Photo mapping
From OpenStreetMap
An increasingly popular mapping technique, photo mapping can be a great timesaver - it can be far quicker taking photos of street signs or points of interest than either to write it down or fiddle with the GPS waypointing. What's more, since digital cameras add the date and time to each photo (in the EXIF data), and the GPS tracklog can be used to convert the time into your exact position, it's easy to match up the photos to the exact position they were taken.
To get the positioning right relies on the camera having its clock set accurately, ideally down to the second. However, on many cameras you can only set the time to the nearest minute. To get round this, there's a better way - take a photograph of the GPS' screen while it's displaying a clock, and that can be used to calculate the offset in seconds between the camera and GPS. Alternatively, many cameras automatically set the seconds to zero when the time is set, so you can synchronize the camera and GPS by setting the camera's time just as the GPS rolls over to a new minute.
It can be difficult to determine the way you were facing when taking a photograph. The following trick (due to User:lonvia may help:
One way to solve the orientation problem is to simply rotate the camera: landscape pictures for what's ahead, portrait-size for infos about the way you just came from and a rotation of +/- 45° for what is on the right/left of the road. Pretty low-tech, but sufficient most of the time.
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Integration with JOSM
The best way of working with photos in OSM is using JOSM
First open a GPX file. It should then be listed as a layer (Toggle the 'Layers' panel, if it isn't visible). Right-click the layer listing, and select 'import images'. Select all the images (or the folder) you want. It will overlay little thumbnails on the track based on the time the image is taken.
To adjust for the time offset (you will need a photo of the GPS showing the time), right-click on the new "Geolocated images" layer listing, and select "Sync Time". Select the image required, and then enter the time shown on the image of the GPS. JOSM will then compare that time with the photo's EXIF timestamp, calculate the time offset, apply the offset to all the EXIF timestamps, and move the photos into their corrected positions. JOSM remembers the synching so you should only need to do this once (until next time you fiddle with time settings on either device)
The "Geotagged photos" feature is built in to JOSM. However you might like to try out the AgPifoJ plugin which works in a similar way, but offers enhanced reliability and usability.
Tagging and storage
If you want to tag an object (node, way etc) to show that you positioned it using a photograph and not GPS data (perhaps a fence you didn't walk along running directly between two places already on the map), use "source=photograph". If, more commonly, it's the name of the object that you got from the photo (e.g. a street name), use "source:name=photograph". Similarly, for road numbers (e.g. ref=A305), use "source:ref=photograph".
There's nowhere within the OSM project for the photos themselves to be stored. If you upload them to a website such as flickr, you can use the "source_ref=http://example.com/123.jpg" (or "source_ref:name=" or "source_ref:ref=") tag to link the photo to the object.
If you're using the Annotation Presets with JOSM, it'll suggest the right tag at the right time, and you won't need to worry about which one is which!
- See also: Source for more source-tagging options
Other Software
OJW's image locator script can combine a directory full of JPEG images, with a GPX tracklog, to produce a list of latitude/longitudes for each photo.
Seth Golub's geocoding scripts do pretty much the same thing, but write the data into the EXIF section of the JPEGs using exiv2. The scripts also provide a more usable command line interface to exiv2 for reading and writing geographic data to/from EXIF headers.
More software and informations about writing location in the pictures metada can be found on the Geotagging_Source_Photo wiki page.
Some Nokia camera phones do not include date information in EXIF headers, causing JOSM and other tools to fail. The date and time can be copied from the file creation time using the useful Perl library and command-line application exiftool : $ exiftool -P '-FileModifyDate>DateTimeOriginal' *.jpg
For the Linux users there is GPS Correlate which has command line and GUI apps. Available in most re-po's.
Other projects
- There is a flickr tag for openstreetmap photos.
- Photos can be used for the Geograph project (Use this page to upload with lat/long instead of BNGR)
- Check if there's a Wikipedia article you can illustrate with the photos. Remember: it is best for the Wikimedia projects to upload the file on Wikimedia Commons. There may also be a wikitravel guide you can illustrate with the photos.
Better (sunny weather / picturesque) photos tend to be more welcome (and not just pictures of a street sign!)
