GPS COMPUTER VS SEXTANT/ASTROLABE/Old ways/manual

[SmithDoor]

Interesting reading these posts.

Only partially related, I designed an Astrolabe back in 1993 (on Generic CADD) but it only got to the paper model stage (looks terribly beat up now). It was a PITA because I could not place text on a curve so had to do it letter by letter (or number) and in addition anticipate a vertical offset when the letter was printed. Like I said on my web page at the time I tested it in Canada with one plate and another in St. Lucia (I had plates for every 5deg) and in all cases it was bang-on accurate. What fantastic night skies in St Lucia! I even predicted a solar eclipse and that it would be a grazing partial. I was never able to get photogrametric plates made and lost the source design went I moved on to another job - it was on a work computer back in 1993.
http://surfin_dude.tripod.com/creative/astronomy/astronomy.html#Astrolabe

Previous to that, what got me interested in such things, was a 18” brass sundial design I did which, amongst a host of other things, tracked the sun’s progress across a map on it’s face thought each day and the course of the year. Tricky to etch an 18" dia - 3/8" thick plate or the 1/2" thick gnomen.
http://surfin_dude.tripod.com/creative/astronomy/astronomy.html#Sundial

Now, I keep it simple and use my “Yes V7” watch. Similar but better than the Prague astronomical clock. Used by NASA astronauts & Hollywood movie producers wanting to keep track of daylight. They have a successor to the V7 coming out soon. It will tell you sunrise/set, twilight, moon rise etc a whole host of other things after you program in your city (or manually if your city isn't on the infinitely long list).


No end of fun in this field!

How well dose it work?

Dave

Auto correct on my phone and forgetting to prof read .again

 

[jonpowers]

⫷⸻❋Conclusion❋⸻⫸ ​

.
The old about same century

1. Sextant is 10 minutes within 11 miles on the open ocean
2. Astrolabe is 15 minutes or within 17 miles on the open ocean

*** The Navy using some best today is within 1½ miles or apx 1 minute


Dave

I will comment based on sailing a 24 foot sail boat trans Pacific San Diego via the Pacific Islands to New Zealand: Given the low height of eye, height of waves on horizon and the motion of the sea way I always counted on a 30 (nautical) mile tolerance to produce a cocked hat position fix of Dead Reckoning, morning line of position and noon sight. I always found where I was going. The Polynesians were great travelers judging there position by the eye only estimate of height of celestial objects, based on using basket woven maps, said to be 1/2 degree precision same as I did with a sextant!

Jon

 

[SmithDoor]

I used new technology (home built CNC machine) to engrave this old technology. They look a lot cooler than a GPS chip.

I read about 40 years ago the first navigation tool was simple like astrolabe

I will comment based on sailing a 24 foot sail boat trans Pacific San Diego via the Pacific Islands to New Zealand: Given the low height of eye, height of waves on horizon and the motion of the sea way I always counted on a 30 (nautical) mile tolerance to produce a cocked hat position fix of Dead Reckoning, morning line of position and noon sight. I always found where I was going. The Polynesians were great travelers judging there position by the eye only estimate of height of celestial objects, based on using basket woven maps, said to be 1/2 degree precision same as I did with a sextant!

Jon

Thank you

I was told about same over 50 years but think did I hear that right. So nice hearing again to refresh my memory.
I always remember high noon then dead reckoning till high noon .
I could remember from old western movie everthing happened at high noon.

It nice reading my background is in Aviation and need location almost real time nere mountains. Dead reckoning is used a lot but still needing information faster.

Thank you for sharing
Dave

 

[SmithDoor]

⫷-❋ TIME LINE OF❋-⫸
⫷-❋ NAVIGATION ❋-⫸ ​

The history of navigation dates back to ancient times, with significant developments in various civilizations.

The first part
Celestial navigation, use of landmarks, and early navigational instruments

Celestial Navigation: Ancient navigators used the positions of celestial bodies, such as stars, the sun, and the moon, to determine their position and direction during travel. The North Star (Polaris) was particularly significant in the Northern Hemisphere

Use of Landmarks: Sailors relied on visible landmarks such as mountains, cliffs, and coastlines to orient themselves. When landmarks were absent, they used dead reckoning, calculating their position based on speed, direction, and elapsed time

Early Navigational Instruments: Tools like the astrolabe, a device for measuring the altitude of celestial bodies, and the compass, which provided a way to determine the direction of travel, were crucial for ancient navigation

These techniques and tools enabled ancient sailors to navigate vast oceans and uncharted territories, expanding trade and communication across vast distances

Indo-Pacific Navigation: Began with the Austronesians from Taiwan, who spread southwards into Island Southeast Asia and Island Melanesia around 3000-1000 BC. They used tools like star navigation and wave detection to navigate the Pacific

Greek Navigation: By the third century BC, the Greeks began using the Little Bear (Ursa Minor) to navigate. They also used circumpolar stars to determine latitude


Chinese Compass: In China between 1040 and 1117, the magnetic compass was developed and applied to navigation, allowing sailors to continue their course even when visibility was limited


Portuguese Exploration: In the 16th century, Portuguese explorers took the lead in long-distance oceanic navigation, opening a network of ocean routes covering the Atlantic, Indian, and western Pacific oceans.


Modern Navigation: The invention of the sextant in 1757 and the chronometer in the late 18th century revolutionized navigation, allowing for accurate determination of longitude and latitude.

Open to public after 1983.
The Global Positioning System (GPS) was developed in the 20th century, transforming navigation into a modern technological marvel .
Flight 007 from Alaska to Japan open up GPS.

THE EVENT
(Korean Air Lines Flight 007 (KE007/KAL007)was a scheduled Korean Air Lines flight from New York City to Seoul via Anchorage, Alaska. On September 1, 1983, the flight was shot down by a Soviet Sukhoi Su-15 interceptor aircraft. The Boeing 747 airliner was en route from Anchorage to Seoul) This even that open up GPS TO World

Dave

 

[SmithDoor]

⫷- For longitude -⫸

⫷-It time keeping -⫸

​

• 1642: Galileo proposed an accurate sea clock with a pendulum for a Dutch longitude prize

• 1717: John Harrison completed his first marine chronometer, H1

• 1759: Harrison developed the H4 chronometer, which passed sea trials with flying colors.

Dave

 

[SmithDoor]

In fun picking a time era for building .
Most including myself pick the the era from 1820's to to 1950’s and mostly engines and sundials.

There a hole world full fun ideas for build .
There who build using too of era. I like today's tools.

Myself I am looking at navigation equipment in the1700's this year
Using today's tools and materials keeping simple easy to build.

Dave

testing

 

[SmithDoor]

Here update on design

The PDF Files great details and the other PDF shows different angles

Dave

 

[SmithDoor]

If posting you use with letters to hid the answer or [(ISPOILER]testing[/ISPOILER]
To show how to type I had add a ( remove when using [ISPOILER

White letter hiding
Hight lite between brackets for answer {- TESTING White letter -}
testing ISPOILET

Dave

 

[SmithDoor]

Update on the design. .
The PDF has better details.

Note this has improved filters and mirror. Has a wire for sync horizon to bubble level .
Showes find adjustment

 

[SmithDoor]

Here a link for a good working compass and true north.
I only test on a Android phone.
If someone has apple phone please test anc let us known the outcome

https://www.ngdc.noaa.gov/geomag/calculators/mobileDeclination.shtml#Compass

This shows thf maginic lines for north American

This shows how thd maginic north has moved

World map of maginic lines

 

[ShopShoe]

FYI my iPhones have come with a compass app.

--ShopShoe

 

[SmithDoor]

Detail view of drawing see below for PDF file.
This could be reduced to 4x4 [100mm x 100mm] . It would make it a little harder to build.
I will post a photo tomorrow turn off my computer for knight.

This very helpful if you built a engine for ship 🛳 and need a your location if GPS failed

Show 3 different positions

 

[SmithDoor]

Here is a4x4" [100x100mm ]
The find is gone and everything push closer to gether. With more work it could be down 3" or 3½" [75mm or 88mm]

Dave

 

[SmithDoor]

So......

Further Down the Rabbit Hole....

Amelia Earhart's navigator was using a "Bubble Octant," according to several histories and films made about her disappearance.

Does anyone know anything about that instrument?

--ShopShoe

The best I read and watch on Amelia Earhart's vanishing is her receiver fail.
Navy Radio operator did receiver her message and very strong like she over there ship for time.
Some Navy crew tried to see her aircraft.

After the Japanese pickup her and navigator at this point everthing went cold and more of a guessing game.

The Radio signals was receiver around the world.

Amelia Earhart decided not have a spare Radio and longer antenna so they could carry more fuel.

Sounds like Bubble Octant work great. Just try holding a bubble level on flat ground.

Dave

 

[SmithDoor]

⫷⸻❋ Sextant vs GPS ❋⸻⫸ ​

Part 1 of 2​

.

GPS is the most accurate around 40 inch or 1 meter.

The drawback list. ​

1. Satellite 🛰 and other countries take out
2. Satellite and space debre
3. Sun spots
4. Thunder
5. Power aka battery dead
6. About anything effecting electronics.

⸻⸻⸻⸻⸻⸻
The Sextant ​

While the theoretical maximum accuracy of a celestial fix is 0.1 miles, in reality you will probably never achieve closer than 1 mile.

How Accurate is a Celestial Position Fix?​

The theoretical accuracy of a celestial position fix is based on the accuracy of a sextant. Most sextants let you measure angles to within 0.1 minutes of a degree. 0.1 minutes {6 seconds 0.12 miles 600 feet at equator } on the altitude of a celestial body translates to 0.1 nautical miles on the surface of the earth.

In reality, however, it is almost impossible to actually achieve an accuracy of 0.1 minutes with a sextant.

You are taking your measurements from a moving boat, which is floating on a moving ocean. The horizon needs to be clear, and the celestial body needs to be a perfect, bright speck.

It is far more realistic to get an accuracy of 1 minute with a sextant in day-to-day conditions.

An accuracy of 1 minute with the sextant implies a final position fix accuracy of 1 mile.
With some reading in WW2 the Navey found it 1½ with a good operator most was under 5 miles .

Of course, getting that sort of accuracy relies on minimising every other source of error. Unfortunately, in celestial navigation, there are plenty of potential sources of error: .

1. Errors reading the measurement from the sextant
2. Errors identifying a celestial body
3. Potential inaccuracies in your chronometer
4. Errors in identifying prevailing atmospheric conditions
5. Errors in your calculations
6. Rounding errors
7. Errors plotting the final fix
8. operator holding the sextant

On plus side is

1. no power need
2. No satellites
3. Works with Sun spots
4. Works when electronics does not
5. No power need or batteries

Fortunately though, practise and precision can be used to reduce or eliminate most of these errors.

We can therefore say that an experienced navigator can realistically expect an accuracy of around 1 mile when completing a celestial position fix.

Beginners, on the other hand, will be lucky to achieve an accuracy of 10 miles the majority of the time.

Dave

 

[SmithDoor]

⫷*❋How Accurate does a❋*⫸
⫷*❋Celestial Fix need to be❋*⫸
This also includes GPS ​

Part 2 of 2 ​

Celestial navigation is used when you are far out at sea, when no other methods of position fixing are available.

If you are hundreds of miles from the nearest land, 10 miles of error in your position is not too significant.

Remember, in the middle of an ocean, you will be using a small scale chart. The chart probably covers most of the ocean.

Your position only needs to be accurate enough for you to make landfall in roughly the right place. After that, visual navigational techniques can take over.
Aka {LINE OF SIGHT} easly 10 miles or more.

Dave

 

[SmithDoor]

The next time a very good watch or clock.
Anyone have comments.

Dave





Yes I have take aboutin past and like other view points thank you

 

[SmithDoor]

Interesting reading these posts.

Only partially related, I designed an Astrolabe back in 1993 (on Generic CADD) but it only got to the paper model stage (looks terribly beat up now). It was a PITA because I could not place text on a curve so had to do it letter by letter (or number) and in addition anticipate a vertical offset when the letter was printed. Like I said on my web page at the time I tested it in Canada with one plate and another in St. Lucia (I had plates for every 5deg) and in all cases it was bang-on accurate. What fantastic night skies in St Lucia! I even predicted a solar eclipse and that it would be a grazing partial. I was never able to get photogrametric plates made and lost the source design went I moved on to another job - it was on a work computer back in 1993.
http://surfin_dude.tripod.com/creative/astronomy/astronomy.html#Astrolabe

Previous to that, what got me interested in such things, was a 18” brass sundial design I did which, amongst a host of other things, tracked the sun’s progress across a map on it’s face thought each day and the course of the year. Tricky to etch an 18" dia - 3/8" thick plate or the 1/2" thick gnomen.
http://surfin_dude.tripod.com/creative/astronomy/astronomy.html#Sundial

Now, I keep it simple and use my “Yes V7” watch. Similar but better than the Prague astronomical clock. Used by NASA astronauts & Hollywood movie producers wanting to keep track of daylight. They have a successor to the V7 coming out soon. It will tell you sunrise/set, twilight, moon rise etc a whole host of other things after you program in your city (or manually if your city isn't on the infinitely long list).


No end of fun in this field!

Is it possible of getting photos/drawings of disks used on your Astrolabe.

Dave

 

[Bruno Mueller]

A sextant is still mandatory on modern cargo ships. However, very few ships still have paper charts of the sea areas on board. At most, there are still some from remote ports that do not provide a pilot.
Modern navigation takes place via satellite
The pictures were taken on a trip to Ireland.