Background: GPS and Geocoding

"GPS coordinates" is a commonly used term, but it mixes up two things which are not directly related:

The coordinate system defines degrees of latitude and longitude covering the whole surface of the earth:

• 180 degrees of latitude, beginning with 0 degrees on the equator, and ranging up to 90 degrees on the north pole (90°N) and 90 degrees on the south pole (90°S).
• 360 degrees of longitude, beginning with the zero meriadian, which extends from the north pole to the south pole and runs through the observatory of Greenwich (near London). Values range from 180°W to 180°E.

To get precise values, degrees are subdivided into minutes and seconds:

• One degree is about 111 km or 60 nautical miles on a meridian.
• One minute is 1/60th of a degree, which is 1.852 m or 1 nautical mile on a meridian.
• One second is 1/60th of a minute, which is about 31 m on a meridian.

The resolution currently available from the GPS system on non-military devices is about 10 meters.

Not so long ago, the idea of geocoding (or geotagging) needed to be explained. Today, almost everyone knows what it is about:

Providing image files with information about the place where the photo was shot.

A photo can usually be assigned a unique location, as every place on our planet can be uniquely described by geographical coordinates (latitude and longitude). With photos "knowing" their coordinates, there is a fascinating range of new options:

• You can arrange images by their location.
  The panorado image finder is able to retrieve images according to their distance form a specified location.
• Image locations can be displayed on a (digital) map or satellite image.
  panorado provides a button for launching the Google Earth client which will "fly" you to the image location!

As today's GPS receivers are small, cheap mass products, it's a manifest idea to integrate them right into digital cameras which can then save each picture's coordinates directly.

This is Ricoh's approach with cameras like the Ricoh Caplio Pro G3 which can be supplied with a GPS receiver module on a CF card.
Its successor, the Ricoh 500 SE, is scheduled for sale at the beginning of 2007.

Similarly, some high-end Nikon SLRs can be connected to an external GPS receiver which supplies coordinates in NMEA format.

GPS PhotoLink is a software solution. It's based on coordinates logged by a GPS receiver while pictures are taken. After the shooting, the software synchronizes the GPS log data with the image files using time stamps.

This is similar to the Sony GPS Tracker (GPS-CS1), a light-weight GPS receiver which is shipped together with software for geo-tagging photos from the positions of the recorded GPS track.

Without using any special hardware like in the examples above, you can use the Panorado 3.3 image properties tool to insert GPS coordinates (either manually, or retrieved from Google Earth) directly into an image file.

The EXIF standard provides a format for storing GPS coordinates within JPEG image files. This standard with precise specifications for coordinates already exists for some time, and certainly this feature will be used much more in the future.