7 ms·

It's crazy to read this, for the same reason that maps used to be military secrets; accurate bathymetric data is a huge deal for modern battlespace preparation.

It's crazy to read this, for the same reason that maps used to be military secrets; accurate bathymetric data is a huge deal for modern battlespace preparation. And it'll probably be impactful in all sorts of exciting ways just like Google Earth was when it released. Hopefully it doesn't experience too much interference from the usual suspects, like with the requirements that GPS maps be offset from reality. Given the large extraterritorial sea claims pushed by the same, it could interfere with a large geographic area.

medellin 3y ago
Can you explain “GPS maps offset from reality” or what would i have to look up to learn more? I see for china some into about random offsets but couldn’t find anything else.
- ysofunny 3y ago
  the mathematics of cartographic projections possibly but this information was really a military secret not that long ago. same as cryptography is right now! which annoys me personally becuase I wish to learn more/better about the mathematics behind information technology and cryptography. but this is considered 'sensitive' understanding so the quantity of people that are ever taught this stuff is tightly controlled; not to say that it's difficult stuff to begin with and any efforts to make it more widespread and accessible are often derailed in education comitees and so on. but I should stop before I get any more paranoid
  - 8note 3y ago
    This information is part of why the US missiles can hit their targets precisely and why Soviet ones could not. you lose accuracy dead reckoning when you don't have good corrections for the earth's gravity at your current location
    - pyinstallwoes 3y ago
      how much does earth's gravity fluctuate by location?
      - mschuster91 3y ago
        Quite a lot, at least at the weight and speed scale a missile operates on. The biggest source of gravity force difference is the distance between the equator / pole [1], and altitude (both in terms of altitude in reference to the planet core as well as altitude in reference to ground, e.g. due to the mass of a mountain range) also adds jitter [2]. On top of that, dead-reckoning is disturbed by aerodynamic effects such as wind, as well as drift from the gyro compass itself... a fine-detailed gravity effect map can be used to compensate for both of that, and adding imagery maps and radar/laser distance measuring is even better. To add even more context... that is the reason why Germany's Chancellor Scholz is refusing to deliver TAURUS long range missiles to Ukraine. TAURUS owes its significant increase in precision over Storm Shadow / SCALP (UK/FR equivalent) to that kind of sensor aids, but the assistance dataset aka the photogrammetry, gravity and height maps of the flight route must be individually created and loaded into the missile as part of the mission preparation. As you can imagine this kind of precision information is stuff that we really don't want to get leaked to Russia so we can't (or don't want to) deliver the systems for programming to Ukraine where it might get stolen/diverted to Russia, so Scholz is afraid that the necessary direct cooperation of German Bundeswehr soldiers with Ukrainian soldiers might be seen as an act of war of Germany by Putin. (Complete horse dung if you ask me, but I can understand where he's coming from) [1] https://www.wired.com/story/do-you-weigh-more-at-the-equator-or-at-the-north-pole/ https://www.wired.com/story/do-you-weigh-more-at-the-equator... [2] https://physics.stackexchange.com/a/652759 https://physics.stackexchange.com/a/652759
        pyinstallwoes 3y ago
        Does it vary at the location or is it constant? Basically, is it more like a fluid (air) or fixed because of mass?
      - naavis 3y ago
  - AlotOfReading 3y ago
    The details of specific implementations are sometimes considered secret, but broadly speaking the mathematics of both projections and cryptography are extremely public. For example, GCJ-02 (the projection being obliquely referenced by the GP) is just WGS-84 + "noise". For cryptography, you can read any of the excellent textbooks and educational resources available (e.g. [0]). [0] http://www.cs.umd.edu/%7Ejkatz/imc.html http://www.cs.umd.edu/%7Ejkatz/imc.html
    - ysofunny 3y ago
      i'm not supposed to say this, but my above paranoia is but a coping mechanism to deal with the harsh truth that I just cannot for the life of me completely understand any of those ideas no matter how well they're explained
      - mxkopy 3y ago
        It would make for a good sci fi novel, but yeah. Cryptography is cutthroat in the sense that if you’re even a little imprecise people can and will break your scheme. At some level of development the material will just filter out people from learning it.
- rdlw 3y ago
  I think the comment you replied to is just talking about the government of China. Try looking at China on Google Maps in satellite view.
  - bragr 3y ago
    Specifically look along the border with other countries where the offset is obvious. https://en.wikipedia.org/wiki/Restrictions_on_geographic_data_in_China#GPS_shift_problem https://en.wikipedia.org/wiki/Restrictions_on_geographic_dat...
- QuarterReptile 3y ago
  Others have already answered, but yes, I'm referring to China. Check out Google maps in any Chinese city; I've never seen one without the offsets. You can read about the general spec for the obfuscation and also about fines and arrests for illegal mapping.
wolverine876 3y ago
> accurate bathymetric data is a huge deal for modern battlespace preparation Their resolution is "all features 100 meters or larger", so better than nothing but not useful for manuevering your submarine.
- deleted 3y ago
  [deleted]
- QuarterReptile 3y ago
  100m isn't especially big. Significantly less than turning radius for most ships, and laughably small compared to stopping distance. Having said that, maneuvering is only one problem among many.
  - wolverine876 3y ago
    Obstacles smaller than 100m can wreck your sub.
    - _carbyau_ 3y ago
      Well yeah. But trees can wreck my face too. I'd still want a good contour map if I were to go wandering into the wilderness. A good map can tell you about the possibilities of the environment, but it's always inferior to looking at it yourself.
    - chmod775 3y ago
      So can obstacles smaller than 50cm. What resolution should we aim for?
      - QuarterReptile 3y ago
        I'm thoroughly nerd-sniped by your username. Is there something special about those permissions?
        3y ago
sph 3y ago
> It's crazy to read this, for the same reason that maps used to be military secrets Reminds me of the Map Men episode "Why does Russia have the best maps of Britain?" - https://www.youtube.com/watch?v=_bqzwsM6eoQ https://www.youtube.com/watch?v=_bqzwsM6eoQ

medellin 3y ago

Can you explain “GPS maps offset from reality” or what would i have to look up to learn more? I see for china some into about random offsets but couldn’t find anything else.

ysofunny 3y ago
the mathematics of cartographic projections possibly but this information was really a military secret not that long ago. same as cryptography is right now! which annoys me personally becuase I wish to learn more/better about the mathematics behind information technology and cryptography. but this is considered 'sensitive' understanding so the quantity of people that are ever taught this stuff is tightly controlled; not to say that it's difficult stuff to begin with and any efforts to make it more widespread and accessible are often derailed in education comitees and so on. but I should stop before I get any more paranoid
- 8note 3y ago
  This information is part of why the US missiles can hit their targets precisely and why Soviet ones could not. you lose accuracy dead reckoning when you don't have good corrections for the earth's gravity at your current location
  - pyinstallwoes 3y ago
    how much does earth's gravity fluctuate by location?
    - mschuster91 3y ago
      Quite a lot, at least at the weight and speed scale a missile operates on. The biggest source of gravity force difference is the distance between the equator / pole [1], and altitude (both in terms of altitude in reference to the planet core as well as altitude in reference to ground, e.g. due to the mass of a mountain range) also adds jitter [2]. On top of that, dead-reckoning is disturbed by aerodynamic effects such as wind, as well as drift from the gyro compass itself... a fine-detailed gravity effect map can be used to compensate for both of that, and adding imagery maps and radar/laser distance measuring is even better. To add even more context... that is the reason why Germany's Chancellor Scholz is refusing to deliver TAURUS long range missiles to Ukraine. TAURUS owes its significant increase in precision over Storm Shadow / SCALP (UK/FR equivalent) to that kind of sensor aids, but the assistance dataset aka the photogrammetry, gravity and height maps of the flight route must be individually created and loaded into the missile as part of the mission preparation. As you can imagine this kind of precision information is stuff that we really don't want to get leaked to Russia so we can't (or don't want to) deliver the systems for programming to Ukraine where it might get stolen/diverted to Russia, so Scholz is afraid that the necessary direct cooperation of German Bundeswehr soldiers with Ukrainian soldiers might be seen as an act of war of Germany by Putin. (Complete horse dung if you ask me, but I can understand where he's coming from) [1] https://www.wired.com/story/do-you-weigh-more-at-the-equator-or-at-the-north-pole/ https://www.wired.com/story/do-you-weigh-more-at-the-equator... [2] https://physics.stackexchange.com/a/652759 https://physics.stackexchange.com/a/652759
      - pyinstallwoes 3y ago
        Does it vary at the location or is it constant? Basically, is it more like a fluid (air) or fixed because of mass?
    - naavis 3y ago
- AlotOfReading 3y ago
  The details of specific implementations are sometimes considered secret, but broadly speaking the mathematics of both projections and cryptography are extremely public. For example, GCJ-02 (the projection being obliquely referenced by the GP) is just WGS-84 + "noise". For cryptography, you can read any of the excellent textbooks and educational resources available (e.g. [0]). [0] http://www.cs.umd.edu/%7Ejkatz/imc.html http://www.cs.umd.edu/%7Ejkatz/imc.html
  - ysofunny 3y ago
    i'm not supposed to say this, but my above paranoia is but a coping mechanism to deal with the harsh truth that I just cannot for the life of me completely understand any of those ideas no matter how well they're explained
    - mxkopy 3y ago
      It would make for a good sci fi novel, but yeah. Cryptography is cutthroat in the sense that if you’re even a little imprecise people can and will break your scheme. At some level of development the material will just filter out people from learning it.
rdlw 3y ago
I think the comment you replied to is just talking about the government of China. Try looking at China on Google Maps in satellite view.
- bragr 3y ago
  Specifically look along the border with other countries where the offset is obvious. https://en.wikipedia.org/wiki/Restrictions_on_geographic_data_in_China#GPS_shift_problem https://en.wikipedia.org/wiki/Restrictions_on_geographic_dat...
QuarterReptile 3y ago
Others have already answered, but yes, I'm referring to China. Check out Google maps in any Chinese city; I've never seen one without the offsets. You can read about the general spec for the obfuscation and also about fines and arrests for illegal mapping.

wolverine876 3y ago

> accurate bathymetric data is a huge deal for modern battlespace preparation Their resolution is "all features 100 meters or larger", so better than nothing but not useful for manuevering your submarine.

deleted 3y ago
[deleted]
QuarterReptile 3y ago
100m isn't especially big. Significantly less than turning radius for most ships, and laughably small compared to stopping distance. Having said that, maneuvering is only one problem among many.
- wolverine876 3y ago
  Obstacles smaller than 100m can wreck your sub.
  - _carbyau_ 3y ago
    Well yeah. But trees can wreck my face too. I'd still want a good contour map if I were to go wandering into the wilderness. A good map can tell you about the possibilities of the environment, but it's always inferior to looking at it yourself.
  - chmod775 3y ago
    So can obstacles smaller than 50cm. What resolution should we aim for?
    - QuarterReptile 3y ago
      I'm thoroughly nerd-sniped by your username. Is there something special about those permissions?
      - 3y ago

sph 3y ago

> It's crazy to read this, for the same reason that maps used to be military secrets Reminds me of the Map Men episode "Why does Russia have the best maps of Britain?" - https://www.youtube.com/watch?v=_bqzwsM6eoQ https://www.youtube.com/watch?v=_bqzwsM6eoQ