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GPS

ciechanow.ski

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Re: GPS

#271

Post by randomswede »

Unklejoe wrote: post #132
daenz wrote: post #121

Earlier quoted context omitted.

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…

"Assume you are on a relatively typical unix system, you type `ls -l` and press return, walk me through what happens in as much detail as you're comfortable with."

A decent candidate will give me 5-10 minutes of delving into various parts of "unix processes", maybe "dynamic linking", most probably a bit of "file system" by judicious use of "could you explain that in more detail" or "how does X work".

A truly excellent candidate will have me taking notes for 25-30 minutes, while they pre-answer all my followup questions, go through process creation, dynamic linking, file system API, filesystem internals, maybe some disk layout, process termination and signal handling.

Out of maybe 120 candidates I've asked that question, one (maybe two) have answered it so fully on their own that I did not have to ask any followup questions. And pretty much exhausted my question graph, so once done we could pivot to "do you have any questions for me?".

Re: GPS

#272

Post by [deleted] »

jpindar wrote: post #265
rvba wrote: post #236

Earlier quoted context omitted.

How many satelites are tracked by a typical android phone? 4? Or more? Can it track both GPS and other systems like glonass at the same time?

Mine's detecting 20 at the moment, and using 14 of those. This varies slightly from minute to minute. Many GPS apps display this data.

[deleted]

Re: GPS

#273

Post by Bost »

daenz wrote: post #187
Youden wrote: post #163

Earlier quoted context omitted.

Again, that's not necessarily how that's intended. The observation on its own is just an observation, it doesn't indicate anything about how interview performance was evaluated. For example when I interview, I have a question related to chess, which requires a basic understanding of how the pieces move. I was amazed that even engineers don't understand the basic movement rules of chess. However as far as the intervie…

As an interviewer, where there's a huge power imbalance, why even stray into the territory where candidate can easily perceive a disadvantage for not having totally unrelated knowledge? A candidate will feel like their lack of chess knowledge, or GPS knowledge, hurt them if they didn't perform well. Why not just ask questions that are relevant to the work they will be doing? Maybe you don't realize just how stressful…

> you don't realize just how stressful interviews are to some people

Getting stressed too much about a job interview may be a sign of overcommitment. And I believe you're not looking for a guy ready to go over corpses.

Re: GPS

#274

Post by MarkSweep »

mleonhard wrote: post #208
skzv wrote: post #171

Amazing work. 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 t…

There are certain streets in downtown SF where Android (and iOS) location always suddenly jumps to a block away. Navigation apps then direct drivers to make incorrect turns or even dangerous turns like turning the wrong way onto a one-way street. It seems to me that your software could prevent this error.

Japan solved this problem in Tokyo by adding some extra satellites:

https://en.wikipedia.org/wiki/Quasi-Zenith_Satellite_System

Re: GPS

#275

Post by Matumio »

coryfklein wrote: post #185
amelius wrote: post #181

Earlier quoted context omitted.

I searched for an excellent, clear and precise explanation of GPS that is clean and ad-free, and landed on your comment.

You may be on to something here. With GPT-3 you could improve the quality of the responses by starting with a prompt like, "You're a well-educated and very helpful individual". Maybe internet searches can be improved by changing the search from "how gps works" to "excellent, clear, and precise explanation of gps"?

Searching for "TechA vs TechB" was also a great trick. Until the SEO people noticed. They also have access to GPT-3 now to generate their auxiliary "content".

I think we need web search to move towards something more reputation-based. (Based on sites like HN, Reddit, StackOverflow, etc. that don't allow to easily fake high reputation. Or some kind of trust network starting from all your social accounts' subscriptions/follows and spreading your trust far outwards.)

Re: GPS

#276

Post by myself248 »

michaelt wrote: post #254
myself248 wrote: post #198

Earlier quoted context omitted.

It's been said that week number rollover occupies a "sweet spot of awfulness" where it happens infrequently enough that it doesn't get much testing, but often enough to impact equipment deployed in the real world. The designers of GPS either should've made it use like 64 weeks so WNRO would happen constantly and we'd have to get good at handling it, or 32768 weeks so we could ignore it for the entire life of the syst…

> It's been said that week number rollover occupies a "sweet spot of awfulness" It's even worse than that: The traditional way of handling week number rollover is a rollover count in nonvolatile memory, incremented every time a rollover is seen (for a standalone receiver there's no other source for how many rollovers there have been) So a griefer with a software-defined radio can radio out repeated week number rollov…

Perhaps traditional in devices without a UI. My car's stereo (which is where the GPS/nav functions also live) has an epoch dropdown in the settings menu.

I presume you're referencing https://users.ece.cmu.edu/~dbrumley/pdf/Nighswander%2520et%2...

Re: GPS

#277

Post by perlgeek »

SomewhatLikely wrote: post #164

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…

> Is that something which is practical?

Not really.

Determining the angle of a microwave signal requires a pretty big receiver dish (or an array of receivers, at least).

The wavelength of the GPS L1 band is 19cm, you'd need (roughly) something of at least 10x that size to get a good sense of where a signal is coming from, so on the order of 2m.

A single good antenna and sensitive amplifier gets you a fix on more satellites, which provides good accuracy with less space and hardware used.

Re: GPS

#278

Post by guru4consulting »

skzv wrote: post #235
tda wrote: post #232

Earlier quoted context omitted.

I wonder how the inventors of GPS would have responded if back in the early nineties you had suggested to just add a map of all the worlds high buildings to the GPS receiver.

I think we're doing all sorts of things now that people decades ago thought were simply impossible!

seems almost impossible even now.. awesome and inspiring work. Kudos to all of you

Re: GPS

#279

Post by masswerk »

elxr wrote: post #260
masswerk wrote: post #27

Earlier quoted context omitted.

Yes, great educational content and great interactive animations! (Also, a constant reminder to learn WebGL. ;-) )

This article just pushed WebGL to the top of my to-learn list! Those graphics were lovely, and makes me realize how underutilized this stuff is in the modern web.

The really neat stuff is in the details, like when the elastic rope curls. – We have somewhat forgotten how important these details are, even in infographics. Let's call this "interactive texture".

Re: GPS

#280

Post by dpark »

mhb wrote: post #262
dpark wrote: post #139

Earlier quoted context omitted.

What kind of “engineers”? I’m not aware of most engineers going through this sort of interview. Mostly just software engineers who are indeed programmers even if they get uppity about the title

OK, I'll play. Some qualities that are valuable in an engineer are curiosity, creativity, and general knowledge. If your nomenclature has a programmer as a software engineer and a software engineer as an engineer, then these qualities are also valuable in programmers. If you ask an interviewee how GPS works and he says something about the cell phone sending signals to a satellite, you would want to pursue that furthe…

Let me rephrase my question.

Are you nitpicking the difference between a different engineer and a programmer or are you interviewing a different sort of engineer?

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