5 ms·

The International Date Line and the 180-degree line of longitude have bitten a _lot_ of folks who don't think to test at the boundaries.

by _moof 3y ago

freyfogle 3y ago
We had a great example of this in a recent Geomob London talk: ask Google Maps to route from Wairiki, Fiji (-16.8048, 179.9893) to Welagi, Fiji (-16.7349, -179.9439), two villages on the coastal road of the same island and about 10km apart, but as you can see from the coordinates on opposite sides of the anti-meridian. You get "Sorry, we could not calculate driving directions from "Wairiki, Fiji" to "Welagi, Fiji" https://www.google.com/maps/dir/Wairiki,+Fiji/Welagi,+Fiji/@-16.7562483,179.9591553,12z/data=!3m1!4b1!4m14!4m13!1m5!1m1!1s0x6e1fe20547a57e5b:0xc78104c10808cd58!2m2!1d179.9918393!2d-16.8075135!1m5!1m1!1s0x71e004bf2cc89421:0x242b995ff2ed8932!2m2!1d-179.9083841!2d-16.705016!3e0?entry=ttu https://www.google.com/maps/dir/Wairiki,+Fiji/Welagi,+Fiji/@...
- mk_stjames 3y ago
  Interesting, is the ring road around Tavuki Island THE only road that falls on the anti-meridian, at all? A quick look along the line and it looks like it. It's wild that on google maps, even dropping a pin on the Tavuki road and trying to drag it across the line, it just stops, hitting this invisible wall. Something about this experience makes me want to go there....
  - seryoiupfurds 3y ago
    Wow, even zooming in and out on that island makes Google Maps skip into the middle of the ocean. Edit: and the nearby Rabi Island has a discontinuity at the meridian in map view. Zooming in on it in satellite view sent the map into a crazy refreshing state with flickering grid lines.
    - pests 3y ago
      These real-life effects by our decisions in technology sometimes half way around the world are very interesting to me. Similar to how some poeple are unlucky enough to live in their communities geographic center that becomes the default location for GPS lookups for that location.
      - defrost 3y ago
        There was US mapping software (not the international scientific survey semi open source stuff, commercial mapping for US public) in the late 1980s and 1990s that actually had positive longitude displays over the US mainland so that their users didn't have to think in negative numbers. As I noted elsewhere in this thread, large swathes of US software couldn't handle mapping computations that straddled the date line and it's breathtaking that this is still an issue today.
- defrost 3y ago
  It astounds me that this is still a problem in 2023. I company I coded for surveyed the entire Fiji region in 1997, drafting aircraft at 80m ground clearance in long lines across both sides of the 180 longitude line. Every single bit of commercial US GIS software available at the time was garbage and failed to correctly compute line lengths that straddled the 180 longitude line, areas of rectangles that did the same, correctly polygon mask etc. Fortuneately we had in house software (that had the same flaws, considering it originated from Sunnydale, California) and source code so this became Yet Another Patch I had to write in on the fly in the midst of everything else to move forward. I wrote issue tickets on this to ArcView | ESRI (of the day), the open GIS groups of the day, and raised it with anybody on relevant IRC boards | early reddit who was talking about their aircraft control software, etc. I haven't thought about that for 14 odd years now .. but I really thought the base libraries in Google Maps would correctly handle geodesic geometry by now.
  - jacquesm 3y ago
    I'll bet if SV wasn't such a hotspot that such things would be handled better. You can't dogfood this if you're in Mountain View and chances are that the intersection of 'people working on Google Maps' and 'people that use Google Maps in Fiji' is empty.
    - dmix 3y ago
      That would make sense if Google Maps wasn't 18yrs old, but I don't really have opinions on that sort of thing as I've never worked for a large tech company on a mature product. Maybe there's not much motivation to try that hard after a certain time.
      - jacquesm 3y ago
        Yes, I think I should have made my point better: if you can't dogfood it and the population affected is small people just don't care, especially if there is zero economic incentive. It sucks that it is like that.
- ReactiveJelly 3y ago
  Weird considering that Google maintains the S2 geometry lib which is supposed to handle things better than naive lat/long
- SoftTalker 3y ago
  > "Sorry, we could not calculate driving directions from "Wairiki, Fiji" to "Welagi, Fiji" And how many potential users does this affect? Enough for Google to spend 10 seconds worrying about it?
- heeen2 3y ago
  I can't get any routing on that island at all, even within the same settlement
PaulHoule 3y ago
I was working on a program that sales managers would use to divide sales territories up between salespeople and one feature was the ability to select all territories a certain distance from a point and using the most simplistic algorithm the code would crash if the circle crosses the 180 line so we had to use a somewhat more complicated algorithm than we first thought for this, even though all of the U.S. is one one side of it
- krisoft 3y ago
  > even though all of the U.S. is one one side of it Guam would beg to differ. :)
  - PaulHoule 3y ago
    We didn't have Guam in our list of territories as I don't think our customers had sales offices there or if they did they already knew who was going to serve it.
    - tomcam 3y ago
      Get outta here, Guam—hater. Kidding, people!
dheera 3y ago
Why didn't they just use UTC for everything? No time zone no bite
- defrost 3y ago
  It's a longitude issue, not a time zone problem. The distance along the zero latitude equator from -179.99 W to +179.99 E should be relatively easy to compute and yet a large proportion of software in the mapping domain screws that up - even software that controls drones and| used by commercial pilots in the US, etc.
  - doctor_eval 3y ago
    Ok so to clarify it’s not the international date line but the latitude? Which makes more sense to me because the international date line is not actually a straight line.
    - defrost 3y ago
      > to clarify it’s not the international date line but the latitude? Longitude. The vertical one that goes from negative to positive at 180 Longitude East or West. Maybe you should get a map out and have a look.
      - doctor_eval 3y ago
        Right. I do know the difference between latitude and longitude; I just mistyped. I was working in Samoa when they changed the date to align with NZ time, so am quite familiar with the region.
        defrost 3y ago
        No drama, I'm more and more prone to using the wrong word, adding a 'not', and totally screwing up comments now that I've passed 60. I mainly intended to clarify for any readers rather than castigate you, and after the initial remark about time zone I got a little blunt. ( FWIW I made several mistakes in this comment and had to edit twice )

The International Date Line and the 180-degree line of longitude have bitten a _lot_ of folks who don't think to test at the boundaries.

by _moof 3y ago

The International Date Line and the 180-degree line of longitude have bitten a _lot_ of folks who don't think to test at the boundaries.

freyfogle 3y ago

We had a great example of this in a recent Geomob London talk: ask Google Maps to route from Wairiki, Fiji (-16.8048, 179.9893) to Welagi, Fiji (-16.7349, -179.9439), two villages on the coastal road of the same island and about 10km apart, but as you can see from the coordinates on opposite sides of the anti-meridian. You get "Sorry, we could not calculate driving directions from "Wairiki, Fiji" to "Welagi, Fiji" https://www.google.com/maps/dir/Wairiki,+Fiji/Welagi,+Fiji/@-16.7562483,179.9591553,12z/data=!3m1!4b1!4m14!4m13!1m5!1m1!1s0x6e1fe20547a57e5b:0xc78104c10808cd58!2m2!1d179.9918393!2d-16.8075135!1m5!1m1!1s0x71e004bf2cc89421:0x242b995ff2ed8932!2m2!1d-179.9083841!2d-16.705016!3e0?entry=ttu https://www.google.com/maps/dir/Wairiki,+Fiji/Welagi,+Fiji/@...

mk_stjames 3y ago
Interesting, is the ring road around Tavuki Island THE only road that falls on the anti-meridian, at all? A quick look along the line and it looks like it. It's wild that on google maps, even dropping a pin on the Tavuki road and trying to drag it across the line, it just stops, hitting this invisible wall. Something about this experience makes me want to go there....
- seryoiupfurds 3y ago
  Wow, even zooming in and out on that island makes Google Maps skip into the middle of the ocean. Edit: and the nearby Rabi Island has a discontinuity at the meridian in map view. Zooming in on it in satellite view sent the map into a crazy refreshing state with flickering grid lines.
  - pests 3y ago
    These real-life effects by our decisions in technology sometimes half way around the world are very interesting to me. Similar to how some poeple are unlucky enough to live in their communities geographic center that becomes the default location for GPS lookups for that location.
    - defrost 3y ago
      There was US mapping software (not the international scientific survey semi open source stuff, commercial mapping for US public) in the late 1980s and 1990s that actually had positive longitude displays over the US mainland so that their users didn't have to think in negative numbers. As I noted elsewhere in this thread, large swathes of US software couldn't handle mapping computations that straddled the date line and it's breathtaking that this is still an issue today.
defrost 3y ago
It astounds me that this is still a problem in 2023. I company I coded for surveyed the entire Fiji region in 1997, drafting aircraft at 80m ground clearance in long lines across both sides of the 180 longitude line. Every single bit of commercial US GIS software available at the time was garbage and failed to correctly compute line lengths that straddled the 180 longitude line, areas of rectangles that did the same, correctly polygon mask etc. Fortuneately we had in house software (that had the same flaws, considering it originated from Sunnydale, California) and source code so this became Yet Another Patch I had to write in on the fly in the midst of everything else to move forward. I wrote issue tickets on this to ArcView | ESRI (of the day), the open GIS groups of the day, and raised it with anybody on relevant IRC boards | early reddit who was talking about their aircraft control software, etc. I haven't thought about that for 14 odd years now .. but I really thought the base libraries in Google Maps would correctly handle geodesic geometry by now.
- jacquesm 3y ago
  I'll bet if SV wasn't such a hotspot that such things would be handled better. You can't dogfood this if you're in Mountain View and chances are that the intersection of 'people working on Google Maps' and 'people that use Google Maps in Fiji' is empty.
  - dmix 3y ago
    That would make sense if Google Maps wasn't 18yrs old, but I don't really have opinions on that sort of thing as I've never worked for a large tech company on a mature product. Maybe there's not much motivation to try that hard after a certain time.
    - jacquesm 3y ago
      Yes, I think I should have made my point better: if you can't dogfood it and the population affected is small people just don't care, especially if there is zero economic incentive. It sucks that it is like that.
ReactiveJelly 3y ago
Weird considering that Google maintains the S2 geometry lib which is supposed to handle things better than naive lat/long
SoftTalker 3y ago
> "Sorry, we could not calculate driving directions from "Wairiki, Fiji" to "Welagi, Fiji" And how many potential users does this affect? Enough for Google to spend 10 seconds worrying about it?
heeen2 3y ago
I can't get any routing on that island at all, even within the same settlement

PaulHoule 3y ago

I was working on a program that sales managers would use to divide sales territories up between salespeople and one feature was the ability to select all territories a certain distance from a point and using the most simplistic algorithm the code would crash if the circle crosses the 180 line so we had to use a somewhat more complicated algorithm than we first thought for this, even though all of the U.S. is one one side of it

krisoft 3y ago
> even though all of the U.S. is one one side of it Guam would beg to differ. :)
- PaulHoule 3y ago
  We didn't have Guam in our list of territories as I don't think our customers had sales offices there or if they did they already knew who was going to serve it.
  - tomcam 3y ago
    Get outta here, Guam—hater. Kidding, people!

dheera 3y ago

Why didn't they just use UTC for everything? No time zone no bite

defrost 3y ago
It's a longitude issue, not a time zone problem. The distance along the zero latitude equator from -179.99 W to +179.99 E should be relatively easy to compute and yet a large proportion of software in the mapping domain screws that up - even software that controls drones and| used by commercial pilots in the US, etc.
- doctor_eval 3y ago
  Ok so to clarify it’s not the international date line but the latitude? Which makes more sense to me because the international date line is not actually a straight line.
  - defrost 3y ago
    > to clarify it’s not the international date line but the latitude? Longitude. The vertical one that goes from negative to positive at 180 Longitude East or West. Maybe you should get a map out and have a look.
    - doctor_eval 3y ago
      Right. I do know the difference between latitude and longitude; I just mistyped. I was working in Samoa when they changed the date to align with NZ time, so am quite familiar with the region.
      - defrost 3y ago
        No drama, I'm more and more prone to using the wrong word, adding a 'not', and totally screwing up comments now that I've passed 60. I mainly intended to clarify for any readers rather than castigate you, and after the initial remark about time zone I got a little blunt. ( FWIW I made several mistakes in this comment and had to edit twice )