Automatic geocoding use a track log from a GPS device or iPhone app
Incremental geocoding places photos along the path you traveled
Location information will allow Apple Photos to show your images on a map. It will help you look up images that you did not otherwise file or tag.
Knowing – and showing – where you took a photo adds to its “story”. On the map in Photos and Photos Workbench you get a bird’s-eye view of where you took your photos and the route you took to get there.
Automatic geocoding in HoudahGeo matches photos to a GPS track log. A track log is a record of where you have been. A GPS app or track logger records your current position and the current time. It does so every few seconds and thus creates a breadcrumb trail of your travels.
HoudahGeo figures out where you took a photo by matching the timestamp on the photo with the times in the GPS track log. While the GPS device gets accurate time information from satellites, your camera clock is probably not accurate. Most cameras also do not record time zone information: the photo coming out of the camera may say it was taken at 12 PM, but there is no telling if that is to be understood as 12 PM east coast or west coast – a 3-hour difference.
Timestamps in HoudahGeo
HoudahGeo needs to know the exact time a photo was taken. That is why HoudahGeo asks about camera clock settings when you import images.
There are 4 ways you can tell HoudahGeo about your camera clock settings. The first 3 are found in the Load > Camera Setup… panel. This panel pops up automatically when you import photos that lack time zone information.
Geocoding using GPS data is arguably the quickest method of adding location information to photos. The GPS data comes in the form of a tracklog file recorded by a GPS device or smartphone app. Every few seconds a record of the current time and location is added to the tracklog.
Besides location coordinates, the GPS device can record additional information like altitude, heading, or speed. When HoudahGeo matches photos to the tracklog it can copy both location coordinates and such additional information to photo metadata.
At the same time, some cameras have sensors that can provide such additional information even when not using a GPS receiver to add location coordinates to a photo.
A compass built into the camera body can, for example, provide viewing direction information. This would be more accurate than a view direction computed from the direction of travel between to locations recorded in the tracklog.
When the same information is available from two sources – the GPS tracklog and photo metadata – you are left with the choice of which to trust.
Some GPS cameras use a barometer to determine the current altitude. These cameras can write altitude information to photos even when the GPS feature is switched off. This is often seen in Panasonic cameras.
The camera creates photos that have altitude information, but lack latitude and longitude coordinates. This comes as a bit of a surprise to HoudahGeo and requires a few additional clicks on your part.
We’ve been dreaming about trekking to the top of Mount Kilimanjaro for quite some time. Last October, we finally made the trip. Climbing Africa’s highest mountain, crossing its different climatic zones and finally reaching the summit was an amazing once-in-a-lifetime experience. We documented this unique vacation by taking hundreds of photos – and by recording a track log.
In part 1 of this blog post series, we discussed how you can use reference photos to speed up your geocoding process. The easiest, fastest and most precise way to geotag your photos, however, is to provide HoudahGeo with a so called track log file. While there are smartphone apps which record track logs (as discussed in part 2), these may drain your phone’s battery if left running over a prolonged period of time. Therefore, you may want to consider investing in a GPS track logger.