Computational photography, location services
July 17, 2021
Whether you use a traditional digital camera or the camera app on your smartphone, it takes two steps to take a digital picture: the physical step of capturing an image and the image processing step.
Digital cameras have bigger sensors and better lenses and take better initial images, while smartphones, with their smaller sensors and slower lenses, have better software for manipulating images. Image manipulation software uses computational techniques to enhance photos, which leads to the term computational photography (CP).
Of the available CP techniques, stacking is the most common. The camera takes multiple photos at slightly different times and focal lengths and then "stacks" them together to make what the software thinks is the best photo. Stacking is also the technology behind any High Dynamic Range (HDR) photos you take.
If your smartphone has a big enough camera sensor, it might use a CP technique called "pixel binning." Instead of stacking photos to get a good one, pixel binning takes the best pixels of the images and combines them into a very high-resolution image.
Night mode is a CP technique that uses HDR to shoot multiple images at different exposure lengths and then combines them to get the most detail.
Portrait mode is a CP technique that analyzes an image and blurs the background of the objects furthest away from the lens.
Wait, how does the software "know" which image is the best? Neural networks.
A neural network is a bunch of algorithms that process data, in this case, the data in digital images. The algorithms mimic the process human brains go through when picking out an excellent picture.
Location services is a generic term for how your device "knows" where you are. For example, your location is vital if you're in Boston and need to find an excellent Italian restaurant. But how does your phone, laptop or tablet figure it out?
Location services can use three ways to figure out where you are: GPS, cell towers and Wi-Fi.
If your phone has a GPS chip inside, and most do, location services ask the GPS radio to find your location. But most laptops and quite a few tablets don't have a GPS chip, so how do location services work in those devices? That's where cell towers and Wi-Fi come in.
If the GPS signal is poor in your location, or your phone doesn't have a GPS radio, your phone or cell-enabled tablet can use nearby cell towers to figure out where you are. Maybe not the exact address of your hotel in Boston, but at least that you're not in Tehachapi anymore.
If your device doesn't have either a usable GPS or cellular signal or doesn't offer either of those options, your device (we're mostly talking laptops here) likely will use Wi-Fi to find your location. So, think of it as a Wi-Fi positioning system.
Location services on your laptop looks around and builds a list of the available Wi-Fi networks and the signal strength of each network around your location. Now, using the Wi-Fi you're connected to, your laptop connects to servers that contain lists of Wi-Fi access points around the world, compares the signal strengths of the surrounding connections and figures out where you are. This method can be even more precise than GPS in densely populated areas.
But who made the Wi-Fi lists and doesn't that information change all the time?
Initially, the Google Street View cars scooped up Wi-Fi info as they drove around mapping the world. But now every phone, laptop and tablet is constantly scanning for Wi-Fi signal information and updating those databases.
But what about privacy? Any Wi-Fi access point's name, IP address and unique MAC address is public information. The router broadcasts this information so devices can find and connect to the network. The routers don't reveal passwords, lists of connected users or physical addresses, so none of that information ends up in the databases.
All modern operating systems prevent apps and websites from using the Wi-Fi positioning system unless you permit them to do so. That's what those annoying messages are that ask to use your location are all about.
Do you have a computer or technology question? Greg Cunningham has been providing Tehachapi with on-site PC and network services since 2007. Email Greg at email@example.com.