Like, why wouldn’t people be interested in knowing that the African slave trade of the colonial period actually started with Jewish kids, but they all died in the African climate of Sao Tome, so the Portuguese started buying slaves from the Congolese, which they captured from neighboring tribes, to work the fields??

  • starman2112@sh.itjust.worksEnglish
    12·
    1 year ago

    I wrote about it on that other website a couple years ago, I’ll link to archives of my posts there

    Here’s what I submitted to the Subnautica forum

    Here’s what I submitted to the Tasker forum

    Tasker is an Android application that lets you automate many different things. One of its features is setting variables for use in your tasks–for example, I have a task sets the variable %Wallpaper to a random number between 1 and 152, and sets my phone wallpaper to DCIM/Backgrounds/%Wallpaper.png every time I turn on my screen, because I don’t want to stay married to one specific wallpaper

    You can also do math with variables, which allowed me to program the trilateration algorithm on this webpage into Tasker. All you need to input is your current depth, and your distance to each of three specific landmarks (oceanmarks?), and it’ll do all the complicated squaring and adding and subtracting for you, and then give you a notification with your approximate coordinates–in testing, it’s usually accurate to within about 10 meters, which is more than accurate enough for us to see whatever we’re looking for.

    I wish I could actually understand why the squaring and adding and subtracting gives you accurate coordinates, but you don’t got to know what baking powder does to make good bread, you just gotta follow the recipe!

    • Ms. ArmoredThirteenEnglish
      2·
      1 year ago

      You’ve got me curious about this now too lol. I work with games and love this kind of thing. I’ll know more once I’m not trying to do research on a phone, but the squaring part looks like just a distance formula (A^2 + B^2 = C^2). My very rough guess with the subtracting and adding is you’re basically doing vector math but I’m unsure. I can respond or edit later as I find out more.

    • joonazan@discuss.tchncs.deEnglish
      2·
      1 year ago

      It represents each circle as an equation that is only true when x and y are on the circle. By requiring that all three equations are true, you can find all points that are on all three circles.

      You can either convince yourself that three circles can only intersect at one point or you can use the fact that two variables and three independent equations means that there are zero or one solutions that satisfy all equations.

      You could actually even make a system that only needs two distances (and the depth)! Two circles can only intersect at two points, so you just need to figure out which one of the two you are. That can be done by looking at which of the landmarks is on the left when looking towards them.

      Now the really difficult thing here is to figure out why this works even with inaccurate inputs, as the math presented on the site assumes that everything is perfectly accurate.

      You can actually formulate different ways of computing the position that differ in how they react to measurement error. One way to investigate that is to take the derivative wrt. to one of the radii.

      This resonated with me because I once did the same thing but in 3d and with magnetic field strength instead of distance. I never found a satisfying solution because magnetic fields are capsule-shaped rather that spherical. The shape is described by a 4th degree equation, so its exact solution is too large to be useful and the whole system of equations cannot be solved symbolically.

      I hope that didn’t get too intimidating.