171–180 of 296 posts
I work on the Android location team at Google, and I sent this article out to my team. GPS/GNSS is critical for accurate location/context, and there's still plenty of innovations happening in this field.
One of our directors is Frank Van Diggelen - none other than the professor who taught the Stanford GPS MOOC referenced by the article :) I'm sure he is going to appreciate seeing the course called out there!
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Chip manufacturing is even more prevalent. Why not ask a candidate about how silicon wafers are made?
Because that's a lot more obscure. A better example might be asking something like "what's the difference between cache and RAM" or "what is a CPU register", which I'm starting to think will still catch objections from some people on the grounds of it not being relevant to Javascript. Asking how GPS works (in general terms) is more like asking how the Internet works. Anyone who has "engineer" attached to their job ti…
The super-simple answer is correct, but I think if you asked in an interview people would try to give a complicated and wrong answer out of nerves.
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Can you say a little more about this? This is a topic I am interested in, and I was hoping that the OP went into it, but it didn't seem like it did.
The linked article does neatly, but they use 2D projection (so it's circles not spheres). Very simplified you use the broadcasted position + timestamp of multiple GPS satellites to find your location on the earth. So for a single satellite, you can (using time-in-flight of the signal) estimate the distance to that satellite at a point in time when you received its data. Once you know the distance D to that single sat…
Unfortunately, I don't understand. For example, check out this screenshot from the OP: https://i.imgur.com/9kh5tBi.png
If the satellites are above (the horizon/field of view), and you're intersecting spheres, it seems to me that you would have the best precision in the height direction and worse precision along the sphere. Am I missing something?
From the toy model it seems like if in addition to distance you could also get your angle to the landmark then you could get your position from a single landmark. Is that something which is practical? Knowing which angle a radio signal came from? It seems like if you had several receivers you could use the timings of when they receive a message to determine the approximate direction of the satellite in the sky. Given…
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I'll firmly disagree. I find logic questions, and how they solve a problem vastly more important than other aspects of the interview. I'm often looking for someone I can give a problem to and they return with a potential solution. That involves thinking through problems, how they work, how they can't work, etc. Asking someone how they think GPS works, or asking them a question about how they'd try to track down a def…
The overarching skillset that really smart people use everyday to explain how x works or investigate a customer issue is...google
This is why these questions are important. The skill set is logic and deduction not regurgitation of ideal solutions.
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It's about literally looking at it (in 3D) and guessing the exact position on the 2D map, which is easier closer to the landmarks. At least that's my interpretation.
Yeah, I suppose it’s like “you are a human standing on a flat plain looking at these 3 landmark towers. Where on the map are you? Intuitively you would be able to eyeball the angles between the landmarks, and eyeball the relative distances. I don’t think I’d draw a circle though. I’d probably have way less confidence for the landmark farther away and balloon out my estimate.
However, I do like the role GPS plays as a plot device in all kind of stories, where it's an active device, with GPS-enabled devices giving away position or there's no GPS in the wilderness, as mobile connections fail. So there are two versions of GPS, the popular plot device and the actual navigation device. (The more sinister version is that this has actually been planted as a cover-up for more realistic electronic…
Related: When I fly, I like to cache a map of the region I fly over on my phone, particularly the airport region at the destination. Then, you can hold your phone to the window for a few minutes and get a GPS fix, even if in airplane mode, because as you say GPS is purely passive. Then you can follow along nicely where you are, at the resolution you want. (Sure, many airlines have moving maps, but they're not as good…
