5 ms·

Interesting that it’s not confirmed if the SR-71 flew in the Southern Hemisphere. Would be a very bold design if it didn’t and the system wasn’t designed for it

Interesting that it’s not confirmed if the SR-71 flew in the Southern Hemisphere. Would be a very bold design if it didn’t and the system wasn’t designed for it.

fidotron 3y ago
The F22 had an unintentional problem of being unable to cross the international date line, which was discovered when attempting to fly from Hawaii to Japan. Given that it may very well be better to assume that anything untested doesn't work at all and to live within those restrictions.
- tlrobinson 3y ago
  “Unable”? How did this manifest?! > Given that it may very well be better to assume that anything untested doesn't work at all and to live within those restrictions. There are an infinite number of untested cases though. Figuring out the important ones is the hard part, otherwise they likely would have been identified and fixed in development.
  - sampo 3y ago
    > “Unable”? How did this manifest?! https://news.ycombinator.com/item?id=4541501 https://news.ycombinator.com/item?id=4541501
  - eastbound 3y ago
    Would it invert North and South after crossing the line? No, that’s the story of the Soviet bomber that took off the wrong way from the airstrip in a secret night mission, and ended up 180° in Iran. Fortunately the two iranian jetfighters supposed to down it, ended up chasing each other. Real world is hilarious. https://youtu.be/i-bdJF6TUFs https://youtu.be/i-bdJF6TUFs
- omginternets 3y ago
  Something about non-monotonic software clocks?
- _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.
- jvm___ 3y ago
  The space shuttle was untested in flying over the new year between December and January. It needed a clock reset and they weren't about to test that on orbit.
  - phire 3y ago
    I assume they would have gotten around to testing it if the space shuttle program ever got anywhere near its planned operational capacity. But with only 4 operational shuttles, ~20 days maximum ndurance and only 5-10 flights per year, it was simply enough to just avoid scheduling any mission in the latter half of December. (Though, I notice STS-103 departed for an 8 day mission on December 19th 1999. That was cutting it close)
- nradov 3y ago
  There have supposedly also been avionics issues with flying at negative altitude. Israel has an airbase in the Dead Sea which is located below sea level. https://avgeekery.com/challenge-flying-sea-level/ https://avgeekery.com/challenge-flying-sea-level/
stevenwoo 3y ago
It says they did have capability to navigate in Southern hemisphere though it might be implied one had to use two stars only visible in southern hemisphere.
eastbound 3y ago
Is it true that military branches (navy, airforce) from around equator use a grid-square reference system for radars and have issues when going further north, while triangle-based reference systems are a really good model in polar countries that doesn’t scale well when going South? It’s a problem so predictable that I can’t believe I have been told the truth, and it’s impossible to find the right keywords to search that on Google ;)
- chipsa 3y ago
  The military does use a grid square reference system, Military Grid Reference System (MGRS), and to resolve the issues when sufficiently far north, the grid squares stop being aligned with the latitudes and longitudes, but rather just sit lined up with the 0/90/270/180 longitudes, as a sort of circular cap cut out of grid paper. (Properly speaking, it's Universal Transverse Mercator (which is a series of 60 Mercator projections) between 80S and 84N, and Universal Polar Stereographic near the poles).
  - freyfogle 3y ago
    Best bit of weirdness about UTM is the exception made for zone 32V so that Norway fits into a single zone, see: https://en.osm.town/@opencage/109694749637123570 https://en.osm.town/@opencage/109694749637123570
    - chipsa 3y ago
      There's a similar weirdness for Svalbard, which results in 32/34/36X not existing.
someplaceguy 3y ago
According to the documentation of the Astro-Nav System, it is designed to operate in polar areas [1]. [1] https://airandspace.si.edu/webimages/collections/full/NAS-14V2%20ANS%20System.pdf https://airandspace.si.edu/webimages/collections/full/NAS-14...

Interesting that it’s not confirmed if the SR-71 flew in the Southern Hemisphere. Would be a very bold design if it didn’t and the system wasn’t designed for it.

fidotron 3y ago

The F22 had an unintentional problem of being unable to cross the international date line, which was discovered when attempting to fly from Hawaii to Japan. Given that it may very well be better to assume that anything untested doesn't work at all and to live within those restrictions.

tlrobinson 3y ago
“Unable”? How did this manifest?! > Given that it may very well be better to assume that anything untested doesn't work at all and to live within those restrictions. There are an infinite number of untested cases though. Figuring out the important ones is the hard part, otherwise they likely would have been identified and fixed in development.
- sampo 3y ago
  > “Unable”? How did this manifest?! https://news.ycombinator.com/item?id=4541501 https://news.ycombinator.com/item?id=4541501
- eastbound 3y ago
  Would it invert North and South after crossing the line? No, that’s the story of the Soviet bomber that took off the wrong way from the airstrip in a secret night mission, and ended up 180° in Iran. Fortunately the two iranian jetfighters supposed to down it, ended up chasing each other. Real world is hilarious. https://youtu.be/i-bdJF6TUFs https://youtu.be/i-bdJF6TUFs
omginternets 3y ago
Something about non-monotonic software clocks?
_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.
jvm___ 3y ago
The space shuttle was untested in flying over the new year between December and January. It needed a clock reset and they weren't about to test that on orbit.
- phire 3y ago
  I assume they would have gotten around to testing it if the space shuttle program ever got anywhere near its planned operational capacity. But with only 4 operational shuttles, ~20 days maximum ndurance and only 5-10 flights per year, it was simply enough to just avoid scheduling any mission in the latter half of December. (Though, I notice STS-103 departed for an 8 day mission on December 19th 1999. That was cutting it close)
nradov 3y ago
There have supposedly also been avionics issues with flying at negative altitude. Israel has an airbase in the Dead Sea which is located below sea level. https://avgeekery.com/challenge-flying-sea-level/ https://avgeekery.com/challenge-flying-sea-level/

stevenwoo 3y ago

It says they did have capability to navigate in Southern hemisphere though it might be implied one had to use two stars only visible in southern hemisphere.

eastbound 3y ago

Is it true that military branches (navy, airforce) from around equator use a grid-square reference system for radars and have issues when going further north, while triangle-based reference systems are a really good model in polar countries that doesn’t scale well when going South? It’s a problem so predictable that I can’t believe I have been told the truth, and it’s impossible to find the right keywords to search that on Google ;)

chipsa 3y ago
The military does use a grid square reference system, Military Grid Reference System (MGRS), and to resolve the issues when sufficiently far north, the grid squares stop being aligned with the latitudes and longitudes, but rather just sit lined up with the 0/90/270/180 longitudes, as a sort of circular cap cut out of grid paper. (Properly speaking, it's Universal Transverse Mercator (which is a series of 60 Mercator projections) between 80S and 84N, and Universal Polar Stereographic near the poles).
- freyfogle 3y ago
  Best bit of weirdness about UTM is the exception made for zone 32V so that Norway fits into a single zone, see: https://en.osm.town/@opencage/109694749637123570 https://en.osm.town/@opencage/109694749637123570
  - chipsa 3y ago
    There's a similar weirdness for Svalbard, which results in 32/34/36X not existing.

someplaceguy 3y ago

According to the documentation of the Astro-Nav System, it is designed to operate in polar areas [1]. [1] https://airandspace.si.edu/webimages/collections/full/NAS-14V2%20ANS%20System.pdf https://airandspace.si.edu/webimages/collections/full/NAS-14...