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PhotoLinker 2.0 ($US50, 30 day trial) is described by its developer as a 'pro geotagging and annotation tool'. Geotaggers who were familiar with GPSPhotoLinker will recognize the family resemblance, but will also appreciate the magnitude of changes this new app brings. It's no longer dependent upon use of a GPS track logger for a start, as integrated mapping now supports a manual geotagging mode (hence the dropping of 'GPS' from the name). There are improvements to workflow, a map viewer, a facility for track and waypoint management, and the pièce de résistance—EXIF metadata annotation. And yet it retains the incredible flexibility and the same precise control over automatic geotagging parameters that I appreciated in my review of GPSPhotoLonker. This post takes you on a visual walkthrough of the many new and refined features.

Disclosure: A single user license for PhotoLinker was provided by Early Innovations for the purposes of this evaluation (v2.0.1). I have a personal interest in the success of the Geotag Icon.

Offset

When you first click on the Geotagging Console button a HUD prompts you for the time zone your camera was using when the photographs to be geotagged were taken. As a general rule this is easier if your camera is always set to UTC (GMT) which is what your track logger will also be recording. The HUD helpfully prompts you to use a date and time-shifting tool if the images and tracks you load don't appear to match.

Adding tracks and photos

You can add GPX tracks, single or multiple, by dragging a file selection onto the uncluttered PhotoLinker window—including files in folders. The Track & Waypoint Browser window will automatically open, showing the import progress (for more on the features offered within this window see below). Photos can likewise be dragged individually, as a selection, or within a folder onto the PhotoLinker interface.

Alternatively, PhotoLinker uses GPSBabel to download data directly from a range of GPS receivers. To access this option see the Tracks > Download From GPS menu.

Automatic geotagging mode

If you select a photo or photos, the proposed geolocation for each will be shown on the map by a purple funnel-shaped placemark. This provides a quick and easy visual indication that you have correctly accounted for any offset and that automatic geotagging can begin. In addition to being able to zoom in on a given placemark you can also mouseover it to reveal the proposed metadata that will be associated with it.

If things aren't looking as they should at this stage you can revisit the offset HUD as above by clicking the Camera Settings button. Now might also be a good time to review the parameters that will be applied during automatic geotagging, by clicking the Edit Criteria button.

By tightening up on the criteria here you can ensure that only the most accurate track points are time and/or distance-matched to your images, effectively forcing a manual review of the more dubious proposed matches.

With your images selected automatic geotagging becomes a one-click operation: just click on the Geotag n Photos button in the Console. Geotagged photos will be displayed with a red pin instead of the purple funnel. Pins and images are linked, so clicking on one will highlight the other.

Your images won't actually be geotagged until you click the Write Changed Tags button in the top left corner of the PhotoLinker window. You have full control of how saving is handled too: be sure to look over the save options in Preferences > Photos.

Manual geotagging mode

If you haven't recorded an automatic track log using a GPS device, or if you temporarily lost reception whilst recording one (e.g. inside a building), manual geotagging allows you to attach location data to images that cannot be geotagged in automatic mode.

Simply centre the map beneath cross hair to 'target' the currently selected image. The cross hair can be rather hard to see (as in the example below) depending upon the map background, although becomes more visible when you use the hand tool to move the map. As you do so the coordinates of the map centre will update, and can be applied to your image with a click. Note that you can select multiple images and batch-apply the current coordinates to all.

The other type of manual geotagging you may wish to perform is attachment of GPS waypoints to an image or images (for an explanation of the difference between track points and waypoints, see here). Waypoints can be downloaded in GPX format from some track loggers (operating in manual mode), personal navigation devices, and software such as Google Earth or RouteBuddy. Clicking the Show All Waypoints button brings up the Track & Waypoint Browser window: select the waypoint you want to associate with your image(s).

Single geotagging mode

This mode lets you step through your images and decide, on a case-by-cases basis, whether to geotag using the preceding, next, or time-weighted average track point. If you were to zoom right in on the map a high degree of precision allows you to be be very particular about the assigned location; this could be especially useful when there is a greater than expected interval between track points, and you're not sure which point is the more accurate, for example.

Integrated workflow

If using Auto mode you may find that a proportion of your images could not be geotagged. At this point you have the option to relax the geotagging parameters (via the Edit Criteria button), but personally I prefer to keep these strict and review individual images that 'fail' to acquire coordinates.

PhotoLinker can help in providing a smooth workflow for doing this: switch the view in the photo panel from preview to list, at which point images that have no associated coordinates become readily identifiable. Activate the toggle to display the photo thumbnail viewer to provide an extra visual reference to the selected image. Now swap over to Single mode and select the most appropriate track point by referring to the map (or Manual mode if there are no appropriate nearby track points).

Click thumbnail to enlarge image

Case-by-case review of images failing auto criteria

If you view the larger image above you'll notice the checkbox labelled Auto advance. This will advance to the next image in the list—not the next image without associated location data. I'd like to see a user preference here to auto advance to either the next image (when working solely in Single mode) or to the next non-geotagged image (for review of failures after an automated geotagging session).

Reverse geocoding

Reverse geocoding is the process of acquiring address information from a coordinate pair. This requires online access to a server, the choice of which you can specify in Preferences > Photos.

If you have images that have been geotagged while offline using a track log then it is possible to subsequently re-import them into PhotoLinker and perform reverse geotagging when Internet access is available. However, PhotoLinker will recognize these image(s) as already geotagged and will not merely append city/ state/ country etc. to your existing geodata. Instead you will need to chose Remove GPS Tags from the Photo menu to permit re-tagging. As a destructive process the obvious disadvantage here is that you will loose any precision location of photos that could not be geolocated automatically according to your preferred criteria. For example, in the illustration below an image had been precision-geotagged while offline using a waypoint (left). Once online again PhotoLinker was used to automatically geotag the same image after removal of existing metadata (right); notice that the human-readible location data have been added but the coordinates have changed since the original ascertainment has been destroyed:

For images that already have saved coordinates I would like to see an 'update' option that performs reverse geocoding only.

Map viewer

As you will have noticed from the above illustrations PhotoLinker supports access to a variety of online maps. One map notably absent is Google Maps and this is not without good reason. It's not just Google, however, as Microsoft and Yahoo! likewise deny developers access to the same map tiles that end users can directly access for free anyway. Despite such restrictive terms of service many a developer has seemingly chosen to ignore them and include access to these maps in their paid-for applications. PhotoLinker's developer has come down on the side of caution, preferring to stick with a safer long-term business model despite the small compromise this entails for would-be application purchasers.

Unfortunately the selection of currently available mapping does not include high resolution satellite views outside of the United States, which are particularly helpful for manually locating images by reference to photographic features. The loss of Google Maps is most noticeable here and the upshot is that PhotoLinker is best suited to automatic geotagging if you live outside of the US (HoudahGeo retains a Google Maps satellite view for those who are faced with blank map tiles; review here).

Track and waypoint management

Whilst not a well-developed track management application (see RouteBuddy or TrailRunner) PhotoLinker does provide a very reasonable track management feature. By comparison HoudahGeo's new track log inspector is considerably more rudimentary.

You can browse your imported library by filename or by date, and selecting a track or waypoint and then clicking the zoom tool in upper right of window will auto-fit the map display to those data. The browser offers the option to customize the name or display of the track (colour, point size)—much as you do when using Google Earth to make custom KML/KMZ files.

EXIF metadata annotation

It's worth watching the introductory screencast to see this feature in action; this is where PhotoLinker excels. Select the individual photo you wish to annotate. For example, you might add keywords on a photo-by-photo basis. Alternatively a multiple selection will apply the annotation to all selected photos (batch mode).

The Customize button brings up a list of alternative tags. Just drag-and-drop grouped or individual tags to the left pane. If you plan to do this often you'll surely avail yourself of the option to save custom tag templates.

Click thumbnail to enlarge image

The awesome PhotoLinker metadata editor

Predefined tag sets comprise the following:

• Name & Date
• Common Tags
• Geotags
• Camera
• Location Created
• Photo Description
• Digitization Attributes
• Location Shown
• Photographer
• Photographer Contact Info
• Document
• Newscodes
• Rights
• GPS
• Organization

PhotoLinker isn't going to force you into using a predefined set, however, as you can drag-and-drop editable fields to and from any existing set to produce a truly custom annotation view to suit your personal workflow. Fantastic.

Don't worry about remembering to click the Write Changed Tags button to save your annotations; PhotoLinker will automatically and helpfully prompt you to do so if there are unsaved changes.

Sharing, photo organizing, and data retrieval

These aspects of workflow are not part of the PhotoLinker feature set. In this respect HoudahGeo is the better choice if you desire an 'all-in-one' application for sharing your geodata to Flickr, Locr, or to Google Earth. As for organizing your images by location most people won't do better than the new Places feature introduced with iPhoto 09. It would be remiss of me not to mention the powerful metadata searchmeister, CDFinder, in relation to data retrieval (review here with update)—the perfect companion for PhotoLinker annotators wanting to get out as much data as they put in!