite happily and have done for years, it's the way TomTom have implemented it. Judging by the fact that TomTom were ready to release Navigator 2 with postcode lookup, it appeared to be that they thought they could do it, but probably didn't quite realise the scope, because European postcodes tend to be numerical and not alpha-numerics, which for them is easy to do, and they probably have their database formatted in a particular way to cater for this kind of lookup.



Cosmetically adding postcode support to the UK version is probably quite simple by putting another search box on screen, or a combo/search box. However, if the way their data is formatted is to optimise it for European postcode lookups, then this might cause problems, and would have to be totally redesigned, and not make it into the current product. This I think is what has happened. Although postcode support partially is there, (eg 3 chars) not 4, I don't think it's possible to bring it in via program updates, and I suspect this is why TomTom have recently changed their FAQ's on this.



This will I'm sure bring a bit of a rebellion from UK TomTom users who purchased Navigator 2 in good faith because the advertisement information on TomTom's website and press releases did mention that UK postcodes would be supported.

[Buffy Beagle]

Surely it must be database driven, and if it is and the indexes have been properly constructed then looking up towns and streets should be very swift.



Regarding postcodes, shouldn't it be easy to tack on the ability to show a particular postcode location on the map?



You would need a postcode data file, which would provide geographical coordinates for every postcode, and a licence to use the data. However, that surely can't be a big problem since so many programs do postcode lookups already.



A cursory inspection of the TTN SDK help file lists a function called ShowCoordinateOnMap which takes longitude and latitude as parameters; this suggests that instructing TTN to move the cursor to a given latitude/longitude should be very straightforward. So, for someone armed with a postocde database as well as the SDK it ought to be a cinch to program a TTN add-in to take a postcode as input and instruct TTN to move the cursor to the appropriate lat/long.



While you were about it, tacking on the ability to handle grid references in the same way would be trivial, since you wouldn't need a grid reference database, just the readily available formulae to convert grid references into lat/long.



Obviously this would not be seamless integration, but it wold be a lot better than what we have (i.e. no postcode or grid reference lookup at all.)



I'm not offering to do this myself, since I'm not a professional programmer, but perhaps there is someone out there who would like to rise to the challenge!



Hugh

[Dave]

Writing this from the ground up would take an immense time, how many different postcodes are there in the UK that drill down to 5 chars, as this is really what you'd need, pref 6 if you wanted to be accurate enough to find one side of a street.



It's certainly possible for someone to write this, but it's certainly not for the faint hearted, and I really don't think anyone would jump to the challenge on this one. Really it needs TomTom to rectify this, and it may be down to them not getting the complete set of postcodes out of the geodata provided by TeleAtlas. It's a shame for TomTom, because we're already seeing a turn to CoPilot because many new purchasers are looking for searchable postcodes, and this now is something TomTom cannot provide.

[Buffy Beagle]

I've been googling around, and all roads seem to lead back to the Royal Mail who publish various data files. The most relevant format for the sort of use I described earlier in the thread is called "Postzon"; this gives a grid reference for every postcode in the UK.



There are at least two problems. One is the cost of licensing the data, which can run into £000's depending on the accuracy of the grid references and the number of users. It looks as if only a professional organisation assured of making significant sales could afford to use the data. The other problem is the file size. There are about 1,600,000 separate postcodes apparently and the file runs to over 65Mb. Presumably programs like Autoroute must find a way of compressing the data. I wonder how.



Hugh

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