[00:00.000 --> 00:00.760]  Excellent.
[00:00.900 --> 00:05.940]  Not as good a time as those that are still asleep, I think, but you're up for the talks and that's the important part.
[00:06.080 --> 00:06.200]  Good.
[00:06.640 --> 00:08.140]  Quick announcement I wanted to make.
[00:08.420 --> 00:13.280]  Five o'clock, there was a sniper forensics talk that has been cancelled.
[00:13.740 --> 00:15.960]  It's actually going to be replaced by the lightning talks.
[00:16.100 --> 00:20.420]  So the lightning talks will be in here at Lovelace at five o'clock tonight.
[00:20.880 --> 00:27.480]  Also want to mention there are amateur radio exams going on now down on the sixth floor.
[00:27.620 --> 00:29.920]  I think these go until about one o'clock.
[00:30.000 --> 00:32.520]  information about them is in the program.
[00:33.580 --> 00:36.600]  So that said, GPS.
[00:36.900 --> 00:37.720]  Some pretty cool stuff.
[00:37.880 --> 00:47.760]  As far as I'm concerned, it's just some magic that tells me where I need to go when I'm staring down at my little screen on my GPS in my car.
[00:47.960 --> 00:50.080]  It turns out there's actually a little bit more to that.
[00:50.660 --> 01:01.460]  And Cass and Ruth here are going to give us some really interesting details in not only how GPS works, but really starting to talk about how to actually interact how to interact with the data that comes out of GPS.
[01:01.720 --> 01:02.180]  Gentlemen.
[01:03.080 --> 01:03.980]  Thank you.
[01:08.000 --> 01:09.800]  My name is Cass Lewart.
[01:09.960 --> 01:11.260]  I'm an electrical engineer.
[01:11.680 --> 01:16.800]  I gave a similar talk at the Trenton Computer Festival a couple of years ago.
[01:17.700 --> 01:20.120]  And then I corresponded with Bernie S.
[01:20.280 --> 01:22.760]  and he made some very nice suggestions.
[01:23.100 --> 01:26.140]  So I modified the talk for this audience.
[01:26.720 --> 01:27.840]  Is Bernie S.
[01:28.000 --> 01:28.880]  here in the audience?
[01:29.860 --> 01:30.840]  Yeah, okay.
[01:31.140 --> 01:33.760]  I think he deserves a round of applause.
[01:38.520 --> 01:41.500]  Okay, you know that this is my business card.
[01:41.920 --> 01:46.660]  I put my coordinates on it so people can find me.
[01:47.320 --> 01:57.440]  By the way, if anybody sends email to the address I'm showing here, rluart.com, I will gladly send you a copy of the view graphs.
[01:57.440 --> 02:03.040]  Just put in the subject line, something like GPS talk or something.
[02:03.300 --> 02:05.240]  So it doesn't go into the trash.
[02:08.080 --> 02:08.600]  Okay.
[02:09.640 --> 02:13.440]  Let me find... I can figure out how this...
[02:14.140 --> 02:14.980]  Let me do it.
[02:15.100 --> 02:17.520]  Don't worry about it.
[02:21.300 --> 02:22.220]  Okay.
[02:23.100 --> 02:26.800]  First, we have a talk outline.
[02:27.100 --> 02:31.860]  I will give you the general specifications of the GPS.
[02:32.400 --> 02:37.860]  I will talk also about the different kinds of GPS units.
[02:38.940 --> 02:55.300]  And one of the important things I want to show you is how your portable unit or the car unit figures out from the clock information from the satellites where you really are.
[02:56.020 --> 03:03.040]  Then we will talk a little bit about GPS for hiking and geocaching and what's in the future.
[03:05.060 --> 03:09.940]  Here's some haiku referring to GPS.
[03:10.220 --> 03:11.460]  I like the last one.
[03:12.140 --> 03:15.620]  You didn't learn how to use the map, how to use the compass.
[03:16.060 --> 03:17.380]  You wait for the rescuers.
[03:21.960 --> 03:23.780]  Now, the basic design.
[03:24.320 --> 03:29.380]  We have the GPS developed by the Department of Defense.
[03:29.740 --> 03:37.660]  We also have the GLONASS developed by the Russian Federation, which was sort of moribund.
[03:37.800 --> 03:39.940]  Now they put some extra satellites.
[03:40.140 --> 03:42.660]  For a while they had like 10, 11 satellites.
[03:42.940 --> 03:44.380]  Now they're up to 21.
[03:44.380 --> 03:52.220]  And as I understand, they gave a receiver with a cell phone to Putin's dog.
[03:52.660 --> 03:55.960]  So they can always locate the dog.
[03:56.820 --> 04:08.780]  However, I don't think there are too many... There are few receivers for GLONASS, but they are not up to American consumer type standards.
[04:08.780 --> 04:16.600]  There's also Galileo system developed by the European Union, which is in development stage.
[04:17.120 --> 04:23.760]  See, one of the problems of GPS is that it's operated by the Department of Defense.
[04:23.760 --> 04:32.380]  And if they ever feel like turning it off, in case of any conflict, then there's no signals that are coming.
[04:35.370 --> 04:42.130]  So, basically, you have 24 satellites in 12-hour orbits.
[04:42.130 --> 04:46.370]  It's about 20,000 kilometers from the Earth.
[04:47.790 --> 04:55.230]  And so, in 12-hour orbit, 24 satellites usually have four or five satellites in view all the time.
[04:55.430 --> 04:57.670]  Sometimes up to six or seven.
[04:58.030 --> 05:03.570]  Depends on where you are and the specific time of the day.
[05:05.550 --> 05:08.390]  This is sort of more or less to scale.
[05:08.390 --> 05:12.030]  You see the Earth and where the satellites are.
[05:13.110 --> 05:14.370]  So, they are about...
[05:14.370 --> 05:17.250]  The Earth's diameter is...
[05:19.210 --> 05:26.950]  About 6,000 kilometers diameter of the Earth.
[05:27.210 --> 05:33.270]  And here we have about 20,000 kilometers at the orbits of the satellites.
[05:34.910 --> 05:40.310]  Here's an artist's rendition of a satellite with Earth in background.
[05:44.720 --> 05:49.300]  Now, these are the main operating modes of the GPS.
[05:49.640 --> 05:57.720]  There's a precise mode used by the Department of Defense and some federal agencies.
[05:59.080 --> 06:03.920]  It's also quite resistant to jamming.
[06:03.920 --> 06:09.980]  The civilian mode used to be very inaccurate.
[06:10.600 --> 06:13.260]  They put sort of a fact factor.
[06:13.340 --> 06:15.680]  It's called selective availability.
[06:17.000 --> 06:23.200]  And President Clinton decided one day to hell with the selective availability.
[06:23.200 --> 06:26.240]  Let's make it useful for everybody.
[06:26.240 --> 06:38.320]  So, the current precision of the civilian system is about the same as of the military system, except it's prone to jamming.
[06:38.640 --> 06:39.340]  So...
[06:39.340 --> 06:41.510]  But in normal...
[06:41.900 --> 06:45.320]  Under normal conditions, it's quite precise.
[06:45.700 --> 06:48.060]  So, you have about 10 meters accuracy.
[06:49.760 --> 07:03.500]  Another two modes are the differential mode and the phase comparison mode used for surveying.
[07:04.160 --> 07:05.080]  On surveying...
[07:05.640 --> 07:12.260]  For surveying, you can get accuracies which go down to centimeters, really.
[07:14.000 --> 07:19.600]  The differential mode was quite popular before this...
[07:19.600 --> 07:21.740]  This fudge factor was removed.
[07:22.380 --> 07:24.420]  Currently, it is of not...
[07:24.420 --> 07:26.680]  That doesn't give you any extra precision.
[07:29.160 --> 07:34.120]  Since a few years, a new mode was added, the WAAS.
[07:35.400 --> 07:38.820]  And practically all new receivers have this capability.
[07:40.140 --> 07:47.520]  There are a couple of geosynchronous satellites, one over the east coast, one over the west coast.
[07:48.400 --> 07:57.960]  To be geosynchronous, in other words, to have an orbit of 24 hours, you need an orbit of about 50,000 kilometers.
[07:58.320 --> 08:04.360]  So, they are considered twice as high as the other 24 satellites.
[08:04.980 --> 08:07.400]  But it gives you some extra precision.
[08:07.560 --> 08:14.200]  There are also some ground stations to which the WAAS system will respond.
[08:19.450 --> 08:28.010]  Now, this is the part which, if you skip the whole talk, this is the most important part of my talk.
[08:28.390 --> 08:31.830]  How you determine the position of the globe.
[08:32.110 --> 08:36.890]  Now, you have extremely precise clocks on the satellites.
[08:37.970 --> 08:45.590]  These are rubidium and cesium clocks, which are within like one second in 300 years.
[08:46.010 --> 08:47.430]  This is the accuracy.
[08:47.670 --> 08:50.470]  In addition, they are being controlled from the ground.
[08:50.710 --> 08:56.550]  So, they are always within a few nanoseconds of the real time.
[08:56.550 --> 09:05.050]  And the satellites send signals, which are received by your GPS unit.
[09:05.430 --> 09:10.230]  And it says, no, it's 11 o'clock, one minute, bing.
[09:11.130 --> 09:13.550]  11 o'clock, two minutes, bing.
[09:14.070 --> 09:20.670]  And in addition to it, the satellites send two other kinds of information.
[09:20.670 --> 09:34.030]  So, one is the clock information, then there's something called ephemeris information, which gives precise location of each satellite at a specific time.
[09:34.310 --> 09:53.670]  So, if you are familiar with astronomy, if you know ephemeris of a star, you know where it rises, when it rises, when it goes down, and where it is at any precise time during its passage on the sky.
[09:54.730 --> 10:00.650]  And in addition, you get almanac information, which gives additional...
[10:00.650 --> 10:10.490]  which tells you if there is... if the clock is not working, or if there's something wrong with your satellite.
[10:10.490 --> 10:16.590]  And this information is received by your GPS unit.
[10:17.270 --> 10:26.410]  So now, let's... to make things simple, I assume there are just two satellites in range.
[10:27.090 --> 10:33.370]  And they are 24,000 kilometers apart.
[10:33.370 --> 10:37.130]  Now, it's 300,000 kilometers per second.
[10:37.370 --> 10:39.370]  This corresponds to 80 milliseconds.
[10:39.370 --> 10:41.010]  Okay?
[10:41.410 --> 10:46.560]  Now, you measure... you check... you compare the clocks...
[10:46.910 --> 10:56.390]  the time signal coming from satellite one, with the signal... with the time signal in your unit, and you find it's 90 milliseconds.
[10:56.990 --> 11:08.990]  You compare the... the clock signal coming from satellite two to your unit, and you find it's... it's 60 milliseconds.
[11:09.790 --> 11:13.190]  So 90 plus 60 is 150, not 80.
[11:13.450 --> 11:15.010]  So what's... what's the reason?
[11:15.150 --> 11:21.930]  The reason is that your local clock is off by... would be...
[11:23.010 --> 11:29.690]  80 minus... it's off by... 35 milliseconds.
[11:30.530 --> 11:37.470]  So if you now subtract from 90, 35 milliseconds, you come with 55.
[11:38.630 --> 11:41.870]  From 60 to 35, you have 25.
[11:41.870 --> 11:53.790]  So if you readjust your local clock by 35 milliseconds, then the distance will be correct.
[11:54.270 --> 11:59.910]  In other words, now you know your clock is... your local clock is readjusted.
[11:59.910 --> 12:10.410]  And now you know that you are 55 times 3, which is 16 and a half thousand kilometers from one satellite.
[12:10.870 --> 12:16.810]  And 25 times 3, 75 hundred kilometers from the other satellite.
[12:16.810 --> 12:20.610]  So you can exactly determine your position on the globe.
[12:20.770 --> 12:22.670]  Now this... I just made it simple.
[12:22.890 --> 12:26.490]  It's a two-dimensional... two-dimensional triangulation.
[12:28.110 --> 12:30.270]  You assume there are three things.
[12:31.190 --> 12:40.630]  And in reality, you need... you need at least four satellites to give you time signals.
[12:41.190 --> 12:54.770]  So from four satellites, you will get both the position on the globe and your height above the... above the sea level.
[12:57.310 --> 13:02.890]  So here I showed those... a repeat of what I was saying.
[13:04.230 --> 13:07.390]  And here's a little picture which shows it.
[13:07.770 --> 13:12.430]  So basically, you get your clock signals from satellites.
[13:13.150 --> 13:15.810]  You know where the satellites are.
[13:15.950 --> 13:18.090]  You know what the satellite's position is.
[13:18.270 --> 13:23.790]  And from this, you can derive how late or fast your local clock is.
[13:23.790 --> 13:25.710]  You adjust this local clock.
[13:25.850 --> 13:34.170]  And now, if you know... you take now the difference between your precise satellite, your precise local clock.
[13:34.550 --> 13:37.910]  Use the 300,000 kilometers per second speed.
[13:38.350 --> 13:42.950]  And you know exactly where you are in relation to the satellites.
[13:42.950 --> 13:50.730]  And the ephemeris information tells you where the satellites are in respect to the Earth.
[13:50.890 --> 13:52.830]  So now you know where you are on the Earth.
[13:53.230 --> 13:58.430]  So this is the basics of the satellite navigation.
[14:01.800 --> 14:04.440]  Now, there are various sources of error.
[14:05.180 --> 14:09.480]  There's noise in the signal coming in.
[14:10.100 --> 14:16.900]  One of the major sources of error is as your signal bounces.
[14:17.260 --> 14:21.120]  These are... there are two frequencies currently being used.
[14:21.120 --> 14:23.600]  It's 1.2 gigahertz and 1.5.
[14:23.820 --> 14:26.900]  One point... it's called L1, L2.
[14:27.160 --> 14:30.460]  So 1.5 is used by the military.
[14:30.820 --> 14:34.180]  You use L1, which is 1.2 gigahertz.
[14:34.440 --> 14:39.580]  So 1.2 gigahertz is about 25 centimeters.
[14:39.580 --> 14:52.540]  So this gives you some feeling how the signal will propagate, how it will be reflected from various... from buildings, from surfaces.
[14:56.630 --> 15:15.150]  And so to know exactly where you are, how the signal connects to you, you have to make a model of the troposphere through which the signal has to pass.
[15:15.310 --> 15:16.870]  And there are some errors in it.
[15:17.870 --> 15:28.350]  In fact, if you do some hiking through the woods, you will see if there is a wood canopy, you may be off by 50 meters, 40, 50 meters.
[15:28.590 --> 15:32.510]  Where in open terrain, you are within 5 to 10 meters.
[15:33.950 --> 15:36.170]  These are the various sources of error.
[15:38.690 --> 15:55.290]  Now, as you can adjust your time signal, your local time signal, extremely accurately through those super precise clocks on the satellites, it can be used for synchronizing networks.
[15:55.950 --> 16:03.910]  And a synchronized network, you may, let's say, open it just for a few milliseconds, pass a signal.
[16:04.130 --> 16:12.050]  So it can be used for cryptography, for passing information at a very specific time.
[16:13.170 --> 16:28.130]  There are various... there are lots of applications for really precise time information, which can be received everywhere on the globe.
[16:31.300 --> 16:33.680]  Now, GPS and relativity.
[16:37.700 --> 16:44.820]  Number one, there's a lower gravity at 20,000 kilometers than the Earth.
[16:44.820 --> 16:54.620]  Also, the clocks are moving, and the satellites are moving quite fast, 12-hour orbit around the Earth.
[16:55.400 --> 16:58.080]  So this affects the time signal.
[16:58.320 --> 17:06.420]  You probably heard, you know, if somebody would go near the speed of light, he would stay eternally young.
[17:06.420 --> 17:19.180]  But these are actually measurable effects, and both the special relativity theory and the general relativity theory affects the clocks.
[17:19.460 --> 17:23.600]  And they actually get adjusted for this effect from the ground.
[17:23.880 --> 17:43.080]  You see, in addition to the satellites, the Department of Defense has a number of stations which communicates with the satellites and basically adjusts the clocks, sends the ephemeris information and almanac information which then relates to the users.
[17:48.420 --> 17:50.340]  And I was showing...
[17:50.340 --> 17:58.480]  There's a document, 48-page document, which I referred to, which is run by...
[17:58.480 --> 18:04.080]  offered by the Department of Defense, which explains exactly what...
[18:04.080 --> 18:07.680]  how the relativity theory affects the time signal.
[18:12.250 --> 18:20.810]  Now, once you get your position, and if you have a sequence of positions, then of course you have speed.
[18:21.770 --> 18:29.690]  Your portable units have all kinds of little computation programs.
[18:29.930 --> 18:30.970]  So you...
[18:30.970 --> 19:00.410]  they will convert your position into latitude and longitude, Into the UTM, if you are doing some work with... where you want to know exactly distances, then UTM is ideal, because both east, west, north, south, each unit is one meter, wherein when you use a second latitude and longitude,
[19:00.410 --> 19:27.690]  because when you go along the longitude, one second is, let's say, one minute is one nautical, one mile on the equator, but it goes to zero near the poles, where the north-south latitude is the same, a second is a second, whether you are near the pole or the equator.
[19:27.690 --> 19:32.230]  But to compute distances, it may get a little complicated.
[19:34.350 --> 19:43.550]  So, once you have two readings of your position, of course, you get speed, you divide the distance by the time.
[19:44.670 --> 20:05.030]  Once you get the speed, you get the position, you can now decide where you are going to, you can get the direction, get heading, bearing, all the information required for navigation by boat, by car, and by a hiker.
[20:09.870 --> 20:15.690]  Now, I will talk quickly about the different types of GPS.
[20:16.050 --> 20:20.270]  You have hand-helds, you have watch units, you can...
[20:20.270 --> 20:28.110]  only in the last couple of years, the car units became quite reasonably priced.
[20:28.310 --> 20:30.170]  It used to be several thousand dollars.
[20:30.390 --> 20:34.090]  Now you can get one for a couple of hundred or less.
[20:38.620 --> 20:45.160]  And then you also have the surveyor types, which are...
[20:46.880 --> 20:52.100]  here you talk about hundreds, now surveyor types, you talk about 10,000.
[20:52.320 --> 21:00.060]  And the military has their own line of GPS units, and God only knows how much do they cost.
[21:00.520 --> 21:05.660]  They use... they built-in cryptography systems, so...
[21:05.660 --> 21:09.480]  So far, I don't know of anybody cracking it.
[21:16.510 --> 21:16.990]  Okay.
[21:17.570 --> 21:21.350]  Now, these are the main features of GPS receivers.
[21:21.690 --> 21:24.150]  They are parallel... they have parallel inputs.
[21:24.330 --> 21:30.030]  You can get 8 to... to 15 satellites at the same time.
[21:33.650 --> 21:46.110]  Some have... you can get... depending on the cost, you have door-to-door communication, you have... you have... you know, staying left, right, etc.
[21:55.320 --> 21:56.480]  Standard... okay.
[21:58.440 --> 22:04.060]  So... there are various... yeah...
[22:04.060 --> 22:11.040]  And then you... to make... you can store waypoints, which means individual points.
[22:11.040 --> 22:13.020]  You can store places where you are.
[22:13.200 --> 22:18.500]  You can store a track where you walked or where you drove.
[22:18.800 --> 22:20.320]  You can recall it.
[22:20.600 --> 22:24.020]  You can... you can build waypoints into routes.
[22:24.280 --> 22:26.160]  So then you have a number of routes.
[22:26.340 --> 22:27.660]  You can recall them.
[22:27.840 --> 22:40.660]  Now, with the memory getting cheaper and cheaper, what... what was quite expensive... impossible to get a few years ago now, and now you get it.
[22:41.200 --> 22:43.880]  You... you get... you get maps.
[22:44.280 --> 22:45.680]  You get base maps.
[22:45.840 --> 22:47.020]  You get detailed maps.
[22:50.320 --> 22:56.100]  And... you... you can... you... you can... change those maps.
[22:56.740 --> 22:57.700]  You can buy them.
[22:58.620 --> 23:00.960]  I will talk about maps later.
[23:01.460 --> 23:05.500]  Now, door-to-door navigation, this became popular in the last couple of years.
[23:05.500 --> 23:12.600]  These are programs where... which... use shortest path algorithms.
[23:13.880 --> 23:17.220]  I worked once on something called Minty algorithm.
[23:17.720 --> 23:26.500]  See, if you want to go from A to B, you can't really do an exhaustive search of... of all possible routes.
[23:26.500 --> 23:36.680]  It would be... even for a simple connection with... in a... city, you would... run into billions of possibilities.
[23:37.160 --> 23:47.380]  So you... you use various algorithms, which... mostly just look at the adjacent path... and select the shortest one.
[23:47.380 --> 23:53.700]  Of course... as... as you will see in a... in a little video I have at the end.
[23:54.080 --> 23:57.780]  It doesn't always lead you... the way you would like to go.
[23:58.520 --> 24:04.420]  So... in other words, if you have your favorite way of going... stick to it.
[24:04.680 --> 24:05.240]  Don't...
[24:05.240 --> 24:13.420]  But if you have no idea how to get from A to B, then... then use... use... door-to-door navigation.
[24:13.420 --> 24:19.100]  Because... these are regular programs running on your GPS.
[24:19.640 --> 24:25.600]  So... they run on the Linux... or on the Windows... mobile platform.
[24:27.160 --> 24:32.100]  You... you can... they are all proprietary programs.
[24:32.620 --> 24:41.400]  So... you... there may be a... group of users which... which cracked the code.
[24:41.400 --> 24:43.960]  And... there's always some kind of trap door.
[24:46.000 --> 24:48.000]  Now... here... here are the various types.
[24:51.100 --> 24:52.380]  Handheld... watch...
[24:53.880 --> 24:55.560]  Mostly... for hiking use.
[24:58.980 --> 25:00.120]  Special... specialized units.
[25:00.420 --> 25:01.900]  Like... my wife uses one.
[25:02.140 --> 25:03.900]  This is for geocaching.
[25:03.960 --> 25:05.880]  I will talk about it a little later.
[25:05.880 --> 25:10.100]  It actually downloads from a geocaching site.
[25:10.260 --> 25:16.280]  To various... various... places where your caches are stored.
[25:17.060 --> 25:21.120]  So it's... so you can do geocaching with any GPS.
[25:21.120 --> 25:26.000]  But this sort of gives you a little edge over the standard unit.
[25:28.080 --> 25:41.100]  And... now... here you have a car unit which... sort of shows the... the picture of the... area... where to make a turn.
[25:41.880 --> 25:44.340]  Inter... intersection, etc.
[25:46.760 --> 25:48.880]  These are military units.
[25:49.760 --> 25:51.400]  Sort of a little bulky.
[25:52.120 --> 25:56.520]  I don't know where... this was... I think a year or two years ago.
[25:56.820 --> 26:00.780]  And... so we're talking about tens of thousands of dollars for each unit.
[26:00.920 --> 26:03.340]  So no wonder in... in many conflicts...
[26:03.340 --> 26:11.240]  the... the... the soldiers are asking your family to send them... civilian units.
[26:11.500 --> 26:15.140]  Which are... certainly more user friendly.
[26:16.800 --> 26:24.260]  Now here are the various... on... on each... GPS you have a number of... screens.
[26:25.340 --> 26:30.400]  And... and you... you... you can... cycle through the various screens.
[26:31.800 --> 26:36.660]  So... this is a... screen which shows you the satellite... coverage.
[26:37.420 --> 26:40.940]  And... you are in the middle and you see those...
[26:40.940 --> 26:40.940]  circles.
[26:41.220 --> 26:47.600]  And you see how many satellites... are visible to the GPS... at... various circles.
[26:49.620 --> 26:55.720]  And... the interesting part is on the third circle... which can still be received by your GPS.
[26:55.720 --> 27:05.040]  The distance to the third circle is... over 5,000... over... over 5,000 miles.
[27:09.310 --> 27:11.390]  This is a compass rose.
[27:11.610 --> 27:17.910]  Another... another... display on your GPS... which... will show you the...
[27:18.470 --> 27:22.210]  If you move... it will show you where the north and south is.
[27:22.210 --> 27:31.710]  Um... some of the units now have also electronic compass... but... a little pain in the neck... because... you... sort of have to...
[27:31.710 --> 27:35.750]  re... reset it once in a while... by walking in a circle.
[27:39.700 --> 27:44.160]  These are... this is another screen... which... you... use quite often.
[27:44.480 --> 27:49.900]  So if you go left... it shows you the distance... to your destination... your speed.
[27:51.120 --> 27:58.500]  Um... when I use it on the plane... shows me the... altitude... and... the time... till... till... you get there.
[28:00.900 --> 28:06.500]  This is another popular... um... display... which is sort of like... three-dimensional.
[28:06.840 --> 28:11.960]  So in this case... you see that... you should go slightly to the left... to get... to your destination.
[28:19.850 --> 28:39.090]  This is another screen... go to... this is a... the other one... which is sort of a... um... um... just... just where you were... little dots... and this is a... more... more... elaborate unit.
[28:39.410 --> 28:47.510]  One... one problem is that... the... the color screen... and the larger unit... requires... also... lots of power.
[28:47.510 --> 28:55.830]  So the smaller units... will run on... on... on two cells... two AA cells... they will run for... um... three... four hours.
[28:55.990 --> 28:59.370]  Where here... you would have to change... your batteries... quite often.
[29:02.280 --> 29:09.160]  This is another popular... screen... you will see... tachometer... tachometer... odometer...
[29:09.160 --> 29:17.600]  So... see where you are... how fast you are going... and the tachometer scale... changes... as your speed increases.
[29:17.600 --> 29:26.900]  So... let's say... if you are on a plane... it will go... to 600 miles... if you walk... it... go from zero... to maybe... uh... 20 miles.
[29:29.160 --> 29:46.790]  This is the time screen... which shows... the local time... possibly... the... uh... UTC time... also... the... um... time... till... till... you arrive... at... your destination... and the... um... time... it took... uh...
[29:46.790 --> 30:02.990]  time... time... how long you traveled... now... the... GPS... every GPS... has... is a... is a... USB... or serial port...
[30:02.990 --> 30:05.350]  a little drink...
[30:18.890 --> 30:19.770]  so...
[30:19.770 --> 30:32.270]  this is how a GPS unit... converses with the PC... now... you... you can use this... port... to update your... your... your software... if you have...
[31:02.010 --> 31:24.770]  And you can find, I have it, the protocol, it's usually like 15, 20 pages, where you have a descriptive, few descriptive characters, you send information to the GPS, and you have a checksum, and then it responds.
[31:25.030 --> 31:27.250]  I will give some examples.
[31:45.120 --> 31:57.260]  So the format of the phrases being sent to the GPS unit and received from the GPS unit is this NMEA.
[31:58.700 --> 32:08.820]  And it starts with a dollar sign, then you have a descriptor, then you have the data unit, then you have an asterisk, and then you have a checksum.
[32:09.940 --> 32:29.900]  If you connect your GPS to, let's say, some kind of terminal emulation, to a terminal emulation program, then you can easily send information to GPS and receive it.
[32:33.680 --> 32:47.680]  However, to be accepted by the GPS, you have to give a checksum, and here I wrote a little program in basic, you can easily translate it to any other language.
[32:47.680 --> 33:05.580]  So it sort of reads your phrase between the dollar sign and the asterisk, and the actual work is done in the next screen in line 70.
[33:05.580 --> 33:24.340]  You XOR each successive ASCII unit, and then once you XOR from left to right, you end up with one byte, so high and low.
[33:24.340 --> 33:34.860]  And you have to send this byte after the asterisk, then the information will be accepted by your GPS.
[33:35.240 --> 33:42.740]  If it's incorrect, then the sentence phrase is rejected.
[33:42.740 --> 33:51.190]  Here is an example.
[33:51.410 --> 34:10.550]  You are sending the top line to your GPS to find the version of your software and to identify your unit.
[34:10.550 --> 34:23.710]  And what comes back, you see below, it gives you the PID, which is product identification, the software identification.
[34:24.250 --> 34:31.850]  Then comes a character string, which is the name of your unit.
[34:31.850 --> 34:43.470]  So if you say you have Magellan, it would say Magellan Sport Track, and then the serial number of your unit.
[34:44.730 --> 34:56.090]  This is important because many software companies now, when they sell you software, they tie it to your specific unit.
[34:56.090 --> 35:05.090]  So if your software receives the wrong serial number, it won't work.
[35:12.010 --> 35:17.810]  Now, usually when you get a GPS unit, it has a built-in base map.
[35:20.250 --> 35:27.250]  When you go to a different area, let's say you go to Europe, this base map will not work.
[35:27.250 --> 35:36.370]  You want to get another base map, the GPS manufacturer will charge you probably more than the GPS unit.
[35:36.590 --> 35:42.230]  So there are various hacks to install base maps on GPS units.
[35:42.850 --> 35:46.930]  And they are definitely unit specific.
[35:47.430 --> 35:54.310]  In other words, what works with Magellan will not work with Garmin, will not work with Lawrence.
[35:54.310 --> 36:06.850]  The way you find out about it, there are news groups, and people just hack their GPSs and find out exactly what to do.
[36:06.850 --> 36:11.490]  I have a Magellan Sport Rack, so you just...
[36:14.250 --> 36:24.470]  You hold the power key and the navigation keys and the power keys, and a little window will open with 00.
[36:24.550 --> 36:31.350]  And now you can change the values in this little window to what you want.
[36:31.350 --> 36:39.430]  So I wrote instructions, actually, how to install a base map on your Magellan GPS.
[36:41.490 --> 36:51.910]  Whenever the manufacturer like Magellan finds somewhere the base maps posted, they try to remove them.
[36:56.040 --> 36:57.700]  One word of caution.
[36:58.180 --> 36:58.340]  One word of caution.
[36:58.340 --> 37:00.340]  You have to know what you are doing.
[37:00.480 --> 37:07.580]  Because if you put a wrong number into that little window, you may completely disable your unit.
[37:08.660 --> 37:11.760]  But many times you can recover from it.
[37:17.670 --> 37:20.290]  Now, GPSs are great for hiking.
[37:24.870 --> 37:27.210]  You know where you want to go.
[37:27.450 --> 37:28.590]  You follow a trail.
[37:31.530 --> 37:34.410]  It will tell you when to turn, left or right.
[37:36.350 --> 37:40.230]  You have to keep track of something called heading and something called bearing.
[37:40.450 --> 37:43.850]  Heading is the direction in which you are going.
[37:43.850 --> 37:47.070]  I mean, north would be heading of zero.
[37:47.430 --> 37:49.490]  South would be heading of 180.
[37:50.210 --> 37:55.030]  And bearing is the angle to your destination.
[37:55.110 --> 38:02.550]  So if you are traveling directly to your destination, the bearing would be zero.
[38:02.910 --> 38:07.330]  If you have to go to the right, the bearing would be maybe 20 degrees.
[38:07.330 --> 38:14.050]  So if you know what's heading, what's bearing, you will get there.
[38:14.190 --> 38:21.730]  Some of the units also tell you whether to turn left or right by a specific number of degrees.
[38:26.010 --> 38:26.950]  How are we doing?
[38:28.270 --> 38:28.990]  50.
[38:29.850 --> 38:30.290]  Okay.
[38:30.790 --> 38:32.470]  Now here I connect.
[38:32.770 --> 38:35.910]  We made a hike in Huber Woods.
[38:36.790 --> 38:38.610]  It's in Manmouth County.
[38:39.630 --> 38:41.070]  New Jersey.
[38:41.630 --> 38:49.010]  And the GPS keeps, records the track, how you walked.
[38:49.330 --> 38:51.970]  So you can then transfer.
[38:52.210 --> 38:54.090]  There are many software programs.
[38:54.370 --> 38:58.090]  Here I use Topo USA from DeLorme.
[38:58.150 --> 39:07.330]  And you can transfer your track to your PC, which has the Topo maps.
[39:07.330 --> 39:11.910]  And then you can see exactly how you walk, how you hike.
[39:12.130 --> 39:13.930]  So this is a great thing.
[39:14.070 --> 39:21.210]  You connect your GPS to your computer where you install, let's say, Topo USA or many other programs.
[39:21.610 --> 39:25.870]  And you can study your route.
[39:29.980 --> 39:40.700]  Now, the built-in compass, the compass reading from your, on your GPS requires that you move.
[39:40.980 --> 39:48.520]  Because, you know, the satellite doesn't know which way is north or south.
[39:48.520 --> 39:51.240]  Now it tells you your position, your speed.
[39:51.480 --> 39:57.040]  But to get an idea where there's, if you stand still, then there's no speed.
[39:57.220 --> 40:02.600]  And you don't, you won't know where the north or south, where north or south is.
[40:02.600 --> 40:05.200]  So a compass is helpful.
[40:05.520 --> 40:08.440]  Now here I show a very nice compass.
[40:08.840 --> 40:13.500]  I had one, it was stolen from me, then I ordered one from Germany.
[40:13.960 --> 40:18.140]  And this type of compass costs around 100, 150 dollars.
[40:18.480 --> 40:23.720]  But it's a compass which is good to within one or two degrees.
[40:27.300 --> 40:31.520]  And you can, it has a little prism in the viewer.
[40:31.940 --> 40:36.740]  So you can look at the, at your destination as you turn your compass.
[40:37.120 --> 40:45.120]  And at the same time you can read the compass rows on the, on the compass to within one or two degrees.
[40:45.900 --> 40:50.000]  If you can afford it, this compass is fantastic.
[40:50.000 --> 40:57.080]  I, I prefer it much more to electronic compasses, which I don't trust.
[40:57.640 --> 41:05.360]  And also an electronic compass can really, if you do something wrong, it will really mislead you.
[41:05.880 --> 41:07.820]  When magnetic compass will not.
[41:08.140 --> 41:13.740]  One of the features of this compass, it's quite heavy, it's made with brass.
[41:13.740 --> 41:19.320]  So it, it kills all the, uh, local eddy currents.
[41:19.720 --> 41:31.120]  Uh, I can use it on a plane and, uh, it, it isn't affected by the, uh, by the induction from, from the various fields.
[41:36.680 --> 41:39.840]  Now, a few words about geocaching.
[41:39.840 --> 41:41.500]  It's a worldwide sport.
[41:42.500 --> 41:44.160]  And they have their site.
[41:45.040 --> 41:46.080]  It's free.
[41:46.460 --> 41:48.720]  You want, uh, special privileges.
[41:48.980 --> 41:51.430]  They pay maybe fifteen, twenty-five dollars a year.
[41:52.410 --> 41:57.460]  It gives you locations or little caches all over the world.
[41:58.100 --> 42:00.180]  It's all on public ground.
[42:00.180 --> 42:03.800]  So in parks, in recreation areas.
[42:05.100 --> 42:12.840]  Um, and you, you will find either, you, you get a location and you, you go to that place.
[42:13.080 --> 42:19.900]  You, you look around, you will usually find a little box with some, some, uh, knickknacks inside.
[42:19.900 --> 42:29.300]  So you may take something, you put something in, and then you log on, you log, um, on the web that you discovered it.
[42:29.300 --> 42:36.040]  So, uh, Ruth and I, uh, are currently up to about 120 of those caches.
[42:36.460 --> 42:46.660]  One of the big things, if you do geocaching, is that you discover areas in your own backyard you were never aware they existed.
[42:46.950 --> 42:57.040]  I mean, beautiful nature preserve areas which are so hidden until you discover them through, through one of those posts.
[42:57.040 --> 43:05.000]  Just every week there are new posts showing the, um, the new caches in your area.
[43:06.540 --> 43:13.060]  Here we are in Minnesota, uh, family and friends doing some geocaching.
[43:13.950 --> 43:19.450]  Both, uh, this is a sport which both the kids and the adults enjoy it.
[43:21.600 --> 43:25.930]  Here is one cache we found in New Jersey, you see, in a tree trunk.
[43:26.640 --> 43:28.240]  And there's a box.
[43:29.020 --> 43:30.880]  I mean, this is a large box.
[43:31.380 --> 43:33.800]  Uh, the frequencies are ammo boxes.
[43:34.100 --> 43:42.920]  But you can also find, uh, some of those, uh, caches are just, you know, maybe one centimeter across.
[43:42.920 --> 43:45.480]  And maybe hanging on a tree.
[43:46.640 --> 43:58.660]  Also, sometimes you have, um, you have hints which, um, like we went to, um, to watch a reservation in, in, uh, Union County in New Jersey.
[43:58.660 --> 44:03.560]  And we had three locations, three sides of a triangle.
[44:04.200 --> 44:12.640]  And now you had to draw, uh, find the center of the circumscribed circle.
[44:12.860 --> 44:16.780]  And the center of it was, was, uh, was our cache.
[44:17.000 --> 44:18.980]  So you have to do some computation.
[44:19.380 --> 44:22.140]  Because you can't work with latitude, longitude.
[44:22.140 --> 44:24.380]  You have to convert to UTMs.
[44:24.440 --> 44:27.780]  And you, you do with UTM and find your caches.
[44:31.480 --> 44:34.460]  Uh, GPS on a commercial flight.
[44:34.720 --> 44:36.120]  This was my experience.
[44:36.300 --> 44:40.500]  I always keep it, it's a good test how good your GPS is.
[44:40.720 --> 44:44.500]  If you hold it against the window, does it catch enough satellites?
[44:44.500 --> 44:52.600]  So you know where you are, how far to go, how, how fast you are going, uh, your altitude, everything.
[44:54.140 --> 45:03.760]  And, uh, my experience was that, uh, the stewardess, I was holding this, and the stewardess told me to put it away.
[45:04.220 --> 45:06.800]  I put it away when the stewardess went.
[45:06.960 --> 45:09.820]  I put it against the window again.
[45:10.240 --> 45:13.060]  And then she noticed it.
[45:13.300 --> 45:15.460]  She said, well, I will report to the captain.
[45:15.700 --> 45:17.420]  I said, well, what can I do?
[45:17.700 --> 45:23.740]  And she comes back, the captain said, if you warn us if we are going off course, you can use it.
[45:27.220 --> 45:38.600]  Uh, there's also, uh, you can also find out if, uh, if officially they allow you to use it as a site.
[45:38.600 --> 45:42.760]  Uh, what, what, what's the, what are the various airlines policies.
[45:43.420 --> 45:48.000]  Uh, in general, they let you use it if you are above 10,000 feet.
[45:48.540 --> 45:51.700]  Uh, same thing with the cell phones.
[45:56.010 --> 45:58.990]  Now, GPS on, GPS on the web.
[45:59.210 --> 46:00.430]  These are various sites.
[46:01.310 --> 46:04.270]  Um, there's also some trade magnet.
[46:04.490 --> 46:10.550]  If you have access to USENET, which is become more and more difficult to get to.
[46:10.850 --> 46:16.350]  There's a good geocaching, um, um, site on USENET.
[46:16.350 --> 46:19.790]  And, uh, the manufacturer keeps their posts.
[46:20.010 --> 46:31.550]  And there's some general geocaching, uh, I mean, general, um, GPS sites, where you can find reviews of various units.
[46:32.390 --> 46:33.350]  There's all this...
[46:33.350 --> 46:33.770]  A good time.
[46:34.070 --> 46:34.390]  Yeah.
[46:34.650 --> 46:35.710]  I still have a few minutes.
[46:37.950 --> 46:38.550]  Yeah.
[46:38.550 --> 46:44.450]  Uh, there are also some, uh, um, some trade magazines you may subscribe to.
[46:45.150 --> 46:47.910]  Um, okay.
[46:49.130 --> 46:52.230]  These are the various ways they, they operate.
[46:52.510 --> 46:57.870]  I mean, the power supplies, uh, rechargeable cells.
[46:58.310 --> 47:06.090]  Um, the manufacturer, of course, tried to convince you to subscribe to some service and pay and pay and pay.
[47:10.390 --> 47:18.550]  So these are the current trends to make a subscription instead of, uh, one-time purchase.
[47:19.550 --> 47:26.570]  And, uh, also to use, uh, batteries, which, uh, can be replaced.
[47:27.370 --> 47:30.030]  Um, where do you go from here?
[47:30.590 --> 47:34.930]  This, uh, most of the current satellites reach their design limit.
[47:34.930 --> 47:40.910]  So there is, uh, um, the new ones will have, uh, will have higher powers.
[47:41.110 --> 47:43.150]  It's called BLOCK-3 satellites.
[47:44.050 --> 47:46.310]  Now, at the end, I would like to show you...
[47:46.310 --> 47:48.310]  This is the last end of my slideshow.
[47:48.390 --> 47:48.770]  I would...
[47:48.770 --> 47:49.810]  I would...
[47:49.810 --> 47:55.930]  I have a little, uh, little, uh, cartoon from Simpsons.
[47:55.930 --> 47:58.390]  I would like to show it to you.
[47:58.750 --> 47:59.350]  Okay,
[48:10.830 --> 48:11.130]  okay.
[48:11.530 --> 48:13.250]  This will show you that...
[48:13.250 --> 48:15.110]  will show you that...
[48:15.110 --> 48:19.110]  you can't always rely on the door-to-door navigation.
[48:20.430 --> 48:23.310]  This is the NEM data document.
[48:24.490 --> 48:24.950]  Um...
[48:24.950 --> 48:27.150]  Yeah, and this is just an example.
[48:27.590 --> 48:27.790]  Yeah.
[48:28.550 --> 48:29.940]  Now, let's go to Simpsons.
[48:30.670 --> 48:31.430]  Yeah, I'm trying.
[48:47.490 --> 48:47.950]  Hmm...
[48:47.950 --> 48:49.030]  Let's see if it matches.
[48:56.590 --> 48:57.270]  Heh heh.
[48:57.690 --> 49:01.250]  Thanks to our new GPS, I'll have you at school in no time.
[49:01.730 --> 49:02.210]  Heh heh heh.
[49:02.210 --> 49:04.930]  Turn right in 50 meters.
[49:05.190 --> 49:06.370]  Oh, meters!
[49:06.850 --> 49:11.010]  Dad, a meter is three inches longer than a yard, which is 36 inches.
[49:11.310 --> 49:14.570]  So, 50 divided by 39 times 36 equals...
[49:14.570 --> 49:15.850]  You have missed your turn.
[49:16.450 --> 49:17.050]  Recalculating.
[49:17.270 --> 49:19.690]  Turn right in .5 meters.
[49:20.010 --> 49:20.710]  Dad, no!
[49:20.870 --> 49:22.570]  That takes us into a construction site!
[49:22.690 --> 49:25.230]  Stupid kid thinks he's smarter than a computer.
[49:27.370 --> 49:28.270]  Seatbelts, kids!
[49:33.530 --> 49:34.630]  Turn left.
[49:34.850 --> 49:35.410]  Turn right.
[49:35.650 --> 49:36.270]  Turn left.
[49:36.510 --> 49:36.990]  Turn right.
[49:44.820 --> 49:46.780]  Decrease elevation 10 feet.
[49:46.980 --> 49:47.800]  Then turn left.
[49:48.040 --> 49:48.600]  Don't!
[49:49.740 --> 49:51.600]  You have reached your destination.
[49:52.980 --> 49:54.300]  Thanks for the ride!
[49:54.320 --> 49:54.580]  Bye, Dad!
[49:55.200 --> 49:57.860]  Turn right in 2.3 kilometers.
[49:59.040 --> 49:59.720]  Recalculating.
[50:00.260 --> 50:01.380]  So cold.
[50:01.720 --> 50:02.520]  So cold.
[50:05.460 --> 50:07.060]  Okay, this is it.
[50:11.650 --> 50:14.950]  There's a little audio synchronization problem.
[50:15.390 --> 50:24.390]  So, the reason he throws it into the water is that she has given him the distance in kilometers, which blows his mind, so he throws it in the water.
[50:25.750 --> 50:26.230]  Right.
[50:26.490 --> 50:29.190]  If you have any questions, go ahead.
[50:34.920 --> 50:36.600]  Maybe we turn the lights on.
[50:36.820 --> 50:36.980]  Yeah.
[50:37.960 --> 50:38.020]  Yeah.
[50:38.520 --> 50:40.980]  How is Galileo going to change anything?
[50:41.100 --> 50:44.060]  Is that going to be different from GPS, the European Galileo system?
[50:45.040 --> 50:49.280]  Well, as I understand, it's still in the planning stage.
[50:49.560 --> 50:50.540]  So, until...
[50:51.060 --> 50:52.820]  I think they saw...
[50:52.820 --> 50:55.060]  They shot a couple of...
[50:56.100 --> 51:00.420]  Just for testing, I think they shot one unit up.
[51:00.600 --> 51:02.260]  But I'm not sure whether...
[51:02.260 --> 51:03.960]  I doubt they would be compatible.
[51:03.960 --> 51:09.600]  So, probably you would need a different set of receivers.
[51:09.960 --> 51:11.260]  Same thing with GLONASS.
[51:11.800 --> 51:12.820]  It's not compatible.
[51:13.460 --> 51:18.880]  GLONASS uses elliptical orbits rather than circular orbits.
[51:18.880 --> 51:23.680]  So that the Russian satellites are more...
[51:23.680 --> 51:33.260]  Spend more time over the Russian federations than the rest of the world.
[51:39.340 --> 51:40.060]  Hello.
[51:40.400 --> 51:46.320]  I'd like to know what company makes that German compass with the brass housing and where to order it.
[51:47.360 --> 51:48.860]  Okay, it's K...
[51:49.840 --> 51:52.860]  If you send me email, I will try to find it.
[51:53.000 --> 51:55.560]  It took me quite a lot of searching.
[51:55.900 --> 51:57.560]  It's a fantastic compass.
[51:57.900 --> 51:59.060]  It's K&E.
[52:00.680 --> 52:01.980]  They took it...
[52:01.980 --> 52:07.300]  In fact, I ordered it by phone and they said they don't accept any credit cards.
[52:08.000 --> 52:15.020]  So I put $100 in an envelope and send it to Germany and it worked.
[52:15.680 --> 52:18.200]  Thank you.
[52:18.280 --> 52:21.620]  But it's probably more than you need for geocaching.
[52:21.840 --> 52:23.640]  It's great for hiking.
[52:23.980 --> 52:26.020]  It's a fantastic compass.
[52:26.400 --> 52:27.980]  It would be good enough for surveying.
[52:27.980 --> 52:28.640]  Yeah.
[52:29.340 --> 52:29.860]  Nearly.
[52:30.760 --> 52:35.460]  Because it has a bubble, so you know, you can...
[52:35.980 --> 52:38.820]  It has a way you can put it on a tripod.
[52:39.340 --> 52:41.840]  So it's a really nice unit.
[52:41.840 --> 52:46.460]  The GPS is used for military and civilian.
[52:46.720 --> 52:49.060]  And so it's obviously subject to being...
[52:49.060 --> 52:50.340]  It's being...
[52:50.340 --> 52:53.840]  It's subject to being destroyed or tampered with or injured.
[52:54.660 --> 52:59.080]  And also, it's also subject to radiation, solar flares and that sort of thing.
[52:59.220 --> 53:01.860]  So if that happens, aren't we too reliant on GPS?
[53:02.020 --> 53:06.100]  If it's being used everywhere and we're all pinned on GPS, shouldn't...
[53:06.100 --> 53:08.860]  Don't you think that's sort of a dangerous situation?
[53:08.860 --> 53:14.860]  Well, the DOD sort of does the civilian...
[53:15.880 --> 53:18.820]  It gives them a favor.
[53:19.480 --> 53:24.620]  So they don't promise anything that they will keep it going or whatever.
[53:25.200 --> 53:31.940]  So that's the reason why the European Union is trying to develop their own unit.
[53:32.480 --> 53:42.880]  The GPS is basically a military gadget and it's used on missiles, used for artillery purposes.
[53:43.860 --> 53:50.680]  And as a sideline, they give it to the civilian population and use it the way you want it.
[53:54.390 --> 53:58.450]  So they give you no promises that they will keep it going.
[53:59.290 --> 54:00.510]  All right, I have a quick question.
[54:00.510 --> 54:04.110]  Is there any error generation from atmospheric distortions?
[54:04.210 --> 54:11.810]  Like if you have a storm, like say in a hurricane or what not, is there going to be more error being generated within the devices?
[54:16.430 --> 54:26.010]  I guess, well, in a storm you will get slight distortion, but I didn't notice anything.
[54:26.010 --> 54:37.630]  It's more in the woods and the leaf canopy will affect your reception much more than a storm.
[54:38.530 --> 54:41.070]  I don't really mean the reception.
[54:41.330 --> 54:59.870]  I was thinking that the signal coming in from the GPS satellite from space down to Earth, I was curious if any kind of like storm or crazy atmospheric phenomena might, I guess you could say bend it or affect it or some way that would otherwise mess with your GPS.
[55:00.170 --> 55:05.270]  Well, it may, but you always receive like at least four or five satellites.
[55:06.350 --> 55:08.270]  I guess we have to, yeah.
[55:09.590 --> 55:11.310]  I guess it looks like we are finished.
[55:12.290 --> 55:12.950]  Quick one.
[55:13.870 --> 55:14.610]  How is this?
[55:15.970 --> 55:18.890]  If you want to have any questions, I will be outside.
[55:20.750 --> 55:21.410]  Thank you.