Mapping: About your latitude and longitude

It’s been a long time since grammar school for me. And I’ve forgotten a lot. For one thing, I recently discovered couldn’t find things on a map by latitude and longitude.

I’ve been working with Google Maps a lot in the last year. When you visualize location information you really need the latitude and longitude of a person or thing. Here’s one way to keep them straight. When you think Longitude think about the "long" part of the word. It helps me because when I think of length and width, I picture length going up and down and width going side to side. I’ll explain in more detail.

Lines of Latitude run east to west on a map ringing the globe parallel to the equator. Similarly, lines of longitude start at the North Pole and ring the earth at the South Pole. So, longitude is to length as latitude is to width. Some more facts:

Maximum value of Latitude is 90 degrees (at poles)
Minimum value of Latitude is 0 degree (at Equator)

Maximum value of Longitude is 180 degrees ( eastward from Greenwitch, England)
Minimum value of Longitude is -180 degree ( westward from Greenwitch, England) (courtesy Yahoo Answers)

So for example, when I watch CNN now, during this Gustav hurricane coverage I can understand the position better. The longitude at 4PM today was 87.3 west which is about halfway to the 180 point on the opposite side of the globe from England. The latitude of the hurricane was 26.4 North or a third of the way to the North Pole from the Equator.

If you are looking to find a location, there are plenty of tools. For named places you can use the Geonames.org database of named places to provide a tool to find latitude and longitude coordinates. This is especially useful in a disconnected or limited connectivity environment. Once the database is downloaded, you no longer rely on a network connection to retrieve location information.

If you do have a reliable internet connection, as many of us do at home or work, plenty of tools exist to help get that location information we may need. if you are a javascript wiz or have access to one, the API’s for all of the major map providers have functions you can use for looking up addresses to return coordinates. This lookup is commonly referred to as Geocoding.

There are also tools for the everyday internet user. For me, the easiest demonstration is my twitter profile. It shows my location because I sent it from the Twitterific app on my GPS enabled iPhone. Not everyone has a network connected GPS, but this is becoming more common.

Maporama.com is a site I just found today, but maps zipcodes and addresses with the coordinates displayed on the page.

One more example is from Google Maps. After mapping any business or home, you can find the coordinates in the email link popup after the ll= part.

Last but not least, some sites provide geocoding based on your internet IP address. One example of a site like this is ip2location.com. This is a technique used on some websites. For example, Google targets ads at you on its search pages by looking at your IP address. As you can see from the screenshot, this method of geocoding was the least accurate of the four methods I demonstrate here.

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