This article will discuss two topics in geo-referencing. First, we'll talk about how you geo-encode, or geo-reference, photos so that you can link them to a map. Second, we'll talk about how you display your GPS on a map and then link photos to particular locations.
Geo-encoded photos are photos that have location information stored inside of the image itself. There are essentially two ways to geo-encode, or geo-reference, photos.
The first method is to geolink location to the image on-board the camera. The advantage to this is that if the photo media become separated from the GPS log, the images contain location context as metadata inside the image header. Recently, Ricoh developed a device that has both a GPS and camera. The Ricoh Caplio Pro G3
has a number of excellent features: wifi, bluetooth, compact flash and SD card media, gps and a 3.24 megapixel camera with 3x optical zoom. GeoSpatialExperts GPS-Photo Link
software can be used in conjunction with the Caplio Pro G3 to organize photos and generate web-based reports on a PC. There is also an ArcGIS plugin to use the GPS-Photo Link software with ArcGIS. Photos are stored as JPEG images, text as TIFF, video in an AVI format and audio as wave files.
The second method of geo-encoding involves geo-linking on a PC by using a GPS log in conjunction with date-stamped digital photos. The GPS-Photo link software mentioned above can also do this, and thus be used in conjunction with a variety of GPS devices and cameras. The advantage to this is that you can use any GPS, camera and a multitude of software. Of course, the disadvantage is that should the images or track log become separated before downloading to a PC, images will lack location context. Additionally, users need to ensure that the GPS and camera are synchronized temporally since it is the time stamp that is used to link GPS location information to photos.
In general, JPEG images are preferred for geo-linking because EXIF is a JPEG image format and is widely supported by digital camera manufacturers. There is a variety of software available for writing to JPEG EXIF
headers. Excellent examples are RoboGeo
for the PC and the free GPS PhotoLinker
on the Mac. There is also photo editing software that also lets you to add location metadata in EXIF manually. For example, see iView Media Pro
for the Mac and PC.
Currently, you can use tools such as GPSBabel
to convert between various GPS formats on a variety of platforms. Sometimes you need to do this before using tools such as RoboGeo or GPS PhotoLinker so that your GPS log is in a format supported by a particular tool.
So now you've managed to geo-encode your photos. How do you now link them to a map? Some tools such as GPS PhotoLink give you an option to display on a map on the web using services such as TopoZone
. Both TopoZone and TerraServer
have web services but are limited to maps in the United States. Another mapping service, MultiMap
, is also popular in the United Kingdom and other parts of the world.
If you also want to display your track log on a map, you'll find that there is often a fairly complicated workflow involved. Phil Torrone describes
how he uses USAPhotoMaps
in conjunction with his Garmin ForeRunner 201 to create a view of his running route on a satellite map. USAPhotoMaps downloads aerial and topographic maps from Microsoft TerraServer
and plots the XML-based ForeRunner log on the map.
Another example of plotting a GPS log can be seen at the MacDevCenter
in an article by David Goldwasser where he describes using TopoFusion
for photo linking. TopoFusion uses maps from TerraServer as well as NASA's OnEarth server
. Visit David's site to see photo-linking in action
on his map-based track log. The workflow is quite complex in creating this site, but the demonstration illustrates the utility of combining location-based visual media in a web-based format. What is lacking is the ability to dynamically generate these views using tagging or semantic mark-up as well as an ease of use needed by mobile users.
For some exciting new directions in geo-linking, there is a flash photo blog
here where flickr photos are tagged with location and projected on a world map. Similarly, Tokyo Picturesque
is a project enabling people to upload their geo-located cellphone photos to a map of Tokyo. Also, BlogMap
aspires to use geo-coded blogs
and a map to show "neighblogs". BlogMap uses Microsoft MapPoint to map geourls. Now imagine that your personal device is a blog...
Finally, Google maps is inspiring a lot of creativity. Glen Murphy
has created a GPS interface to the XML-based Google maps. In a previous post
, we reported on Jon Udell's
description of an annotated multimedia google map (also at Engadget
). There are also some google map hacking sites emerging that are filled with useful information:
So now that we've geo-referenced photos... what about information about direction, azimuth, altitude, or distance? And what about video mapping? Well, there's not much use for this yet in consumer-based products. However, there are some high-end tools such as Red Hen Media Mapper
and SAIC GeoRover
that will do some of this. However, the workflow is still complex and the price point high. Again, looking toward the consumer hacker we may see new use cases for these technologies at an ease of use and affordability that may spark interest in commercial vendors.