How to add a location to photos in the new photos app?

In OS X 10.10's Photos application, location information is read-only.

Photos reads GPS coordinates from image files during import and displays the location in the Info window. It can also show photos belonging to a collection or moment on a map. The "Photos Help" puts it this way: "If your camera has GPS capability (as iPhone does), or you’ve added GPS information to your photos, Photos can automatically display your photos on a map."

Unfortunately location information is also read-only by the way of Apple Script. I develop the photo geocoding software HoudahGeo. When used with iPhoto or Aperture, this allows for a very elegant workflow:

1. Import photos into iPhoto or Aperture
2. Geocode the photos using HoudahGeo or other free software.
3. Write geotags to the original image files
4. Have HoudahGeo notify iPhoto or Aperture of the newly added geotags

The last step of the workflow uses Apple Script to update the library to reflect the location information added to the files. This is not currently possible with the new Photos application.

Until Apple adds the option to change location information via Apple Script, we have to resort to a less elegant workflow.

1. Import photos using the Image Capture application
2. Geocode the photos using third party software like HoudahGeo or other free software.
3. Write EXIF/XMP geotags to the image files
4. Import the tagged files into your Photos library

This workflow does have its advantages. The process of updating the iPhoto or Aperture library for thousands of photos can be rather slow. Adding the GPS information before import is faster.

The above workflow also ensures that GPS information is stored as EXIF/XMP tags within the image files. Just the same as if you had used a GPS camera. The location information will thus always stay with the images.

Update for macOS Sierra:

With Apple Photos 2.0 and HoudahGeo 5.1 running on Sierra it again possible to notify Photos of changes made to location information. I.e. HoudahGeo will geotag orginal image files with EXIF/XMP tags and then pass on location information to the Photos app.

It appears that this has changed as of Photos 1.1 (El Capitan).

According to this article, adding and editing geolocation data is a new feature.

Photos 1.1 addressed this major customer pain point with the introduction of an Assign a Location feature available within the Inspector window.

See also the following excerpt from this article:

In Photos 1.1 you can add a location to an image or batch of images that weren’t geotagged, as well as edit the location of data of already-geotagged images. To do this, you open the Inspector window by pressing Command-I. In a not-yet-geotagged image, the Inspector will display a line labeled Assign a Location. Clicking in this area will let you enter a street address or a name of a point of interest, and Photos will search Apple’s Maps database. If that location isn’t good enough for you, you can always click on the pin and drag it around the map, placing it wherever you like.