What does decent celestial navigation freeware on Android actually do?

And you _just had_ to cross-post this to sci.electronics.repair ... why?

Yep.

You're unlikely to have a working Android device available in an emergency. At best, a WWV/WWVB receiver, reasonable accurate clock, and HO229 sight reduction tables or this years nautical almanac. If you're going to impress a math teacher, then *YOU* get to do the required math, not the computah. The only thing the computah does is replace the tables and save you from the pain of interpolation. You still have to do 3 other sextant sight corrections (index error, dip, altitude correction). You can download HO229 or the nautical almanac from:

There are plenty of instructional videos on YouTube under "how to use a sextant" and such. Most deal with a noon sight, which is where you start. Since you're likely to be doing this on land, instead of at sea, you'll need an artificial horizon for your sextant.

The rest is RTFM, arithmetic, and practice. Once you've mastered the noon sight, try using the moon or stars. If you want a lesson in reality, find a suitable sailboat, wrap one arm around the mast, and then try taking a series of noon sights.

The free Nautical Almanac. It's in PDF form so you can display it on a laptop, eBook reader, or whatever while you do the math by hand.

Ummm... that it's free? If you want to learn navigation, you're going to need to learn about celestial mechanics, navigational conventions, a fair number of new terms, and what happens when you're in a different part of the planet. You could learn those from a computah program that offers a tutorial, but I believe these are best learned with paper and pen. Once you're proficient with the process, then you can use the computer to allegedly save you some time.

Good luck and have fun.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

You're right Jeff, but one nice thing about knowledge is that you have

*that* always with you, even in an emergency.

So, one goal, always, is to *learn* how to do celestial navigation, where, in a pinch, you can approximate given the experience gained using the battery operated tools.

Really on the accurate clock? C'mon. I'll bet a five-dollar digital watch has better accuracy than all the navigators had in the age of exploration.

Yes. Indeed. But I would like the help of the instruments and the calculations, since, half of math is just intuition on how to do it (which is gained by being right before, when you have more tools available).

Fine with me.

Can a plastic protractor substitute for a sextant for our purposes? (i.e., it's more the process than the accuracy that I'm after.)

Egads. 250 pages. For 2016 only! Another 250 pages for 2017. Plus 180 Megabytes of celestial stuff.

Wow. There's a *lot* of learning that needs to be accomplished. I thought it was just a sighting of about 60 stars!

Ah, Jeff. Thanks for letting me know where you sight. Seems to me a "noon sighting" is easy. stick a twig in the ground, mark when the shadow switches from west to east, and bingo. That's noon at your longitude when compared with GMT, and, voila!

I guess a noon longitude is as simple, using a rough estimate of the angle from the horizon to the sun. Bingo. Latitude.

Interesting. A $32 artificial horizon. Who knew that's needed?

Seems to me a bubble meter should work as well. Right? Can't the phone bubble meter work for an artificial horizon?

Anyway, you are correct these are land sightings. In mountains. Santa Cruz mountains.

Thanks for the suggestion of starting with a noon sight, and then a moon sight (must be a sailor's rhyme there somewhere). And yes, I get seasick, so, I'm intimately familiar with the reality of the motion of the ocean (I give Captain William Bligh a lot of credit for what he done did).

Very interesting that this PDF is all that is needed (along with a sextant and an artificial horizon, both of which should be phone tools if you ask me).

2017: 2016:

For now, Jeff, I'm gonna be at around 35 to 40 degrees North and about 120 to 122 degrees West. After I get good at that, I can work on the other angles.

Thanks for the advice. What would be nice is learning how to do dead reckoning with the phone as the artificial horizon and sextant and a few well-known start (e.g., Polaris) as the frame of reference.

Here are PDF almanacs:

Tools needed should all be on Android for free: a. sextant (tutorial

b. artificial horizon (tutorial c. almanac (tutorial

For example: A. Android Sextant App by Talltree Software:

B. Aircraft Horizon Free by Sensorworks

C. Google Sky Map:

But explorers, by definition, don't need to know exactly where they are because they don't have accurate charts anyway! Not to mention a lot of them came to grief...

Mike.

The early explorers used plenty of charts and tables though!

Peter Hakel has made many spreadsheets for Celnav that are useful.

A perfect Sun sight reduction spreadsheet can be obtained here.

Erik Deman has all of the Nautical Almanac information on his site.

You can get HO 249 Volumes 1, 2 and 3 here;

Fair winds and clear skies.

I'm not sure what manner of emergency would require knowing your exact location using a sextant, but I would guess(tm) that it's either nautical or aeronautical. Somehow, I don't see you tramping around the woods with a sextant. If you're on land, can see some landmarks, and have a map, you don't need a sextant. Therefore, unless you're planning to go sailing or flying, a sextant isn't going to be much help, even with an Android phone (which has a GPS receiver).

Ok, a hybrid approach. I'm more of a purist, but that's fine. As I mumbled, all that an Android app buys you is a laundry list of boxes to fill with numbers, a scratch pad, and if the program is really good, a sanity check.

I'll take the bet. First, you only need an accurate clock if you want to obtain your latitude. Longitude can be done with just a noon sight. Latitude requires a clock.

Find yourself a copy of "Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time" There are also some YouTube videos on the topic of Longitude: (3hrs) (54 min Nova version) There's quite a bit there on how navigation was done in the 18th century including the accuracy of the various John Harrison clocks.

"John Harrison's 'longitude' clock sets new record - 300 years on" One second in 100 days (on land). The target value for an acceptable clock was 1 minute in 50 days.

I don't want to get into a rant on the accuracy of todays digital watches. Everything is dependent on the stability of the tuning for crystal, with is far from temperature stable. I just dug out the specs for a random Casio wristwatch. About +/-12 sec per month at room temp and who knows over a reasonable temperature range. I'm sure someone has done some testing, but I'm late for a free lunch, so you get to Google for the numbers.

No, unless you're only interested in knowing which state you're in. Also, the optics one a sextant are designed to protect your eyes. Prior to the sextant, the use of a cross staff required staring at the sun, a really bad idea.

You're not expected to read it cover to cover. On the average, you'll use 3 or 4 pages at a time. However, for every sighting, all 3 or 4 pages are different.

Stop complaining and start reading.

You can build your own:

Neither is accurate. Bolting a bubble level onto the sextant is that way its done on aeronautical sextants as the sloshing of the liquid in the larger reflection type artificial horizon doesn't work well on a vibrating airplane.

The moon is tricky. It moves quite rapidly across the field of vision and is therefore difficult to get an accurate measurement.

I can tell this is not going to be a classical lesson in navigation. No, you can't borrow any of my sextants.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

On 27 Nov Allodoxaphobia scrit:

Too bad it wasn't cross posted to the windows ng. They could use this information below.

1. TeaCup
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2. StarCalc
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3. SeaClear
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4. Teacup Navigation has free celestial software and a free book in PDF format for downloading. The book teaches the concepts and techniques of celestial navigation, some interesting history, and computational methods using a simple pocket scientific calculator. The book also has condensed tables and work sheets for when you have no calculators available. It also shows how to build your own navigational tools. The free comprehensive celestial navigation software is for the Windows operating system. It will run in Ubuntu (Linux) when "Wine" software is also installed. The same is true for a Mac when the Mac version of Wine is used. The Teacup Navigation site is at
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5. StarCalc is a free program that will bring a planetarium onto your computer monitor. The program is a creation of Alexander E. Zavalishin, a Russian, and is provided at no charge. This program will show a picture of the sky at any time of the day or night from any location in the world at any time. The program provides an alternative to the "Star Finder" plastic circular slide rule used in the JN and N courses. Using the program, you can print a copy of the sky showing the bodies that you intend to "shoot". The graphic provided by StarCalc gives a clear diagram of where the celestial targets of opportunity are located and the hassle of plotting solar system objects is eliminated. The StarCalc program can be downloaded from:
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6. SeaClear is a freeware navigation program for Windows NT 4.0, 2000 or

95/98/ME which, when connected to a GPS (or other unit capable of transmitting NMEA position data), will display the vessel on a chart, with the current position, speed and direction. New charts are loaded as needed. The track may be saved to a file for later reviewing, and log book entries may be manually and automatically entered. An unlimited number of routes and waypoints may be created and used to assist in the navigation. The screen area for charts is maximized with most functions accessed with the right mouse button. Zooming is provided with support for IntelliMouse wheel. The program may be downloaded from:

Sigh. No brain today. That should be Latitude can be done with a noon sight while longitude requires a clock. Dyslexia induced by schlepping a 150 lb drill press up about 40 stairs.

For a common digital clock: "...a typical quartz clock or wristwatch will gain or lose 15 seconds per 30 days (within a normal temperature

second clock drift per day when worn near the body."

or a marine chronometer: "...even in wrist watches such as the Omega Marine Chronometer, that are accurate to within 5 or 20 seconds per year."

Incidentally, be careful what you use for a clock. GPS time is currently 17 seconds ahead of UTC (WWV/WWVB) time: For navigation, you want GMT, UTC or UT1 (all the same). Most GPS receivers and smartphones correct for this, but not every smartphone manufacturer got the memo: Best to check your smartphone: 60 nautical miles = 1 degree of latitude 1 nautical mile = 6076ft 60 NM/sec * 6076ft/NM / 3600 sec/deg= 101 ft/second Therefore the 17 second difference between GMT and UTC will produce an error of about 1,717 ft (about 1/4th nautical mile) in longitude at the equator and lesser errors at higher latitudes.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

You had me scared, Jeff, when you flipped the coordinate system on me.

I'm currently reading this book, so hopefully I'll be slightly more educumated when I next write back. Celestial Navigation in a Teacup, by Rodger E. Farley

The goal is to give the math teacher a lesson for her high school kids, using freeware, where most are on iOS but some are on Android.

My proof reader and copy editor both missed my mistake.

Looks quite good from a quick skim.

The book assumes a working knowledge of geometry and trigonometry which might be suitable for a high skool level class. I think her biggest problem will be adding about 30 navigational terms to the students vocabulary. A navigation glossary might be useful. For example:

Like I suggested. Lose the apps and computah programs initially. Those can come later. Learn navigation with tables, paper, pen, calculator, slide rule, etc. I don't know if they're going to be plotting a course, but plotting sheets might be useful. Once you make it past the geometry and basic concepts, the rest is just math. However, my guess(tm) is that the teacher will become bogged down in the terminology and geometry. Due to lack of time, she will not get very far into practical navigation. At best probably a demonstration.

One problem is getting students a sextant for practice. Even the cheapest plastic sextant (Davis 3) is $50. Make their own sextant, octant, or quadrant? Make sure it has eye protection. I first learned navigation in a class of about 25 aspiring nautical types. Most brought their own sextants of varying quality. We took turns practicing sun sights with everyone using those numbers. I would not expect a high skool student to buy a sextant.

Good luck.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Not many quartz watches qualify as 'chronometers' for navigation purposes. Best practice on ships is to have more than one chronometer on board, and know the 'rate' of each (ie how much it gains or loses each day, usually established by an observatory), and have them wound up and cared for by a designated officer and no-one else. These are used to maintain the accuracy of the watches actually used for observations.

But in an emergency, yes, any reliable watch is better than nothing. As long as the battery doesn't fail.

Consider at least looking at information about the 'astrolabe'; also later developments such as the 'quadrant' and 'back-staff' which preceded the 'sextant', all of which are within the scope of 'handicraft' or 'model-makers' to make (albeit not as accurately as a skilled instrument maker, but a lot cheaper!). I've even used a cardboard astrolabe to get fairly accurate time and latitude measurements. Once you've used an astrolabe, it's easier to grasp what a modern sextant is doing.

As well as maths and so on, this brings in history and culture and geography - and even literature (Chaucer wrote a little treatise on the astrolabe to instruct his son).

Any horizontal reflecting surface will do, eg a lake or strategically placed bowl of water. The nifty gadget is convenient, not essential.

(Astrolabes and quadrants don't need any sort of horizon, they use gravity to establish the vertical plane).

[...]

--
-- ^^^^^^^^^^ 
--  Whiskers  
-- ~~~~~~~~~~

Is trolling again under a different alias.

Please let this one stay a small thread!

Peter Wieck Melrose Park, PA

If it's certified by the COSC, then it's a chronometer: Only a fairly small number of watches are certified.

The specs allow a mechanical clock a daily rate of

-4/+6 sec/day = 2.5 minutes/month = 30 min/year.

However, a crystal controlled clock is only allowed

+/-0.07 sec/day = 2.1 sec/month = 25.2 sec/year.

There are now better clocks that easily meet the COSC requirements:

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

In [possibly] 2008 we bought some Casio 'atomic' watches with solar batteries at Costco for ~$25 each plus tax. The same watches are generally available for >$100 now. Not only are they incredibly accurate due to receiving nightly hits from the atomic clock in [I believe] Boulder CO, the black plastic bands show no sign of wearing out, unlike the bands on previous Casio digital watches I've had.

There's nothing quite like owning a truly accurate timepiece :-)

--
Cheers, Bev 
    "The fact that windows is one of the most popular ways to 
     operate a computer means that evolution has made a general 
     fuckup and our race is doomed."                   -- Anon.

But it is not a "truly accurate timepiece", in the sense that it is not autonomous. It needs a sync signal from outside.

And I hope it is well built... I have a wall clock that syncs every night (about 3 AM) from a radio signal from Germany, I think. The rest of the day it runs autonomously.

However, sometimes there is some problem and it is 15 hours off sync. Depending on the model, it can manage to sync the next day, or never. I can not really trust it.

--
Cheers, Carlos.

I suspect that if Boulder stops sending sync signals the microsecond accuracy of my watch will NOT be on my top-ten problem list :-)

Occasionally it doesn't get an update, probably because I was moving around during the syncing process -- I'm not a good sleeper. Unfortunately, I have no way of judging the resulting inaccuracy.

--
Cheers, Bev 
    "I read about this syndrome called hypochondria in a 
     magazine. I think I've got it."               -- DA

The nightly updates can be a problem. Propagation from WWVB is rather lousy during the daylight hours, and only improves on the left coast around midnight. It's not lack of signal that causes problems. It's interference. It's not uncommon for updates to fail if the watch is left in an RF noisy location, such as next to an operating switching power supply.

Orientation is also a problem. Put the watch down with the tiny loopstick pointed at WWVB and you get no signal even if propagation is good. This is a lousy noisy signal with the end pointed at WWVB: This is what a good signal looks like with the loopstick broadside to WWVB: Even cross polarization will produce a lousy signal. This is a noisy signal with the loopstick oriented vertically:

What the watch does without WWVB updates is a matter of conjecture. I haven't done any testing nor could I find any online. Without the updates from WWVB, it's probably no better than a common digital watch. Even so, that's good enough for navigation, but for accuracy it requires WWVB updates. (4 sec error = 1 nautical mile)

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

I'm surprised that it works. I think you're in Spain and DFC77 transmitter is in Germany. Spain is at the outer edge of the coverage area:

You can improve reception by moving the clock to a location where there is less electrical interference (away from switching power supplies, TV's, computahs, etc). Also, orienting the loopstick so that it is horizontal and "broadside" to the direction of Germany.

That's what happens when the clock receives garbage instead of an update. The usual algorithm is for the clock to receive two or three valid updates in close succession before it will accept the data. If it hears two identical noisy updates, it will display erroneous data. It's very unlikely that this will happen, but it's not impossible. If your clock does NOT require two or three consecutive valid updates, it's highly likely that you will see far more garbage updates.

I don't think a DFC77 clock will work reliably at your location in Spain. Think about using NTP updates from over the internet instead. It can easily be done with a Raspberry Pi. An old handheld GPS receiver, mounted on the wall will also work but watch out for the 17 sec the GPS -> UTC difference.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558