 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 you know 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 draw you some graphics. So I'm going to try going out here to open CPN 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 as a sailboat looks like it's about to come in punts 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 that 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 fold 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 spooks their AIS latitude longitude of a vessel and they try to let's say knock Louisiana off the air and now they spoof being Louisiana well there 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 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 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 seven 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 one two or three 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 that 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 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 gonna have the course in degrees zero degrees being true north and so an actual course will be somewhere between zero and 359 the speed and knots a knot of course is a nautical mile per hour which translates to about 1.15 miles per hour I'm gonna 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 match the reality life would be a good thing but here for is actually an example and and 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 B's as well so technically speaking if you're a class A vessel at your anchor you just need to transmit every three minutes now you may be saying but I'm an 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 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 zero and 14 knots I'm supposed to be transmitting every 10 seconds if I am sailing at a speed of zero 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 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 we'll look at I've got I've got a ship here that's supposed to be a ship and is it some latitude and longitude which I'm calling lat zero and long zero I know my course overground 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 tea time later on I've got my new latitude 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 overground and the rate of turn I can figure out the distance that I've traveled that that circular distance that the 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 overground 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 do north or do anything it'd be easy but as we start to change off of zero degrees we start to see you know some complications because again a degree of latitude is the same everywhere in terms of linear length but the linear length of a 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 my 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 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 before 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 then 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 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's here's a table 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 and that actually you know makes sense until of course you get to the pole and then a degree of longitude is zero nautical miles and again I'd give me 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 start to go from there I like I said I talked to read 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 half to see 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 the sea village so I'll sit here for a couple minutes while we go into Q&A