Rethinking GPS: Engineering next-gen location at Uber (2018)

https://www.uber.com/en-SE/blog/rethinking-gps/

by bmease • 4 years ago

263 61 4 years ago

Their internal app has ads for other Uber services? Oof.

gruez• 4 years ago

The article says "internal version of the Uber rider app", which makes me think it's some sort of internal/beta/debug build of the app that everyone else gets. In that case it makes sense that many of the features would stay the same, including stuff like ads.

maronato• 4 years ago

The “internal” app is essentially the same as the regular app. The difference is that it may receive beta features, there’s an easy “report bug” button and a side panel with diagnostics info, feature flags and other debugging tools.

tuananh• 4 years ago

"2018" post.

AlotOfReading• 4 years ago

I didn't even notice the date, thanks. The article presents it as if it was invented at Uber, but there's an identical family of techniques also called "shadow-matching" that have been known in the literature for like a decade. Many companies improve the raw GNSS fix with things like map-matching nowadays, but it was much less common even 5 years ago so this would have been fairly innovative back then.

g9yuayon• 4 years ago

Uber acquired a startup around 2015. It was that startup that was using shadow-matching and particle filtering to address the problems mentioned in the blog. The startup was founded by a bunch of UCLA PhDs who studied the problems, so I guess they had something innovative.

neilfrndes• 4 years ago

(2018)

KMnO4• 4 years ago

Cool, so it looks like they take the “raw” GPS location (after the GPS module does processing to spit out a lat/long) and applies statistical methods with a model of the actual 3D geometry. Seems like a smart way to improve the accuracy from “userspace”.

This reminds me of the Comma.ai project, Laika [0]. Since they have access to the raw GPS module data (Ie the actual timings of each received satellite transmitting), they can do things such as correcting for troposphere/ionosphere delays by looking up the relevant astro data as recorded by NASA and others.

[0] https://github.com/commaai/laika

skzv7• 4 years ago

You may be interested in knowing that Android has exposed raw GNSS measurements through public APIs [0,1] so anybody can build their own raw processing engines using techniques like the ones described in the article

[0] https://developer.android.com/guide/topics/sensors/gnss

[1] https://developer.android.com/reference/android/location/Gns...

myself248• 4 years ago

Is anyone actually doing that? I see a build of RTKLIB but it's not actually using the Android GNSS API, it's just using your Android phone as a processor to handle data coming from an external Ublox receiver. Aww.

c_o_n_v_e_x• 4 years ago

L5 GPS will address the multipath-in-urban-canyon problem that Uber worked on.

azinman2• 4 years ago

I don’t know much about L5. How does it do so?

LeoPanthera• 4 years ago

To oversimplify: It's on a different frequency and so will be subject to different forms of error. You can average the results of L1 and L5 to get a more accurate position.

skzv7• 4 years ago

It has a shorter wavelength so the correlation peaks are more narrow and hence more easily distinguishable. See this illustration [0] taken from this article [1]

[0] https://insidegnss-com.exactdn.com/wp-content/uploads/2021/0...

[1] https://insidegnss.com/end-game-for-urban-gnss-googles-use-o...

GekkePrutser• 4 years ago

It's not a perfect fix though. Even dual band multi network receivers will "jump around" a bit in deep canyons.

Example: https://hikingguy.com/hiking-gear/garmin-gpsmap-66sr-review-...

capableweb3• 4 years ago

Parent is talking about "urban canyons" which is just fancy wording for cities, while you're talking about actual canyons.

dataflow• 4 years ago

If you're curious which phones support L5, check out the table linked on this page (SCROLL DOWN to "GPSTest Database" for the up-to-date table, since the first one is out of date): https://barbeau.medium.com/9be4bbb83a7b

ciupicri2• 4 years ago

Also E5 Galileo [1]. It's such a shame that so few smartphones have support for dual frequency GPS and Galileo.

[1] https://gssc.esa.int/navipedia/index.php/Galileo_Signal_Plan

sorenjan2• 4 years ago

Is it really so few? Snapdragon got support for dual frequency in Snapdragon 855 released in 2018. Use the GPSTest app to see if your phone supports it.

https://github.com/barbeau/gpstest

faangiq• 4 years ago

How about make your drivers use semi decent phones that don’t lag GPS?

skzv7• 4 years ago

Google explores these techniques as well. They're critical to improving accuracy in urban areas where you don't have line of sight to satellites (this is why your GNSS (AKA GPS) location is terrible whenever you're in a city). Here's [0] a cool gif visualizing the principle of GNSS ray tracing taken from one of Google's blog posts [1]. Here's an article with more information about Google's techniques [2].

[0] https://1.bp.blogspot.com/-FskvGHx-IOc/X8qtZi1GUNI/AAAAAAAAP...

[1] https://android-developers.googleblog.com/2020/12/improving-...

[2] https://insidegnss.com/end-game-for-urban-gnss-googles-use-o...

ehsankia• 4 years ago

That seems much more useful, since it applies to all Android apps, whereas Uber's solution would be limited to their app only.

sieabah• 4 years ago

Almost like they wrote a blog article about it so others could learn from it.

If it were available to all android apps I don't know why Uber would go out of their way to reimplement it. So it must not be available to all apps and exclusive to Google maps and Waze

ilaksh2• 4 years ago

I think it says that FLP (Fused Location Provider) is not built in to Android.

yincrash• 4 years ago

FLP is an SDK available on Android devices with Google Play Services (https://developer.android.com/training/location/request-upda...). According to the blog post, it should theoretically be rolled out to any phone with Android 8 or later.

The Uber blog post is from 2018, and Google's implementation came in 2020.

bobsmooth• 4 years ago

What a brilliant use of all that satellite imagery.

eruleman• 4 years ago

Needs (2018) in the title.

jhatemyjob• 4 years ago

Was just in an Uber in Miami and the driver was telling me how the service stopped working for 3 hours a week ago. It seemed to be local to the area around Miami only, though. Anyone know if this is true?

sidcool• 4 years ago

This is an old article. Please label it likewise.

voz_• 4 years ago

Surprised I don't see Miles (https://www.linkedin.com/in/miles-detrixhe-32a979122/) on here - I remember the initial prototypes for this were his.

diebeforei485• 4 years ago

I'm curious if they'll make use of the L5 GPS band now that popular phones are getting it.

p1esk2• 4 years ago

What happened to the next gen gps technology, I thought it was supposed to be out by now. Centimeter level precision, much better urban (blocked by buildings) accuracy, etc?

tuukkah2• 4 years ago

It's not a single technology but multiple gradual improvements. E.g. since yesterday even iPhones have dual-frequency L5 GPS which improves accuracy in some situations: https://news.ycombinator.com/item?id=32790478

HatchedLake721• 4 years ago

GPS already has centimeter level precision. iPhone 14 will support the new L5 GPS signal

capableweb3• 4 years ago

What others said + it depends on your location, different GPS satellites serve different continents (usually), so GPS might work better/worse in Europe compared to South Africa (as an example).

p1esk2• 4 years ago

Wait, so with the new iphone I will be able to see my location on a map with this accuracy? So basically if a map resolves down to one foot I will have the location pinpointed to a foot from where I am? Currently it’s like 20 feet accuracy.

lalith_c• 4 years ago

https://news.ycombinator.com/item?id=16887276 Old HN thread

dang• 4 years ago

Thanks! Macroexpanded:

Rethinking GPS: Engineering Next-Gen Location at Uber - https://news.ycombinator.com/item?id=16887276 - April 2018 (102 comments)

Rethinking GPS: Engineering Next-Gen Location at Uber - https://news.ycombinator.com/item?id=17331841 - June 2018 (18 comments)

praveen9920• 4 years ago

Most of the Uber cabs work in urban settings where there are bunch of Wi-Fi enabled. Could they use the Wi-Fi to pinpoint the location instead of relying on GPS? Probably they can setup some relay nodes on their own for coverage.

datwelk• 4 years ago

No mention of iOS in the video or article. Anyone knows if Uber does something similar on iOS, and if Apple has done any similar efforts in system-level APIs like Google has?

zadwang• 4 years ago

Are there open data for this type of research? If someone would like to improve their algorithms.

sandworm101• 4 years ago

This should probably be called "use-specific gps optimization". These are ideas that improve accuracy for specific use cases (cars on roads) but may introduce errors for other users (people in buildings). We see this with googles driver-focused navigation whereby it always pulls you to a road, even though you may be well off the road.

Ive seen this come up in courts. A gps record will say that a person is traveling on highway X instead of parrallel street Y based on speed or direction of travel. When someone is doing something unussual (high speed in wrong direction) mapping software optimizations may go haywire. This is fine, so long as we all understand the difference between the underlying GPS track and a software-optimized track that incorporates logic beyond simple gps position.

Take the unussual situation of a large traffic accident. We dont want the EMT position to be reported as being on the sidewalk just because they are walking. Or after an earthquake. We dont want trapped survivor positions to change based on expected interfearance from tall buildings, buildings which might not be there anymore.

londons_explore3• 4 years ago

Urban canyons will be properly solved by using small phased array antennas for GPS reception. Then one can detect which signals are coming from the wrong direction and therefore must be reflections.

Phased array antennas also allow GPS-based compasses which should be far better than magnetic compasses which can be rather inaccurate.

Such phased array antennas are already coming into use for more throughput for 5G and WiFi use, and antenna sharing is feasible although not currently done commonly.

Rethinking GPS: Engineering next-gen location at Uber (2018)

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