• Saik0
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    12 days ago

    No, you need 4 minimum.

    Two satellites intersection places you on a circle. (all points possible)

    Three satellites intersection places you on two possible points.

    The last satellite give you the exact location.

    However, the 4th can be omitted if one of the 2 points is not in a sane location. (eg well below the crust). And it’s trilateration not triangulation.

    The reality is that your phone/device will use like a dozen satellites.

    • SaltySalamander
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      111 days ago

      three sats determine your accurate position. the fourth is for clock correction only.

      • Saik0
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        211 days ago

        No.

        Satellites project a sphere, you need 4 in order to get to a singular point. I’ve outlined each step. Fourth isn’t for clock correction only. And even outlined why sometimes 3 is okay, but that requires additional logic that many gps devices sometimes can’t compute, and even outlined that the vast majority of devices will use way more than 4.

        https://gisgeography.com/trilateration-triangulation-gps/
        https://www.gps.gov/multimedia/tutorials/trilateration/

          • Saik0
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            11 days ago

            Deleted your comment because you looked at the last image?

            Edit: The images on the site depict the exact thing I’ve been referencing.

            1 satellite = whole sphere of options.
            2 satellites = a whole circle of options
            3 = 2 points
            4 = 1 point.

    • Ulrich
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      -412 days ago

      Uhhh nope, that’s incorrect.

      The way triangulation works is by essentially measuring distance.

      So 1 satellite distance puts you anywhere in a radius (circle) of that satellite.

      2 Satellites puts you at 1 of 2 locations where those radiuses intersect.

      3 satellites gives you a single location.

      That’s why it’s called triangulation. Tri = 3

      • @notfromhere@lemmy.ml
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        912 days ago

        Oh boy, where do I even start? This comment is wrong in multiple ways. Let’s break it down:

        1. “The way triangulation works is by essentially measuring distance.”

          • Nope. This describes trilateration, not triangulation.
          • Triangulation uses angles, while trilateration uses distances. GPS works via trilateration.
        2. “1 satellite distance puts you anywhere in a radius (circle) of that satellite.”

          • Kind of, but missing a crucial detail:
            • A single satellite defines a sphere around itself (not just a circle—you exist in 3D space).
        3. “2 Satellites puts you at 1 of 2 locations where those radiuses intersect.”

          • Wrong. Two satellite distance spheres intersect to form a circle, not just two points.
        4. “3 satellites gives you a single location.”

          • Mostly right, but incomplete.
          • In theory, three satellites narrow it down to two possible points, but one is often out in space or somewhere unrealistic, so it can often be ruled out.
          • However, because your device lacks an atomic clock, it typically requires four satellites to synchronize time properly.
        5. “That’s why it’s called triangulation. Tri = 3”

          • Nope. GPS does NOT use triangulation.
          • The “tri” in triangulation comes from angles, not the number of satellites. GPS uses trilateration, which is based on measuring distances, not angles.

        Final Verdict

        This comment is a trainwreck of incorrect terms and flawed explanations. If they meant “trilateration,” at least part of it would make sense, but calling it “triangulation” completely ruins their credibility.

        So, in short? No, their comment is very incorrect. 🚨

        • Ulrich
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          12 days ago

          A single satellite defines a sphere around itself (not just a circle—you exist in 3D space).

          You are not getting a 3 dimensional location. That’s why GPS coordinates only exist on 2 planes. You don’t know what you’re talking about.

          Final Verdict

          You’re not just wrong, you’re wrong AND you’re a dick about it.

          • Saik0
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            12 days ago

            You are not getting a 3 dimensional location. That’s why GPS coordinates only exist on 2 planes. You don’t know what you’re talking about.

            Coordinates on a sphere is a 3 dimensional location. The earth isn’t flat.

            Edit: Please education yourself before you’re so confident in your own bullshit answer. https://gisgeography.com/trilateration-triangulation-gps/ and https://www.gps.gov/multimedia/tutorials/trilateration/

            Satellites broadcast a sphere, not a circle. And that sphere doesn’t land on the earth as a perfect circle for relatively obvious reason… since the ground isn’t perfect flat, nor is the earth perfectly spheroid.

            • Ulrich
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              -212 days ago

              The earth isn’t flat.

              So which coordinate accounts for elevation? Latitude or Longitude?

              • Saik0
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                311 days ago

                Lat/Long is only valid if elevation is valid. You can’t reference a lat/long that is miles into space… or beneath the crust of the earth.

                • Ulrich
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                  -111 days ago

                  It’s like you’re making my point for me.

                  • Saik0
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                    211 days ago

                    A watch… or other simple gps device doesn’t know what the elevation is.

                    Only one of the 2 selected points in a 3 satellite setup will be valid. And your device would have no idea which one is valid without elevation knowledge or a 4th satellite. Some devices can figure it out with just 3 satellites. Many/most won’t. But ultimately it’s the same thing. You need 4 pieces of input. Either 3 satellites AND elevation. Or 4 satellites.

                    So no. I’ve not made a point “for” you. You’re just ignorant or specifically being obtuse on something you clearly don’t understand.