How Far Can You See a Light? Assuming the Earth is not Flat....

[@MarinaMatic]

After being a lead instructor at maritime university for 15 years I can not believe the time has come where I have to start my lecture with 1-hour evidence of Earth is not flat. makes me wanna have a t-shirt of Capt. Pikard facepalming.

[@salvitoripopadillo4539]

Could you give us some of your evidence that you start your lecture with?

[@SageTrader007]

Too bad all evidence proves it's flat. Just like lighthouses. Sorry.

[@Ryanm229]

Happy to see your videos are coming back and like the sneaky image changes.

[@NavigationTraining]

Thank you Ryan!

[@galiceanudan-adrian5804]

We missed you, sir! 😄

[@sailingaphrodite4189]

Well said sir.

[@NavigationTraining]

Thank you! My sailing schedule is all over the place with the world situation, but I am shooting for one video per month this year, February is done and will come out Monday. Have a good day!

[@kiwiboys]

Very informative. I’m currently sailing 57 NM south of Singapore and can see a vague glow coming from that direction. I doubt it’s the city but can’t be sure. It is a fairly clear night after all.

[@siddharthchaudhary7753]

Lots of ships are at anchor ⚓ in hat area, even the sea/ Singapore🇸🇬 strait is surrounded by islands and mainlands.!

[@salvitoripopadillo4539]

You are certainly seeing Way further than you should be considering that your on a sphere/(oblate or whatever) with a circumference of 24,901 miles!!! At only ten miles there would have to be approximately 66 feet of curve between you and an object only Ten miles away.

[@marcg1686]

​@@salvitoripopadillo4539 Do you understand the difference glow and points of light?

[@Worldofchavo]

Fantastic easy explanation

[@Seafarer.]

Very great explanation,this explanation in wonderful and so good and complete and also short but covers this topic conpletely to be used in chart work subject calculations and in real situation for plotting and using on charts

[@montithered4741]

One thing to consider, the geographic range is actually the GEOMETRIC range because the calculations include many assumptions which apply only to geometry, not reality. Assumptions commonly applied include, but aren’t limited to: 1 - The earth is a perfectly smooth sphere 2 - The earth has no atmosphere 3 - Points 1 & 2 shouldn’t need to be explained yet people constantly forget these things 4 - line of sight distance is equal to the ground arc distance 5 - height of viewer is near zero for intermediate calculation steps. 6 - no atmospheric refraction 7 - assume radius from center of the earth to the surface at the viewing point and object point are equal; see point 1 8 - if atmospheric refraction is included, the air is assumed to be dry, standard atmosphere All those conditions never happen. As a result, the calculated visibility is often SHORTER than the actual visibility.

[@karhukivi]

The nominal range is a function of the luminosity of the light and a "standard" atmospheric visibility. It takes no account of the curvature of the earth - just a straight-line path in a 74% visibility. It has to be corrected if the actual visibility is different from the 10nm "standard" value. The geometric range is a function of the observer height and the light elevation and is a straight line over the curvature of the earth. If this is shorter than the corrected nominal range, then the light can be seen, as the light is capable of being seen at a greater distance, given an observer high enough. Under certain conditions, refraction can allow the light to be seen at a greater distance.

[@789train]

thank you for great video, i learned something. let me help you, there is a word for vertically challenged, it's shorter and takes less letters! lol

[@bidmunk2000]

Bravo!

[@michella1913]

Hello, thank you for the interesting topic. Does the formula for the Geographic Range displayed at 2:00 take into account the refraction of light due to the atmospheric layers?

[@NavigationTraining]

Hello! No you can get some weird light effects, but this formula is based just on the size of the planet and the height of the light for a geographic range in nautical miles. Same ducting effect can happen with radar and give you a huge radar range too. Good point!

[@michella1913]

@@NavigationTraining Thank you! I didn't know it also happened with radar.

[@CNV49]

THANKS

[@NavigationTraining]

You're welcome!

[@jerrytugable]

Good explanation, also applies to VHF and radar.

[@NavigationTraining]

Totally, good point!

[@CaptMarkSVAlcina]

@@NavigationTraining can you explain on your next video how this applies to VHF and Radar , thanks

[@NavigationTraining]

Sure thing both radar and VHF (including AIS) are based on line-of-sight, so the same formula will give you distance that those electronics could be assumed to reach. In practice you can have a higher or sometimes lesser range based on factors like sea and atmosphere conditions too.

[@justincase5124]

I live in Melbourne Australia. From Altona beach we can see across Port Phillip Bay which is 60 kilometers away. During the day you can see the land (highest land is 51 meters) and during the night you can see the lights of whatever is there! Around 250meters of curve should prevent me from seeing this

[@marcg1686]

Altona Beach ->Arthurs Seat Lookout = 55km. Arthurs Seat Lookout is situated more than 300 metres above sea level.

[@kirenireves]

I'm taking ASA 105 by correspondence and the chart's visibility distances for lights confuses me. Why would they list the visibility as 25M when the geo distance is only 15M? For example, Brenton Reef Light (off of Newport, RI; in Rhode Island Sound) is listed at 87 ft with a 25M visibility. But at 87 ft you only get visibility of around 11M (Bowditch T-12). Even if you add an observer at the standard 15 ft over the water, it only adds 4.5M or so. Total 15-16M. So why does the chart say 25M visibility? Seems like a physical impossibility. Is that visibility in a straight line? Like if you were in a helicopter 25M away hovering at 87 ft (observer at 87 ft) you'd just barely see it? Is that how the nominal distance works? Is "nominal distance" just another way to say lumens or brightness of a light? Help!

[@karhukivi]

The nominal range is indeed linked to the luminosity of the light as it is assumed we don't know the height of the observer. Also, it is luminosity corrected (by international agreement) for an "average" atmosphere" with a transparency of 74% or 10 nm. So you take your nominal range of 25M and use the chart to obtain the actual range for the weather conditions of visibility for the area, let's say it is 10M visibility so the actual range is the same as the nominal range = 25M. Now you apply your light elevation and observer height to the geometric distance formula and you get say 14M. The light has a range of 25M and you have a geometric distance of 14M so you will see it. If the local visibility was only 2M the chart would show the light range to be only 7M and you are at a distance of 14M, so you won't see it. The nominal range shown on the chart is effectively the candlepower of the light but shown as a distance in nm for an "average" visibility of 74%. I hope all that makes sense - good luck!

[@salvitoripopadillo4539]

Does Lake Superior have curve to it? Can you measure the curve of that lake?

[@richn811]

Nope! You can’t now what’s that tell you..?

[@karhukivi]

When canals and railroads were being constructed, the surveyors using optical levels had to apply corrections for curvature and refraction otherwise the canals would drain away. These tables can be found in any surveying book and are continuous proof that the earth is not flat! If you surveyed along the shore of the lake and didn't apply corrections for curvature, you would find that your "level" was becoming progressively higher than the lake level. Level is not flat, a billiard table is flat but if I put a book under one leg it will still be flat but not level.

[@salvitoripopadillo4539]

@@karhukivi Absolutely not. You are incorrect! Go out and use your own eyes. Get a telescope, high zoom camera, try mirror flashes or Whatever. There is no observable, measurable curve! Surveyors do Not account for curvature. At only ten miles, you'd have approximately 66 feet of curve. Standing on either side of Lake Millacs (approximately 10 miles across) you will clearly see the shore of the other side in the summer, day or night and in the winter when it's frozen! There are Thousands of other cases of people all around the plane that have observed the lack of curvature at much greater distances than only ten miles!

[@FlatzoidsPerspective]

You do know raising your elevation is just widening the angle and this you see more. Aka flat surface. There is no such thing as physical curve. And just to point out you did not work out curve lol

[@robertlafleur5179]

@@marcg1686Foolzoid never learns anything. He repeats the same idiocies as all other flerfs.

[@SageTrader007]

Good thing the Earth is Flat otherwise lighthouses wouldn't work!

[@donluca1824]

Light houses prove the earth is flat

[@NavigationTraining]

Thanks Don, how is that exactly? Just curious your thought process. Thanks!

[@marcg1686]

@@NavigationTraining He doesn't have thought processes. He's a flattard, he just smears whatever comes out of his mind's ringpiece across the comments section. I'm sorry that channels like yours have have to put up with this mindless flat earth crap. Hoping to see another 'soup to nuts' complete sight reduction from you. 🙂

[@jholyroller6048]

EARTH IS FLAT BIBLE SAYS CLEARLY GOD'S WORD YOU CANT SEPARATE AN CHOOSE WHAT U WANT YO ITS GODS WORD NOT YOURS GOD SAYS NOT TO ADD OR SUBTRACT FROM HIS HOLY WORD AN THIS IS what they. Do globe earthers

[@marcg1686]

Whatever...

[@IveOdyssey]

I am a daughter of God, His gentile and it is very blasphemous to say that the earth is flat. Where does in The Holy Bible-Scriptures says that? God Haves everything under His Control, He have things under His Plan and it is programed that the plant earth is round. Continents and the oceans are too big to be placed on one solid flat surface therefore it needed to be spread which it makes things logical that the earth is round to hold all that is around the earth none like flat. If it were flat, it wouldn't have capacity to hold everything in it, if it were that way, the flat earth will be destroyed because it wouldn't have gravitational force and yet it wouldn't hold what's on it. If the earth was flat, then why in the world the sun would shine to the other side of the planet if there's nothing to shine if it is rotate. It will be crazy if the world be flat because we will all have the same time zones. It doesn't makes sense as to say the planet earth is flat. We have to obey God's Creation because He is The Law of Physics. It is deep visually and spiritually.