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    Smartphone navigation
    From: Frank Reed
    Date: 2012 Jul 20, 13:39 -0700

    Modern "smartphones" are pocket computers. They can do amazing things even without being activated as a phone. For example, I have an "old" first-generation iPhone from late 2007. It has no phone service, but it is fully WiFi capable so I have it as a spare Internet access device. If I am upstairs and my phone (a two-year-old Android Smarthpone) and laptop are downstairs, and my upstairs computer is off, no problem. I pick up the old iPhone, and I can almost instantly view any web site, check email, check NavList messages, and so on. I can also launch spreadsheets and run various astronomy programs that can do nearly anything that I would expect to see in a "desktop" computer astronomy application. Solve a spherical triangle correctly in all angular ranges? Hell, they do that in hardware --it's on the GPS chipset!

    Modern smartphones are more than pocket computers because they also include a "rich" suite of sensors. And that's an understatement.

    Smartphones can listen. If you've never seen "Shazam" in operation, it will seem like magic. A song is playing on the radio... you decide you want to follow the lyrics... so you tap an icon on your smartphone, tap another icon to set it "listening" and in five or ten second it comes back with the name of the song, the artist, the album artwork, a link to the lyrics, and more. And for many songs, if you tap another button, it will go into a "karaoke" mode and display the lyrics synched to the song still playing on the radio. This isn't science fiction. I do it almost every day.

    Smartphones can see. And I don't mean that they're cameras. They are indeed cameras, and smartphones have nearly wiped out the pocket camera market. But it goes beyond that. They can analyze what they "see". This functionality is relatively limited, but if you start up an app, for example, "Google Goggles" on your phone and point the phone at a piece of artwork (maybe a Renaissance painting in an advertisement in a magazine), or the cover of an old paperback book, or a logo on a bottle of wine, the app will analyze the image and then compare it with Google's vast database of images and often locate an exact match. In the case of the painting in the advertisement, it will then most likely link you to the Wikipedia article for the artist who painted it. And of course, this functionality can include translation: photograph a street sign in, say, Portuguese, and your phone will translate it for you. This basic "vision" functionality has been available for several years now. Big improvements are in the pipeline.

    Smartphones can measure altitudes and find directions. The earliest smartphones included accelerometers in two dimensions that could determine the tilt of the phone in two directions. This has obvious applications for leveling applications and basic celestial navigation. But bear in mind that the accuracy is no better than a tenth of a degree AND the device has to be calibrated since the accelerometers are aligned with the frame of the smartphone only to within a degree or two (in other words, there is an index correction, unless it is calibrated manually, of more than a degree in most cases). Nonetheless, this has made angular altitude measurement with Smartphones a relatively trivial application for nearly five years now. Back in the Spring of 2009 rumors began circulating that new smartphones would also have electronic compasses, and at that point, as I am sure some of you recall, I posted on NavList about how this could turn any smartphone into a star finder (and there was much "grumbling" on NavList about the impossibility of this). Less than a month later, Google Sky Map (now known simply as Sky Map since they have made it open source) became available and now there are numerous "point and shoot" apps for star-finding on smartphones (e.g. "Pocket Universe" on iPhones). It's important to recognize that these are only as good as the calibration of the compass. Since many smartphone users do not know that they have to wave the device around in a peculiar fashion to calibrate the magnetic compass (and since those who know, often feel embarrassed doing it), the direction capability is sometimes wrong by 10 or 20 or even 45 degrees. When calibrated, the error is typically less than five degrees. For over a year now, many smartphones have also been equipped with an electronic gyroscope. This can separate changes in orientation from linear accelerations, which is very useful in games but also in star-finding apps since it tends to smooth out the turns. I cannot emphasize enough that star-finding apps like this are tremendous crowd-pleasers. They are a fantastic way to learn the stars, both for beginners and experts. For myself, I enjoy placing the device on a table with Sky Map running. It lets me "look through the Earth" and see what stars are in the nadir at that time, something that we are rarely aware of even when we know the night sky well.

    Smartphones can determine your position. Long before iPhones and Android phones, smartphones have had GPS chipsets and other more coarse means of determining the user's position. There are now multiple methods of position-determination. GPS positions provide a fix within just a few seconds. There's no long bootup wait like in old GPS receivers since the network now provides the startup data to the device based on its coarse position which is found from Internet "IP" address or from the location of the nearest cell tower. In addition, huge databases have been created, originally by small startups but they have all been eclipsed by the Google beast, which provide the physical locations of millions of home WiFi networks. Those trucks that compile photography for Google Streetview are also sniffing the id's and signal strengths from the WiFi in you home and business. This WiFi-based positioning is nearly as accurate as GPS and it works especially well in those "urban canyons" where GPS is not quite so reliable. And note that even a coarse position based on network location is more than enough for star-finding and most astronomy applications.

    Smartphones create augmented reality. By combining multiple sensors and especially the device's camera, it is possible to display data directly on the camera's live view of a scene. You aim your phone down a street and it labels every restaurant, for example, and shows yelp ratings in little bubbles floating over each one. This sort of application has been slow to catch on in large part because of the embarrassment factor of aiming your phone down a street.

    Smartphones are watching you. Among the most recent enhancements are phones that watch your eyes and know whether you're reading the screen. If you're still reading, the display will not "time out" and go dark. Strange but true. Disturbing yet practical. And smartphones are already doing facial recognition but strictly on an "opt in" basis because of privacy concerns. In other words, the technology can identify specific individuals and note their presence in photo after photo but you have to tell the phone that this person is "Jane Doe" from your contacts list.

    A short note on naming: there are at this time two dominant operating systems on smartphones and related tablet computers. They are iOS and Android. Apple created and developed the iPhone, first launched in 2007 and they have since named its operating system "iOS" to cover the multiple devices it runs on, especially the sizzling hot iPad. Google almost simultaneously launched the Android operating system to steal as much as they could from Apple's projects without going to jail. There is a good analogy here with the Mac versus Windows in the 80s and 90s. Since Apple has not licensed iOS and probably never will, the market of devices which run iOS is quite small but beautifully integrated and efficient. It's "iPhones" and "iPads" with the "iPod Touch" as a minor shrub in the Apple orchard. From the outset, Google has attempted to make friends and influence corporate partners by selling Android as the "open" alternative to Apple's walled orchard. This has also partially protected Google from massive lawsuits since Apple has gone after the device manufacturers who use the Android operating system first. This approach has led to a proliferation of devices and serious fragmentation of the market (since there are numerous major versions and minor variants of Android). In addition, all of these devices have unique names despite the fact that they are all running Android. So for example there are Heros, and Nexuses, and Galaxies, and even the Nook and the latest Kindle tablets run Android. There is also a line of phones from Motorola called Droids. This is where things can get confusing. All Droids run Android, but by no means all Android devices are Droids. For people who are familiar with the Apple side of the market, this is especially surprising. Incidentally, the name "Android" required no special licensing since it is a long-standing generic science fiction term. But Motorola had to license the name "Droid" from a very wealthy man. Can you guess who? Hint: "These aren't the droids we're looking for."

    Finally, as far as Gary's report of less than 5 minutes of arc error in an LOP from a smartphone app, that's either good luck or it's an app that is cheating (perhaps even in a way that the programmer did not realize). There's no magic here --beyond the amazing magic that you get all of these features in a handheld device... oh, and it's a phone, too... :). The device cannot be better than an ordinary bubble sextant as far as altitude measurements go. Without calibration for index error, you can expect errors in LOPs of one or two degrees. With calibration and assuming no magnification and sighting along the edge of the device, you could expect no better than about half a degree accuracy on a single sight. This could be improved exactly the way that traditional bubble sextants improved accuracy by averaging over time. And of course, this would be an easy addition to a smartphone app. If there's calibration for index correction, and if averaging is done, and if there's a nice clean edge to sight along (no guarantee given the multitude of Android devices), I think you could expect standard deviation errors in sights on the order of five to ten minutes of arc. Of course, if we throw in coarse positioning from a user-input DR or from the network, the device could also usually guess what stars you're looking at and you wouldn't even need to know basic star patterns to get a position. Useful? Probably not in any real practical sense. Fun? Well, for a certain personality type. Myself included. :) Educational? Absolutely, if you ask students to figure out what the device is doing and relate it back to historical navigation, there's a thousand lessons here. And that's really the great thing about all of this: any "kid" with a smartphone, ignoring obvious financial barriers for the moment, can download these software apps and learn star-finding and navigation topics and a thousand other things... There's tremendous opportunity for education.

    -FER


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