Latitude and Longitude

Finding Latitude and Longitude Using Your Cell Phone

The GPS feature of our cell phones works without the Internet.  The latitude and longitude will be accurate because the phones calculate them based on signals received directly from the GPS satellites. There are at least three ways to obtain latitude and longitude from a smartphone:

Using Google Maps.  If you find your location using Google Maps on an Android phone or on an iPhone you can find your latitude and longitude by doing a long press at your location.  This will usually cause the app to display the location in the search field using Decimal Degrees format with 6 digits to the right of the decimal point.  Google Maps won't display a detailed map if the Internet is not available unless you ask it it to save its map before the Internet goes down, but the GPS coordinates will be accurate anyway.

Using Solocator.  Solocator is a specialized camera application available on both Android phones and iPhones.  It can be used to take photographs that have the GPS location displayed at the top of the photograph using Decimal Degrees format with 6 digits to the right of the decimal point.  For this reason, you may find it a convenient way of obtaining your location by taking a photograph with the application.

Using a GPS app.  There are a variety of GPS applications available for Android phones and iPhones.  One such app that is available for Android phones is “My GPS Location” by Digrasoft.  It reports latitude and longitude with 5 digits to the right of the decimal point. There’s also an app for iPhones called GetLocation.

History of Formats for Recording and Reporting Latitude and Longitude

Degrees, Minutes and Seconds

Recording a location by latitude and longitude has a long history associated with the history of navigating at sea. Traditionally, latitude varies from 0 to 90 degrees north or south with each degree divided into 60 minutes and each minute divided into 60 seconds.  Note that these minutes and and seconds have nothing directly to do with time. Exactly 0 degrees latitude is associated with the equator. In contrast, longitude varies from 0 to 180 degrees west or east with 0 degrees corresponding to the longitude of Greenwich, England. As with latitude, each degree of longitude has been traditionally divided into 60 minutes and each minute into 60 seconds. Longitudes east of Greenwich are referred to as east (E) latitudes and those west of Greenwich as west (W). This system is referred to as sexagesimal or DMS format.

Degrees and Minutes

Modern nautical charts usually omit seconds and use fractional minutes instead. In place of seconds the minutes part of a latitude or longitude is expressed by adding digits to the right of the decimal point.  For instance, a latitude might be expressed as 45 degrees, 29.32 minutes North. One reason for this convention is that one minute of latitude is almost exactly one nautical mile.

Decimal Degrees

With the advent of computers and GPS satellites, dividing degrees into minutes has become less common. Instead, latitude and longitude are expressed as degrees with many digits after the decimal point, for instance 45.471687 N, 122.728182 W.  Finally, the North (N) or South (S) is often left off the latitude in favor of using positive numbers for latitudes north of the equator and negative numbers for south of the equator.  Similarly, longitudes west of Greenwich are often reported as negative numbers and those east reported as positive numbers. This format where only positive or negative degrees are reported is referred to as Decimal Degrees. For example, 45.471687, -122.728182.

Converting Between Formats

The history summary above may be somewhat interesting but it leads to many ways of reporting latitude and longitude.  Because most of the tools we have at our disposal use Decimal Degrees, we will use that format for our exercises. If you find that the app you are using produces a different format, you can convert that format to decimal degrees. For instance, the FCC provides a web page that converts between degrees/minutes/second and decimal degrees. You may need to add the negative sign to the longitude, however, assuming you are converting a location in the western hemisphere.

Voicing Latitude and Longitude

For clarity begin with the word “latitude” followed by the latitude in degrees. (Think of “Latitude” as a proword that you use instead of “Figures”. Give 5 or 6 digits to the right of the decimal point for each number. The decimal point should be voiced as “decimal” rather than “point”.  Then say the proword “longitude” followed by the longitude as a negative number because you are west of Greenwich, England. For instance, “45.471687, –122.728182” would be voiced as “Latitude four five decimal four seven one six eight seven Longitude minus one two two decimal seven two eight one eight two”.  (Notice that you can leave out the comma.)