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Actually this is a very good question for engineers, as the (wrong) idea that a smartphone regularly sends data to a satellite shows fundamental lack of knowled
by littlecranky67 5y ago
Actually this is a very good question for engineers, as the (wrong) idea that a smartphone regularly sends data to a satellite shows fundamental lack of knowledge in some very basic physical understanding. The basic understanding should be: transmitting/sending = emitting energy (costly if a device runs on batteries), receiving/listening for a signal = almost for free nowadays.
I also like the question because even if you have no idea how GPS actually works, you could quickly come up with the rough idea yourself given that you have a bunch of satellites that can emit arbitrary signals. Lots of room to show creative and analytical thinking here.
- wonnage 5y agoI have a hard time imagining engineers in any other field (e.g a structural engineer) would be getting asked questions about GPS as a proxy for general engineering knowhow.
- lazide 5y agoDo you have experience interviewing or seeing interview questions in those fields?
- littlecranky67 5y agoYes, you will be asked to showcase 2-3 side-projects such as houses, bridges and tunnels you built & designed in your backyard and discuss your design decisions on a whiteboard.
- dpark 5y ago> Actually this is a very good question for engineers What kind of engineers are you interviewing? > I also like the question because even if you have no idea how GPS actually works, you could quickly come up with the rough idea yourself given that you have a bunch of satellites that can emit arbitrary signals. I find this really doubtful. Someone who doesn’t already understand how GPS works is unlikely to derive it from first principals in a brief interview.
- littlecranky67 5y agoIf you make some simplifications and assumptions such as a GPS receiver has a highly-precise & synchronized clock (it doesnt), you can conceive GPS basically as a system where each satellite simply broadcasts its position & own current timestamp and then determining your position of the earth surface becomes basic triangulation calculating the time-in-flight of the received signal from multiple satellites. Of course a lot of simplifications in there (such as constant signal expansion time), but I would say a system that you could design with basic geometry. The required knowledge is basic physics and math that everybody calling themselves engineers should have heard at uni (or even at school).
- dpark 5y agoOk, but feeding the candidate half of the information is pretty different from coming up with the rough design with “no idea” how it works. Yes, if you basically tell them how it should work, then they can probably figure out how to calculate the time difference and do some trig.
- littlecranky67 5y agoI mean if the candidate would insist that the smartphone sends a signal to the satellite, you can go on and ask "what kind of data?" -"Nothing, just a PING to which the satellite answers with a PONG that contains its position". This is not at all how GPS works, but this system would also work (in a sense you could determine your position on earth based on the RTT + transmitted satellite coordinate). It is not that the candidate should come up with a perfectly correct solution (actually this could be bad because he could just blindly repeat what he/she read without understanding it) - its whether he/she can come up with a solution for the problem at all. In the interview you could still go into discussion about that approach then (what about undirected energy dissipation for contacting a thousands-of-km away satellite, and problems with time-multiplexing transmissions now on the satellite that has to answer individual requests vs broadcast etc.).