Skip to main content

Why this difference?

       Several of you must have observed this like I did, that the Google geocoder returns different results on the Google Maps website and Google Maps API v3 for the same address string. To understand why this difference exists, I dug deeper into the web and came up with the following.

       The first and foremost place to look for an answer was the Google Maps API FAQ section. The FAQ section did not let me down of course! The FAQ section says:
The API geocoder and Google Maps geocoder sometimes use different data sets (depending on the country). The API geocoder occasionally gets updated with new data, so you can expect to see results changing or improving over time.
        What I concluded from the above is that, in a lot of cases Google licenses data from other companies like DigitalGlobe, Infoterra Ltd & Bluesky, GeoEye, Getmapping plc, Tele Atlas, etc. When negotiating a licensing agreement for copyrighted map data the two companies have to come to a mutually satisfactory agreement. In some cases, a company might be willing to license data for use in regular Google Maps but not through the Google API. For example, in the UK you have to buy a license to access the post code (Zip code) to longitude/latitude database. Google has precise info for regular Google Maps, but if you do the same query through the API you get a much less precise longitude/latitude. Why? Well if you are the company with the post code to longitude/latitude database and you currently charge people for access, then Google starts giving away access for free, probably no-one's going to want to pay you for access to it any more. So you'd only agree to let Google give away your product for free if they gave you at least as much money as you make by charging for the product!

       Though this is a pretty good conclusion, but then I could see people who have posted several instances on different forums of the same address getting geocoded differently...So I started verifying. One address and an explanation appealed to me and I am sharing it here!

       The address to be geocoded was "brussels (municipality)". Now this address geocodes to "City of Brussels Belgium" through the Google Maps website, whereas using the API returns "Brussels City somewhere in the Philippines". Now, consider the address "brussels (This is a nice place)". This string returns the same address in both - the Google Maps website and Google Maps API v3. Assuming that Google geocoder does not consider the contents in the brackets, then how come "brussels (municipality)"  is geocoded differently?

      Well I couldn't answer this one and so decided to throw this question to all you guys and gals reading this. Could you give a possible explanation?

Comments

  1. Why do you track the location of your visitors without asking them for permission?

    ReplyDelete
  2. @Pil
    You might want to consider unplugging your network cable.

    ReplyDelete
  3. Hello Blog Readers. I am posting in this comment the response that I received from a member - Rossoko; in the Google Maps API v3 forum.

    "The API geocoder is a postal address geocoder. Things like "brussels (this is a nice place)" are not well-formed postal addresses, and the geocoder struggles with them. You do have to look at all the results returned, not just the first one. They may not be in the order you expect.

    The geocoder at maps.google.com extends its search to business and
    institution listings and so on. It's much more likely to come up with matches against things like resteraunts in Brussels, BE, to help it along. This is a convenience for the non-programmer user.

    If you want API behaviour to include non-postal addresses you need to
    incorporate other services yourself, the programmer has the option.
    For example, if you want results for things like city or province
    names, the postal address geocoder is not really the right tool. Look into Geonames or similar specialised services."

    ReplyDelete

Post a Comment

Please leave your comments here...

Recommended for You

Is Google cheating?

               I found this piece of interesting fact, accidently while browsing the internet. Google shows different maps for India, China and USA. Confused hun! Well don’t be…Just read on… In Indian version of Google Maps, you can see Arunachal Pradesh and eastern part of Jammu and Kashmir as integral part of India. In US version of Google Maps, you can see Arunachal Pradesh and Jammu and Kashmir as a disputed region. In the Chinese version of the Google Maps, you can see Arunachal Pradesh and JnK as not a part of India.                 Many people complained this issue to Google. A Google employee responded : “ We do show different versions of this border, because we required to by law. Indian law requires us to show it one way, and the Chinese law requires us to show it another way . If we can legally do so, we strive to present borders in a neutral and objective manner, which is why the US version avoids taking either side and simply labels the border as disputed. ”   

Custom online cards from Google Maps...

            Share a message of holiday cheer with custom online cards from Google Maps this New Year! Think Green, Go Green this New Year. Save paper and that too with a difference! This new year you can send your friends, family and loved ones an e-card which is out of the box!             You can choose from 10 different online holiday cards and add your personal message. Now, after reading this you will think what's so different here! The surprise is yet to unfold...You can include specific directions, a Street view image or your favorite place on the inside of the card!             So now planning your New Year party will become easier. You can send an e-card with directions from your friend's place to the place where you are hosting your New Year party! Won't that be fun!             You can send your personalized Google Maps New Year Cards from here !             Warm wishes for a great holiday season and wish you a Happy Mapping Year...

Map Loading...

    The blank web page seems so boring and dull when the map is still loading. You will come across such a situation quite often where you will be having a slow internet connection! We cannot do anything about the slow internet connection, but we can surely avoid the dull blank web-page by using a simple trick. We can place a "loading" image at the center of the web page so that the page doesn't look blank! An image like this:             The following code will show you how this can be done and here it is!     As you all can see the code is very very simple and the output will look as seen in the results section above. The image below shows the loading stage of the map.       Do let me know what you think about the examples shared here! Do leave your comments here! Till the next example, happy mapping!

GIS Technology to identify all properties in BBMP Limits

          The Bruhat Bangalore Mahanagara Palike (BBMP) has for the last two years, been in the process of conducting a massive exercise to map the 13.87 lakh properties in the 198 wards in the city. Geographical Information System (GIS) has proven to be an effective tool for analysing and displaying thematic maps of all the roads for proper evaluation and correction of zones.            As of now, 11 lakh properties have come under the tax net. The aim of this programme, which is perhaps the first such exercise being conducted in the country on such a large scale, covering 800 square km, is to bring all properties under the tax net and ensure that the BBMP has accurate information pertaining to the properties’ dimension, built-up area, land use and classification. The process of validation of GIS maps will be completed in January 2011.           The process uses satellite digital maps of the BBMP area to generate a vector map from the information obtained. These high r

The mystery of the "Vanishing Island"

    A 60 square mile land mass know as the Sandy island or the Sable Island has vanished without a trace from the Pacific Ocean. This island was supposed to be located between Australia and New Caledonia and can be seen in the older versions of Google Maps and several other scientific and nautical maps. The original location of the Sandy Island     Just recently a research vessel sailed to the location to find nothing but deep blue Pacific more than 4,500 feet deep. The researchers and doctoral students overboard the ship saw this mysterious island on all the scientific maps and weather maps but not on  one  navigational chart that was on their ship. There was no indication of any land mass at the exact location where the Sandy Island was shown.     If Sandy Island did exist, it would sit in the French territorial waters. But the French government denies that any of its official maps ever listed the invisible island. If such an island never existed, how did it find its way on