Geotagging Source Photos
For those taking photographs alongside their GPS unit, it is often useful to geotag the images. This means that the location where each photo was taken, is written into its EXIF header.
Doing this acts as an excellent source record when tagging data in OSM using photograph information. JOSM can display photos with an existing geotag and also write new tags to photos from a track log. For more details about using photos for mapping, see Photo Mapping.
How to write the location into the photo
There are a few different ways:
- Record a GPS tracklog and then use software to calculate the photo's position from the tracklog
- Use software that allows the manual editing of the photo's location
- Use software that allows you to manually select where the photo was taken using a map (this is probably not suitable for openstreetmap use due to copyright problems).
- Use a GPS-enabled camera (or camera enabled GPS/smartphone) - convenient but expensive
Geotagging photos from a GPS tracklog
The easiest way is to use software that calculates the photo's position by using a corresponding GPS tracklog and most OSMers seem to use this method. It will get a time and date from the photo, and work out where you were standing at that time using the tracklog.
It is necessary to correct for clock errors in the camera by synchronising with the gpx file. You can do this by:
- Trial and error;
- Take a picture of your gps displaying the time;
- Set your PC or Mac to sync with an atomic clock and then take pictures of the computer's clock.
- Set once a waypoint at the same time you take a photo => photo and waypoint must match (time shift can be found out between GPS and camera). E.g. geosetter supports this method.
- Take a photo at a known point, and match this manually - then the time difference can be calculated
It makes life easier if you set your camera's time to UTC, the same as that used in GPS signals; or, if possible, to set your GPS receiver to your local timezone.
Some articles on geotagging of photographs can be found at kowoma.de (german only, sorry). The articles describe some background of geotagging and introduce some programs for geotagging.
An incomplete list of geotagging software follows:
- GPicSync (Windows) (GPL v.2)
- WWMX Location Stamper 2.2 (Windows)
- gpsPhoto (Perl, command line tool)
- GPS-correlate (Linux) (GPL v.2 or later)
- GeoSetter (Windows)
- gpsphotolinker (Mac OS X)
- digiKam (digital photo management application for KDE)
- BT747 (Windows, Linux, Mac OS X (Java application))
- geotag (Java) (GPLv2+Public domain+"a BSD license"+"modified BSD"+LGPL+Freeware)
- Prune (Java, GPLv2)
- JPhoto Geo Tagger (Java, command line tool)
- JetPhoto Studio (Windows, Mac, commercial with free version)
- GPSClipper (Android app. updates Picasa web photos from GPS data track on the phone/tablet)
- Mappero Geotagger (Linux, Mac OS X, Windows, graphical with GPX correlation) (GPLv3)
- Garmin BaseCamp (Windows, Mac OS X)
GPS-enabled cameras / PDAs
Some (not many!) cameras give you the option to use an internal GPS device or connect to an external GPS device and geotag photos as you take them. Unfortunately for most budgets these are generally more expensive prosumer or professional cameras.
- 3G and newer models automatically geotag photos using GPS or cell tower location.
- Some HP iPaq PDAs have a built-in camera and GPS unit, for example the HW6965. With some configuration it is possible to both record a tracklog and geotag photos. It is great for incidental use but for taking lots of pictures the camera is very slow in both taking and storing photos, there is no zoom for taking street signs and the quality is very variable as it does not register light well.
- Nikon are the pioneers in good quality GPS-enabled DSLR cameras: D1H, D1X, D2H/Hs, D200, D2HS and D2X/Xs, D3, D300 Digital models. They don't make it cheap though. You'll probably need to hack your own RS-232 cable or spend about US$95 on an Nikon MC-35 GPS Adapter Cord and probably still do some hacking to interface it with an RS-232 GPS device. Example The Nikons record only latitude, longitude, altitude, GPS time, and heading (with some models).
- The Coolpix P6000 point-and-shoot has a built-in GPS receiver.
- Dawntech offers complete hot shoe GPS solutions for D2H/Hs, D200, D2HS and D2X/Xs, D3, D300 and D700.
- Solmeta offers offers complete hot shoe GPS solutions for D2H/Hs, D200, D2HS and D2X/Xs, D3, D300 and D700.
- An electronical compass enhances some Solmeta GPS units to write the heading (direction of sight) to the EXIF of the picture. The compass function works with D3, D300, D700. And with D2H/Hs, D2X/Xs after updating the firmware.
- Comparison Solmeta and Dawntech, German
- The 500SE is ruggedised (IP67) and Bluetooth-capable. It will connect to most Bluetooth GPS receivers. Ricoh also sell the rather expensive SE-1 and SE-3 GPS receiver modules that securely attach to the side of the camera. The modules are the same except the SE-3 module includes a digital compass. The 500SE can also store a proprietary format track log. See Ricoh 500SE GPS Log.
- E and N series cameraphones can also geotag photos using the free Location Tagger software from Nokia Beta Labs if they have an internal GPS or are connected to an external unit.
- Jobo has a product called photoGPS that you can put in any camera with a hotshoe. More information can be found on this website: Photo GPS.
- The CL65 is a compact point-and-shoot with 12.2MP and has a built-in GPS for geotagging photos. Bluetooth and Wifi too. Micro SD.
- The WB650 is 12MP, 15x zoom, SD/SDHC.
- The ST1000 is 12.4MP, 5x zoom, microSD, Wifi, Bluetooth.
- Cyber-Shot DSC-HX5V. 10.2MP, 10x zoom, SD/SDHC/MS.
- TZ10/ZS7. 12MP, 12x zoom, SD/SDHC.
- Some BlackBerry devices, such as the 8900, automatically geotag photos using the inbuilt GPS if the appropriate option is enabled in the camera settings.
flickr can be forced to read existing geotag information (Latitude and Longitude flags) in the EXIF header if this option is selected before the images are uploaded. You do this from this link if it's not already set for your account. Once set, all images uploaded that already have their location in the EXIF will use this information to show the images on the flickr map. Unfortunately the Yahoo mapping used in Flickr until November 2006 was not detailed enough really to be able to see the accuracy of individual image placement. This means that many images have already been geocoded against a very coarse map.
See also this article http://www.nytimes.com/2006/11/02/technology/02basics.html
Unfortunately the form of the additional EXIF information is not strictly standardised.
OS X users should note that currently (August 2010), photos tagged in iPhoto or resaved from Preview have their coordinates rounded to 0.01'. This can introduce location error greater than the uncertainty from a GPS unit.
- "Apple iPhoto rounds GPS coordinates to nearest second". 2010-08-02. http://njgeo.org/2010/05/29/apple-iphoto-rounds-gps-coordinates-to-nearest-second/. Retrieved 2010-08-02.
- "More on iPhoto GPS weirdness « Numpty's Progress". 2010-08-02. http://glaikit.org/2010/07/10/more-on-iphoto-gps-weirdness/. Retrieved 2010-08-02.