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Comment by sgnelson | Hacker News Reader

Wow, I had no idea that Geocoding was so big around here, nice to see. So a question for all of you geocoders, how are you testing and determining accuracy? ie, how many "failed to geocode records" out of an arbitrary number could I expect given that the address is properly formatted?

By the way, (again, at least for the US), the best (fastest, very accurate) geocoder I've ever used was created by Alteryx. I've always been curious if it's actually their own geocoder, or they are using another service in the background. (edited to add: though of course, this is for Alteryx's proprietary system, and though it provides decent ways to get the data in/out, it's not simply a plug and play system if you're writing your own software.)

ESRI's is one of the worst; relatively slow, not all that accurate and worst of all (at least this was the case) it'll choke on anything over 300,000 records.

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Hi, co-founder of the OpenCage Geocoder here.

I can't speak to the opinions of others, but for me your question is a lot like asking "what's the best programming language?" The only realistic answer is that it depends on your task. We're continually facing new customer requirements, and what one customer thinks is absolutely essential, the next guy couldn't care less about.

A good example is speed. For some clients every millisecond is critical (imagine real time bidding systems), for others they are running a batch process to geocode their database in the middle of the night and couldn't care less if it takes one hour or two. Likewise huge differences in requirements in terms of accuracy. Some clients will accept only perfection, meanwhile the next guy intentionally wants a vague answer so that consumer privacy is maintained. Then obviously there are big differences across countries, forward and reverse, etc, etc. Some clients must have the attributes that using an open data source like OpenStreetMap allows, others care only about price.

So there is almost certainly a perfect answer for your specific geocoding needs, but there is no perfect geocoder.

Thanks for replying, your data sources are amazing, it must have taken quite a bit of work to put them all together.

And I get that different users have different needs, but I'm still curious about the accuracy (it's geography after all, I don't care how fast the results are returned if they're wrong.) And especially given the multi-data sets that OpenCage uses, how do you know that you're returning the right results? (obviously there is the spatial aspect, ie, within 100 yards of the true location; but I'm most curious about the percentage of returned address with a greater than 90% probability of being the "correct" address.) I wouldn't expect it from most geocoder services, but that's what "ground truthing" is for.And what happens if you happen to come across conflicting results when you're using the multiple data sets?

So again, all these new geocoders provide some nice services, but how are they measuring their accuracy of results? I could also shrink this question down to a business question, what makes your service better versus all the others? Who can prove to me that they provide the "best" (most accurate) results? (I'm not in the market, sorry, it's a hypothetical.)

I still think you're putting to much weight on accuracy as the key feature. We have plenty of customers who only care about having the correct town or postal zone or neighbourhood, and some even who actually do NOT want accuracy (due to privacy implications).

Nevertheless, yes of course I get what you are asking. Fundamentally all geocoders rely on someone having verified the input data, be it a government surveyor, a car taking pictures that are then evaluated (by humans and/or image processing software) or an OpenStreetMap volunteer, etc. We are at the end of a long data chain and have to trust the inputs we get.

In my 20% time I'm working on a world map at 1:1 scale which will solve this problem, hoping to launch next quarter ....

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