For the sake of this post we are going to focus on the mobile aspect of the term with an emphasis on Android devices comparing applications that handle geotagging a little differently between each other. First of all, let's answer the question what is a Geotagged photo?
"A geotagged photograph is a photograph which is associated with a geographical location by geotagging. Usually this is done by assigning at least a latitude and longitude to the image, and optionally altitude, compass bearing and other fields may also be included."
("Geotagged Photograph", 2014)
Before we get into applications that can take advantage of a Geotagged photos let's start by how to take one. At the very least you need your GPS turned on and some camera applications require you to go into the options and give the application permission to tag the location to your image as you take it so you will want to check this before you get started. I'm currently using a Nexus 5 and the location option for my photos is turned on at default. This means every time I take a picture a location is attached in the metadata of the image file itself; keep note as that fact is important later. However, with my Nexus 5 and other smartphones this fact varies as if I don't have the GPS turned on it will associate a best guess of where I might be which may default to the Cell Tower location itself, best guess based off cell tower triangulation, or if I have WiFi on the location of the router. If none of the above are available no location information will be tagged to the photo.
So if our goals was to just take a Geotagged photo then we are done right? Sure, but what's the value of tagging the location to images and what do we do with the photo from here?
Attaching location to information has numerous uses but for the common user adding this information is another useful way of helping you search for these images or organize them later. For instance many organize photos by date, event, or people around when the photo is taken. Location gives user the option to find photos based on a map, which in many cases, this is much more efficient in exploring the past rather than finding one particular photo through albums of thousands of photographs. By adding a temporal feature to the map a user can then explore photos taken through time even as events or overlaid at the same spot. This takes us into applications that can help you take advantage of the location data on your photos as each may offer you a different experience depending on what you would like to do.
With Instagram there are two ways to add a photo. One is to upload a photo directly from your phone and the other is to use the application itself to take a photo. Both options will eventually ask me if I want to add a location to my Instagram post and I believe this is more for privacy than anything else. Now this is what is unique about Instagram. Although it will read the location info on your photo to get an idea of where you took it Instagram is actually using that data to be attached to alongside your photo putting the geo data in the Post metadata not the online version of your image meaning once you upload your photo to Instagram the geo data is stripped.
Facebook, Foursquare, and Twitter are the same in regards to how they use Geo metadata. Initially they may take advantage of the information embedded in the image to add to the Post metadata but once uploaded to those applications the images are remade and the geo-data itself is stripped. For Facebook you can edit and change the location of an the image which has the benefit to adding location to images to which didn't originally have this information however the app doesn't actually embed that within the image itself just alongside it.
Why does this matter? One simple word, "Reusable". Well let's say you are using one of these applications as a primary storage for all of your images. You may want to download and reuse the images in something else or perhaps you may someday want to transfer your images to a new storage location. The fact that applications such as Facebook strip the original metadata hurts you as you are then missing information about those photos that make it special.
Should I still use Facebook and Foursquare for photos? For storing photos, No. Use of these applications is practically unavoidable though as everyone uses them for other purposes such as communication and sharing experiences with friends and family. There's nothing wrong with sharing photos to these apps but I would recommend storing your original geotagged photos elsewhere. Another reason is in addition to some of your metadata being stripped the images themselves are reconverted into a lower quality image for online efficiency for those applications. Users sometimes have the option to retain and store the full resolution image but that's a feature that may not be turned on default, just something to be aware of if you care about your photos beyond just sharing them.
Geotagged Data in image Google+ and Flikr are among the best mainstream photo storing applications. Both maintain the original metadata to include geographic location even after editing in those applications. Google+ is known more as a social tool but when you make a post and attach one your photos it retains the Geo-data and allows the user to attach a location to the post separately. This means when you view a post on Google+ from someone who posts from their mobile device you can potentially see where they made the post and when you click the image you can still see all the original image metadata. When you download your images from either Flikr and Google+ you retain everything. Google+ and Flikr just like Facebook also allow you to add location to photos that didn't originally have that info, but once again, the unique difference is these applications actually add the geodata to the image metadata itself which makes these two optimal online storage locations for your photos. These applications provide data transparency allowing you to view the metadata of the images, resusable, and flexibility to let you use them however you want. Flikr even has a feature where you can view all of the publicly viewable Geotagged photos in a map, https://www.flickr.com/map
Another great application worth an honorable mention is Panoramio. There used to be a mobile plugin downladoable from the Google Play store to allow you to upload geotagged images straight to Panoramio but these days its only accessible via desktop. Panoramio only takes Geotagged photos however it does let you edit the photos location after upload. In addition everyone's photos on Panoramio are publicly viewable and searchable on the map as seen to the left. I don't use Panoramio to store my images but instead to share my best geotagged photos.
Why should knowing how geotagging works important to developers?
Knowing how applications use geotagged information is vital to accuracy of the data itself and defining what the data says about the users or their content. Is the geographic location related to the post? Is it related to where the user posted about the event, where the user took the photo itself, both? If I'm looking for geospatial data on my users where do I find it? Am I looking at the images or should I look at something else. Google+ for example may contain multiple layers information that can be use in defining activity on a map. For example when creating an event that event may have a location attached, each post may have a location, and each image. Think of it has defining regional location all the way down to specific location telling a story as time goes on. As a developer this may help you define what activity you want to associate with users depending on where they are so identifying accuracy of geodata is important.
Please let us know in the comments what you think.
There are many more applications out there that take advantage of geotagged photos, this is just a few to help us define the topic. What is your favorite image storage application and why? Do you care about image location?
1. Geotagged Photograph. (2014). Retrieved from http://en.wikipedia.org/wiki/Geotagged_photograph