Okay, folks, I think we are back. Let me try once again sharing my screen.
And once again, I'm going to live dangerously and show the whole thing.
So, when we were talking about ideas for talks and projects and things like that,
one of the things that I just happened to mention, and somebody said, well, this seems like it'd be
an interesting little challenge type of project to do. And I'm going to talk to you about something
called AIS point prediction. So, here's the general idea. And if I was better at drawing
graphics, I could have drawn you some graphics. So, I'm going to try going out here to OpenCPN
to see what kind of things we've got going out here. What I really need, and I probably don't
have, well, actually, I probably do have, but you see these vessels out here. This vessel right here,
the Janus, we know is a sailboat. It looks like it's about to come in Ponce Inlet. The Sea King,
I don't know anything about the Sea King. It's also a Type B. That's too bad, but that's okay.
On AIS messages, vessels that are by Code of Federal Regulations required to transmit Class A
type of vessels. So, the really big ones have a lot of passengers, have a certain tonnage or
horsepower. They're Class A. And a Class A is going to be telling me all the information that's
down here. They'll be telling me a speed, course, heading, and turn rate. They'll also be communicating
relatively frequently. Class B vessels, the smaller ones,
aren't required to transmit. And in fact, in a Class B position report, there's no way to even
tell me about a turn rate. So, the reason I'm telling you that is so that I can tell you this.
My question is, and here's an example of Louisiana, which was just offshore pretty
recently, a tanker, offshore Daytona. So, if I know a ship's latitude, longitude,
speed over ground, course over ground, and turn rate, can I predict where they will be
the next time they give me a position report? And in some ways, this sounds like a trivial exercise.
I fooled around a little bit with it, not a lot. It's a really interesting exercise.
And the idea came to me some time ago, the idea being, you know, I'm at a particular place.
And suppose a bad guy spoofs their AIS latitude, longitude of a vessel. And they try to, let's say,
knock Louisiana off the air. And now they spoof, bing, Louisiana. Well,
suppose their next position report puts me five miles away. Well, there's no way that I can move
five miles in a minute. So, my AIS receiver could maybe flash red to say, we just got something that
just doesn't seem right. Now, the other thing, by the way, that this AIS message will tell us,
this position message, this and other things, is you'll notice that this is also giving me
the destination and ETA of when I plan on getting there. So, this vessel, which I saw the other day,
probably about four or five days ago, is expected tomorrow morning at 7 in the morning UTC to be
in Texas. So, it must have, well, it must have been several days ago. Anyway, so where I'm going with
this is this. Again, an AIS type 1, 2, or 3 message is a class A position report. And the information
that matters to me is it's going to give me a latitude. For those of you that are not familiar
with the relationship between latitude, longitude, and distance, it is vaguely as follows. One degree
of latitude is 60 nautical miles. One minute of latitude is one nautical mile. Longitude is about,
one degree of longitude is about 60 nautical miles at the equator, which is zero degrees latitude,
of course. But for every other, any other latitude, a degree of longitude, the linear distance
is going to be some function of the latitude. And think about a globe. And, of course, as you get
closer and closer to the North Pole, one degree of longitude gets to be almost nothing, whereas
one degree of longitude at the equator is 60 nautical miles. Anyway, I mentioned that later on.
Then we're going to have the course in degrees, zero degrees being true north. And so an actual
course will be somewhere between zero and 359. The speed in knots. A knot, of course, is a nautical
mile per hour, which translates to about 1.15 miles per hour. I'm going to have a rate of turn,
which is generally expressed in the number of degrees per minute, left or right. And the time
between transmission is going to be a function of what is your speed and what is your rate of turn.
And it turns out there's a standard for this, and if only the standard matched the reality,
life would be a good thing. But here is actually an example, and it talks about some of the
additional issues related to the problem. So I only care about the Class A transponder types,
although I'm showing you Class Bs as well. So technically speaking, if you're a Class A vessel,
you're at anchor, you just need to transmit every three minutes. Now, you may be saying,
but I'm at anchor, I'm not moving. Well, again, AIS Class A devices, you might be talking about
a vessel that is several hundred meters in length. If it's anchored or moored, the position
of the bridge might be actually composing a circle, that if that ship were to swing around
its anchor in a 360-degree circle, you might be talking about a radius of many hundreds of meters.
Well, a nautical mile is about 2,000 yards, so I might, like I said, I might have a pretty big
swing radius. In any case, if I'm sailing, not sailing obviously, but underway between 0 and 14
knots, I'm supposed to be transmitting every 10 seconds. If I am sailing at a speed of 0 to 14
knots and changing course, I need to be transmitting every 3.33 seconds. So that's how you read the
chart in terms of transmission rate. What I did is I then translated this and said, well, what's the
maximum distance I can travel in that amount of time? Well, if I'm going 14 knots and I'm transmitting
every 10 seconds, I'm only going to be traveling 77 yards. That's not very far. And you can sort of
see as my, as I progressed here, what I was trying to give was an idea of exactly how far might I be
going between transmissions. Now, I mentioned I wish the reality were, you know, match the standard.
Sometimes we will see vessels going by that are class A vessels and they're pretty big class A
vessels. And like the Louisiana, the Louisiana was going at 15 knots. Well, at 15 knots, even in a
straight line, they should be transmitting every six seconds. But we had like a minute, that slide
that I showed. So in any case, you know, so the distance or rather the rate between transmissions
is something else we need to take into account. So then I said, well, okay, I've got, I've got a
ship here. That's supposed to be a ship. And it's at some latitude and longitude, which I'm calling
lat zero and long zero. I know my course over ground. I know my rate of turn. And so the question
is, all right, well, I've got a triangle in here. I've got some angle theta. Now, this may or may
not be the right approach to go, by the way, but I've got some angle theta. And so at some t time
later on, I've got my new latitude and longitude, lat one and long one. And so I will observe that
I can figure out the radius of this circle because it's going to be related to the speed over ground
and the rate of turn. I can figure out the distance that I've traveled, that circular
distance, that arc, if you will. That's going to be somehow related to the velocity times the time
between the transmissions, the actual time. And then I've got this delta x and delta y.
Well, delta x is going to be a function of the angle of the circle, the speed over ground and
the time, which as will my delta y. But then my actual change in latitude and longitude
has got to be a function of the course plus theta, meaning that if I was just going due north
or do anything, it'd be easy. But as we start to change off of zero degrees, we start to see,
because again, a degree of latitude is the same everywhere in terms of linear length,
but the linear length of the degree of longitude is not going to be the same.
So like I said, we have, you know, that issue to deal with. So again, my targets that I'm going for
is if there's no rotation of the ship and the ship is moving in a straight line, well, that's
almost easy to do. If the rate of turn is not zero, my ship is turning. And so then the other
thing I was thinking of is not only can I, how well can I predict my next point, but, you know,
we just had a tropical storm down here last week, went up the east coast. And so we always look at
the National Hurricane Center and they give us this cone of certainty for, so that if my next
point is in the box, do I claim victory? And am I looking for, well, a really small box or how big
will I let my box be? If I'm going in a straight line, they really are sort of boxes. If my rate
of turn isn't zero, then the boxes actually become a cone. Am I anywhere in the right range at all?
So, like I said, in terms of a problem, I was just thinking that this sounds like an
interesting problem to tinker with. And, and there's all sorts of places to look at historical
information. What you need to work on, though, if you get historical information, and I could even
provide you some, is you need type one, type two, or type three position reports from the same vessel.
And, and the type one, again, because you need rate of turn. Now, I mentioned something about
the length of the degree of latitude and longitude. So, again, the length of the degree of latitude
in meters, there's, there's a formula that I know is used at a number of the government sites.
It was actually easy to find the formula because they have these pages where they have like a
JavaScript, and you can, you know, put in, you know, what your latitude is. It will tell you the
length of a degree of latitude in meters. Well, of course, if you right-click and look at the
page source, you can see their formula. But it's been used a lot, and I've seen it documented in
a few places. In any case, the length of the degree of longitude, again, you will also notice
is a function of the latitude. The length of the degree of latitude and longitude, here, here's,
that I produced largely from those formulas. And you will notice that a degree of latitude,
in terms of nautical miles, it almost doesn't matter where you are. It's about 60 miles,
60 nautical miles to a degree. If you look at a degree of longitude, the number of nautical miles,
again, at the equator, it's about 60. And then, as you go towards the poles, it increasingly gets
smaller and smaller, and then rapidly gets smaller once you get above about, you know, 45 degrees,
either north or south. And that actually, you know, makes sense. Until, of course,
you get to the pole, and then the degree of longitude is zero nautical miles.
And again, I've given you some websites where they have more information about this.
And that, more or less, was the challenge. And as I said, I think it's sort of an interesting
problem. And for a few people, I don't know where we sort of go from there. I, like I said, I talked
to Reid out about this, and I think he talked to a couple of other people. Interesting problem.
I think what we're looking for is maybe to have some intermediaries, intermediate solutions at
some point in the next year, maybe revisit this at Hack to C 3.0 next year. And anyway,
so that's where I am. So, questions? Comments? Let me go back up here. I'm no longer
at Hack to C Village. So, I'll sit here for a couple minutes while we go into Q&A.