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What does latitude and longitude of place such as state or country place represent ?Is it centre?  XML
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sanketku



Joined: 12/09/2016 07:34:15
Messages: 5
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Hi,

What does latitude and longitude of place such as state or country place represent ?Is it centre of the place? If yes, how is the centre obtained? Is it the centre of bounding box for the place?

Please suggest.

Regards,
Sanket
JOleg



Joined: 22/01/2017 01:02:39
Messages: 6
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Maybe if you tell us the reasoning behind the question you'd have more chances of finding out the answer. I wondered about this too, sometimes, but only out of curiousity. Just did a quick random test on Google maps, at least visually it does seem like a center of the bounding box. But that's only visually. As for me, that does the job, I wouldn't expect anything more. If I say give me the location of Australia, I implicitly mean a single point, not a bounding box and not a capital, just a point which is inside the requested region, for quick search purposes. Would I want to give me a more exact location I would have asked for a more specific toponym. I just can't think of a case where it would really matter what the latitude/longitude point represents.

On the other hand, and what may not be clear, is, for instance, when I pass on the function 2 lat/lon points and I want to find out the distance between them, say in kilometers. And the function does give me the distance. But my questions would be:

1) does it calculate it based on imaginery straight line or it takes into account the existing roads? If it's the later, then the distance would be significantly longer. And if it's the later, which roads does it take, shortest, or using major/international roads...
2) does that take into account the elevations? cause if yes, that adds up to the distance if there are many "serpentine roads" (in the mountains)

and so on.

So, for approximate needs, whatever the value of the official (or from mature trusted source) latitude/longitude point is, it should be fine.

Unfortunately this isn't an answer to your question, but I thought I'd give some thoughts to elaborate further.
sanketku



Joined: 12/09/2016 07:34:15
Messages: 5
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Hello,

I tried checking few places such as British Columbia, Alberta by searching in Google Maps by given coordinates of these places. It seems that for majority of places, given lat/long in geoname is the centre of bounding box of the place but for places like Alberta, the given lat/long (52.28333 , -117.469) is not the centre of BB.

Could you please clarify what is the lat/long for a place means here. Is it the centre or something else?

Regards,
Sanket
sanketku



Joined: 12/09/2016 07:34:15
Messages: 5
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Thank you for replying.

I want to construct the bounding box for a place using the centre information of the place, points in geonames under the place and area. So having precise centre information or at least information about what does the lat/long of point represent and how it is obtained, will help me to make further decision.

Thanks,
Sanket
saphir



Joined: 05/06/2010 22:44:39
Messages: 129
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Hi Sanketku

That does not work.

A bounding box is a theoretical construct on the earth’s sphere; its surface would have no meaning. Boxes of neighboring countries most often overlap.
The box is a spherical isosceles trapezoid… you cannot transform a curved surface (the earth) into a flat surface without distortions!
The center of Norway’s box is far away, in northern Sweden. The box center of island nations is most probably offshore; e.g. for New Zealand it is in the Tasman Sea.

The geographic center of a territory is calculated with an enormous quantity of small partial surface areas. It returns a geographic point with strictly no useful meaning, besides making some otherwise unknown villages a bit happier.

To create a bounding box out of GeoNames, you can search the database for the most western, eastern, northern and southern points of the given entity. However, if the extreme points are not otherwise significant, they are probably not in the database.

Otherwise, go to Google Earth, display the borders and the geographic grid, and you will easily detect the extremes.

Cheers,
Urs
 
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