Pondering the progress of technology – comparing my first hand-held GPS receiver from 1999 to the GNSS chip that’s in my 2019 smartphone…
20-ish years ago I acquired a Magellan GPS 315 – purchased from a shop in England’s Lake District – it was primarily going to be a navigation aid for camping/hiking etc. I’ve still got it and it still works. It’s slow: it takes at least 5 minutes to get a lock, it needs a clear view of the whole sky (even slight foliage cover upsets it) and it eats a set of AA batteries in just a few hours. In contrast the smartphone I had in 2019 (Samsung Galaxy S10+) is roughly 20 years younger than the Magellan GPS and also contains a GNSS receiver as well as all the other functions & sensors built-in to the phone. In my job at Chronos I deal with atomic clocks and accurate time/frequency distribution systems, most of which utilise GPS/GNSS receivers as sources of UTC and this lead me to consider what progress has been made in those 20 years from GPS315 to Galaxy S10+?
Thanks to the excellent book “Things Come Apart” by Todd McLellan we can see inside the Magellan without slicing it in to pieces. It basically consists of RF front end (antenna, filters, AGC), some A-to-D and the brains (signal aquisition, tracking, navigation solution) in an ASIC & micro-controller/ROM/RAM with a dedicated LCD display and keypad. My unit has a manufacturing date-code of “13 99” so it was built in 1999. The specifications claim this is a 12-channel receiver – that means it can decode & lock to the signals from at most 12 satellites at the same time. It’s a big chunk of 1990s electronics dedicated to just one task which it does rather well.
I upgraded my previous smartphone to the Galaxy S10+ in 2019 – exactly 20 years after the GPS 315 was built. Thanks to the Tech Insights site we can see inside the Samsung Galaxy S10+ too – amazingly the “GPS” receiver function is now contained in a tiny 3mm x 5mm Broadcom BCM47752KLB1G GNSS chip. It’s also much more fully featured than the GPS315 as it is “multi-constellation” and can receive not only GPS signals but also signals from the GLONASS, GALILEO and BEIDOU constellations. It takes just a few seconds to get a fix and the power consumption is orders of magnitude lower than the old Magellan unit too. The GNSS function is just a tiny portion of the whole Galaxy S10+ device, which by 1990s standards looks like a supercomputer.
move the slider above ⬆️ ⬆️ ⬆️ to see inside GPS 315 and Galaxy S10+
Broadcom BCM47752 GNSS chip in the Galaxy S10+ is multi-constellation and gets a fix in a few seconds – Android GPSTest app shows 35 satellites in view!
|Magellan GPS 315||Broadcom BCM47752|
|150 (1999 price)||3 (estimate)|
|Constellations||GPS||GPS, GALILEO, GLONASS, BEIDOU, QZSS, SBAS|
|Bands||L1||L1, E1, B1, L5, E5a |
|Channels||12||at least 38|
|11 x 5 x 3||0.5 x 0.3 x 0.1|
 Although the Broadcom chip may be dual-band capable, not all Android phones are configured to use both bands. My Galaxy S10+ clearly only showed L1/E1 signals. See https://barbeau.medium.com/dual-frequency-gnss-on-android-devices-152b8826e1c for an in-depth analysis of multi-constellation/mutli-frequency (MCMF) support on Android.
(not to be confused with MCMF – a program I wrote to enable MF4/DTMF dialling in 1995 for an old computer 😉 )
Continue Reading to part 2 to look at specific week number rollover (WNRO) issues with the GPS 315…
Forward to Part 2: https://zedstarr.com/2021/06/15/magellan-gps-315-vs-the-future-part-2/