Administration: Omnidex Features

Geographic Searches

Latitude and Longitude

The universal method of identifying a location is by geographic coordinates, specifically latitude and longitude. Latitude measures the distance north and south, with the Equator being the central latitude. Longitude measures the distance east and west, with the Prime Meridian being the central longitude. A set of latitude and longitude coordinates can identify your exact location on the planet.

Databases are tracking latitude and longitude coordinates with increasing frequency. Some applications limit their use of this capability to recording the geographic coordinates of their branches, or even just the central point of a zip code, called the centroid. More and more databases record the geographic coordinates for every specific address in the world. Geocoding services allow companies to submit any address in the world and get back the geographic coordinates for storing in the database. As technologies develop, expect more and more databases to include detailed geographic coordinates.

Technological advances are bringing GPS capability to mobile phones and cars, and so transaction databases often contain the exact location where the transaction occurred. When an email is read, or a web search is done, or a product is purchased, it is possible to know where the user is. Social networking services will tell you who among your friends is near you, and restaurant services will tell you where to find good food around the block. With all of this geographic data, it is becoming increasingly important to search based on latitude and longitude.

Geographic coordinates can be specified using two main approaches. The first approach shows degrees, minutes, seconds and hemispheres, and is the original approach used in early navigation. There are 180 degrees in a hemisphere, with 60 minutes in a degree, and 60 seconds in a minute. (Note that these minutes and seconds are measurements of a sphere, and not measurements of time.) The second approach uses decimal figures to show degrees, and fractional portions of degrees. The latter approach is often easier to use in basic computation. Omnidex supports both approaches to representing geographic coordinates.

Latitudes and longitudes differ in an important way. Lines of latitude are parallel, since they represent horizontal “slices” of the earth. As such, the distances between lines of latitude are always the same. Lines of longitude are not parallel. They are widest at the Equator, narrow as they approach the North and South Poles, and all converge into the same spot at the exact North and South Poles. As such, the distances between lines of longitude vary greatly. This requires more sophisticated mathematics in order to calculate the distances between two points.

Additional Resources

 
Back to top
admin/features/geo/latlong.txt · Last modified: 2016/06/28 22:38 (external edit)
 
 
chimeric.de = chi`s home Valid CSS Driven by DokuWiki do yourself a favour and use a real browser - get firefox!! Recent changes RSS feed Valid XHTML 1.0