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GPS

ciechanow.ski

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Re: GPS

#281

Post by mhb »

dpark wrote: post #280
mhb wrote: post #262

Earlier quoted context omitted.

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?

The thread became about whether a good interview question for an engineer was how she thought GPS works. HeyLaughingBoy thinks that the qualities a question like that seeks to explore are irrelevant for a programming job.

I think that it is a good question for any engineer. One explanation for why HeyLaughingBoy might have disagreed was that HeyLaughingBoy was making a distinction between a programmer and an engineer.

I thought that highlighting the distinction between what HeyLaughingBoy wrote (programmer) and the parent (engineer) was a parsimonious way of expressing this.

Re: GPS

#282

Post by muunbo »

Lovely visualization! Reminds me of the principles used by Bret Victor to teach things well - allow the learner to play with time and space of the simulation so they can understand the system fully. Thank you for making this

Re: GPS

#283

Post by skzv »

zb wrote: post #257
skzv wrote: post #238

Earlier quoted context omitted.

Cool! Were you involved in GPS/localization R&D back then?

Yes, I was working for a company making standalone car navigation devices (remember those?), amongst other GPS-related things - I also worked on a lot of OEM GPS receivers. There was even a guy (not me!) who had written the firmware for a GPS receiver basically from scratch, so I got a look at everything from the very low level up to the navigation UI. At this point the iPhone hadn’t come out yet, but building data w…

Very cool. What are you up to these days?

My manager worked at Qualcomm back in the day and played a huge role in creating the first GNSS smartphone chipsets.

Likewise, I've learned a lot from him and other veterans in my org.

Re: GPS

#284

Post by jameshart »

marcellus23 wrote: post #270
jameshart wrote: post #263

Earlier quoted context omitted.

It’s not really relevant to how GPS works? It’s just scene setting an intuition for, crudely, how you might estimate your position relative to landmarks. If your take is then ‘well, he didn’t rigorously define how he derived the error bounds on crude position estimation, therefore all this stuff building into the level of precision GPS is capable of rests on a flimsy foundation of lies’, perhaps you are not the targe…

> well, he didn’t rigorously define how he derived the error bounds on crude position estimation or more correctly, he used an example and a diagram without every explaining how we should think about it. I think running into a nonsensical, unexplained diagram is a good heuristic for whether or not an article is worth reading — even if, in this case, it turns out the rest of the article is well-written.

Sounds to me like you ran into a strong counterexample that suggests it’s a terrible heuristic.

Re: GPS

#285

Post by uoaei »

jvanderbot wrote: post #18

> Naturally, large range uncertainty increases the ambiguity of position, but the relative position of the satellites also matters. If they aren’t well spread, the exactness of calculated location also suffers. (see the excellent example in OP) Fun tidbit, the resulting error is known for the system in closed form as Geometric Dilution of Precision, and is a 3x3 (edit: or 4+x4+ if you are estimating bias or quantitie…

Why is it called "Geometric Dilution of Precision" and not "covariance matrix"? In what ways is the former not the latter?

Re: GPS

#286

Post by kingnothing »

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.

Uber has an interesting approach to solving this issue: https://eng.uber.com/rethinking-gps/

Re: GPS

#287

Post by zb »

skzv wrote: post #283
zb wrote: post #257

Earlier quoted context omitted.

Yes, I was working for a company making standalone car navigation devices (remember those?), amongst other GPS-related things - I also worked on a lot of OEM GPS receivers. There was even a guy (not me!) who had written the firmware for a GPS receiver basically from scratch, so I got a look at everything from the very low level up to the navigation UI. At this point the iPhone hadn’t come out yet, but building data w…

Very cool. What are you up to these days? My manager worked at Qualcomm back in the day and played a huge role in creating the first GNSS smartphone chipsets. Likewise, I've learned a lot from him and other veterans in my org.

Cloud infrastructure - so basically I have gone right from one end of the scale spectrum (tiny GPS receivers) to the very opposite extreme :D

Re: GPS

#288

Post by terinjokes »

therealmarv wrote: post #179
FabHK wrote: post #161

Earlier quoted context omitted.

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…

I do that with OSMand on Android too. It's interesting if you fly on the window side.

Once I was flying in the middle section of economy, on a flight without in-flight WiFi, and accidentally opened Google Maps on my phone. I was shocked to find it managed to see enough GPS satellites to provide a lock, which matched the map in the seat back in front of me.

Re: GPS

#289

Post by kbart »

BatteryMountain wrote: post #244
coryfklein wrote: post #176

It's so depressing that – at some point in the future – I'm going to want a really clear and precise explanation of how GPS works and the likelihood that an internet search directs me to this excellent, clean, and ad-free blog is essentially nil.

Make a bookmark for it, let it sync to all your devices.

Cool, so now we are back to 1996 with Internet as curated lists.

Re: GPS

#290

Post by askvictor »

ninkendo wrote: post #261
askvictor wrote: post #222

Earlier quoted context omitted.

I wish this was standard in recipe webpages. It really makes a difference, and shows the author is thinking about their audience.

Adam Ragusea has a good video on why recipes aren't so easy to translate between imperial and metric: https://www.youtube.com/watch?v=TE8xg3d8dBg It comes down to the fact that the ingredients we buy from the stores near us tend to come in nice round numbers in our local measuring system, and recipes tend to be tailored to that. For example, "1 cup of shredded cheese and 1lb sausage" may translate precisely to "236.9…

For baking, precision is important, but subsequently most recipes are precisely specified, so the conversion should be followed pretty exactly. For most non-baking recipes, precisions is much less important, so a 'recipe translator' could either perform some rounding (maybe there should be a 'level of precision' metadata element for recipes), or, I could just do the rounding in my head and use my critical thinking facilities rather than following the recipe blindly.
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