A pin identifies the location where you have taken any pictures that have been tagged with the geographic information about where they were taken. When you hoover your cursor over a pin, a label appears with the name of the place. If you click on the arrowhead to the right of the label, all of the tagged pictures taken at that location appear in the main window. You get back to the map by clicking the "Map" button in the upper left corner of that window.
You can focus on a particular part of the world by clicking on the drop-down lists that appear in the upper left corner of the map window. The drop-down that appears lists alphabetically all of the countries, states, cities, and places that you have identified when tagging your pictures.
When you focus on a location, such as a country, the number of pins displayed can increase because locations can be identified in more detail. If you were to select a country in which you only visited one city, the map will automatically zoom in to that city and display all the places in the city where you took a picture that has been tagged.
So How Do Your Pictures Get Tagged?
Pictures taken with your portable Apple device such as an iPhone, iPad, or iPod Touch, that have Location Services turned on, are automatically tagged with the GPS coordinates when the picture is taken. Many new cameras have GPS built in. It is also possible to get SSD memory cards for cameras that have GPS built-in so photos are automatically tagged when they are saved to the card.
If you don't have that capability, or if you accidentally had Location Services turned off on your Apple device, or your camera, for whatever reason, was not able to communicate with a GPS satellite when your picture was taken, you may have to tag your photos with the GPS information manually. To do this you make use of Google Maps.
Create a Bookmarklet For Your Browser
The first thing you should do is create a bookmarklet which you will use when identifying a location in Google Maps.
Make sure you have saved this bookmark and that it appears with the name you gave it along with your other favorite bookmarks above the main browser window.
In iPhoto, select the picture you want to tag. Then click on the "Info" button along the bottom right of the iPhoto window. One of the items that appears at the bottom of the Info panel is a map. If the picture hasn't been tagged with a location, the map is a grey map of the world with a field above the map in which appear the words, "Assign a Place . . ."
You can just type in that field the name of the place where the picture was taken. If you have other pictures with that name assigned, the name will appear at the top of a list from which you can select. Otherwise, a Google search for the place is performed. If the place you are looking for appears on the list that is displayed, you can simply select it. A map will be displayed with a pin suggesting a location where the picture was taken.
If you hoover your cursor over the map, a plus and minus sign will appear at the bottom which you can click to zoom in or out of the map. Also you are able to choose "Terrain", Satellite" or "Hybrid" for the type of map you want to display. There is also an icon to the right of the plus and minus signs, which when clicked, will cause the pin on the map to be centered in the window.
You may find that by zooming in, and moving the map around, you are able to locate where you were when the picture was taken. You can move the pin to the location on the map by grabbing the pin by clicking on the pin, holding the mouse button down until the cursor turns into a clenched hand, and dragging the pin to the location.
When performing the Google search for the location, if you type in an address for the name of a prominent structure such as the Eiffel Tower or Mount Rushmore, the pin will land on the structure. You may be satisfied with identifying the location of the picture to be that landmark. However, when taking a picture with a camera with GPS or an Apple devise, the location tagged is the location of the camera, not the location of the subject of the picture. For consistency and accuracy, the location of the camera is the location I prefer to use when tagging my pictures.
Again, you may be satisfied with simply moving the pin on the map in iPhoto to the approximate location where you were standing when you took the picture.
However, if, for example, you are doing genealogy research and are taking pictures of markers in a graveyard, exact location is very important. With GPS these days, accuracy can be within a few feet, depending on conditions.
This is where our bookmarklet comes into play.
Using the Bookmarklet
The first thing to do is to bring up your browser and, using Google Maps, find the location where you were when you took the picture. Take advantage of Street View and the photos that have been uploaded to Google Maps to determine that location with as much accuracy as you desire.
Once you have identified the location, with the cursor pointing to that location, right-click or control-click your mouse. A contextual menu will appear, and one of the items on the menu is "Center Map Here". Select that item. You will see the map shift so the location you are interested in is centered in the browser window.
Now click on the bookmarklet you created above the browser window. A small window will appear which contains the GPS coordinates of the location in the center of the map.
Copy those coordinates. Go over to iPhoto and paste them in the "Assign a Place . . ." field above the map in the Info panel. iPhoto will place a pin on the map at those coordinates.
You can leave the GPS coordinates as the name of the place if you wish. Otherwise, you can type over the GPS coordinates with a place name of your choice. You will then be able to use this same place name for all other photos you took at that location.
It takes time and some work to get your photos geo-tagged. I am happy that I was able to take the time to make the effort. It is rewarding to be able to choose a location on the map in iPhoto and see all the photos you took when you were there.