Background: GPS and Geocoding
- for photos!
What are GPS coordinates?
"GPS coordinates" is a commonly used term, but it mixes up two things which are not
directly related:
- Geographical coordinates - a reference system for uniquely
identifying any place on our planet.
- GPS (Global Positioning System), a technical system of the US Department of Defence.
GPS receivers can determine precise geographical coordinates from the radio signals sent by special satellites.
GPS was the first system available for this purpose.
Newer systems like Galileo, GLONAS, or Beidou are working very much alike.
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.
How is this related to images?
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 visualizing the positions of your photos on an interactive OpenStreetMap page.
How do coordinates get attached to pictures?
Today's GPS receivers are small, cheap mass products. That's why it is a manifest idea to
integrate them right into digital cameras which can then save each picture's coordinates
directly.
A large variety of GPS-enabled cameras from all major suppliers is now available,
in all price ranges, with a built-in GPS receiver.
Most smartphones are also equipped with a camera and a GPS receiver.
Without using any special hardware, you can use the Panorado 5.0
image properties tool to insert GPS coordinates (either manually,
or from the Windows clipboard) directly into an image file.
The EXIF standard provides a format for storing GPS
coordinates within JPEG image files.
