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  • Status: Solved
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LATITUDE AND LONGITUDE

Hello,

How do I add, and substract 1 mile for a given latitude? And 1 mile to a given longitude?

Thanks!
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SimpleDude
Asked:
SimpleDude
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2 Solutions
 
d-glitchCommented:
Latitude is easy.  Longitude is more complicated.

    http://www.answers.com/Q/How_many_miles_are_in_a_degree_of_longitude_or_latitude
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ozoCommented:
latitude + 0.014457
longitude + 0.014481/cos(latitude)
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d-glitchCommented:
And you need to be careful at the boundaries:  the N and S poles, the equator, the prime (0 deg) meridian and its opposite (180 deg).
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SimpleDudeAuthor Commented:
Hi guys, I just need to select X number of records within a Lat and Long range.

I was using this formula, but it drastically decreases the server performance:

  (ACOS(SIN(47.988594 * PI() / 180) * SIN(dbo.ADDRESSES.latitude * PI() / 180) + COS(47.988594 * PI() / 180) * COS(dbo.ADDRESSES.latitude * PI()
                      / 180) * COS((- 122.201789 - dbo.ADDRESSES.longitude) * PI() / 180)) * 180 / PI() * 60 * 1.1515 BETWEEN 0 AND @distance
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d-glitchCommented:
How big is the data base?  Is it sorted in any way?
What units are used in the database?  Degrees or radians?
You should search in the same units the data base uses.  Save a lot on conversions.

This   (SIN(47.988594 * PI() / 180)  (and several similar terms) are constants.  
You only have to calculate them once.

Is this related to the nearest k restaurants problem?
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SimpleDudeAuthor Commented:
Something like that. The point of origin (lat-long) changes constantly, that's why I cannot calculate it just once.
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ozoCommented:
If the restaurants are in a small area, it may be preferable to convert the latitudes and longitudes into a flat grid to make distance calculations easier.
If the restaurants are in a large area where a flat approximation would be inaccurate, it may be preferable to convert into a 3-d orthogonal coordinate system to make distance calculations easier.
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SimpleDudeAuthor Commented:
Thanks guys
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