Hi Guys, A newbie here and hope all is well with you guys.
I am an Electrical Engineer and I live in Pennsylvania.
For religious purposes, our place of worship needs to know the direction to the following GPS coordinates: 31?ø46?ý40.7??N 35?ø14?ý8.9??E ( The place is located in Jerusalem, Israel and we are supposed to be facing in that direction while praying)
Yes, we have a rough idea which way Jerusalem is, but I am interested in finding the exact direction to Jerusalem from our city.
My city's coordinates are 40.7 latitude and -73.9 longitude.
When I typed my city's coordinates into the following website, I was told that the azimuth between my city and Jerusalem was 54 degrees, 4 minutes and 11 seconds.
The website is https://keisan.casio.com/
Now here is where I need your expertise.
Does the info given by the website mean that, if I take a compass and place it on a table, Jerusalem will be exactly in the direction of 54 degrees, 4 minutes and 11 seconds from my city?
Is it that simple? Do I have to do other math with the Azimuth info?
Thank you for your replies.
You also need to know the current magnetic declination at your location.?ÿ The magnetic pole is not the same as the geographic pole. For that lat/lon and this year I get 12.75?ø W using this lookup.
https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#declination
That means the compass points west of the geographic north.
12?ø 45'
54?ø 04'
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66?ø 49' = 66.8?ø compass reading New York to Jerusalem
?ÿ
Here's an iOS app called the Mizrach Compass that helps locate Kodesh Hakodashim in Jerusalem.?ÿ Looks pretty straight forward.?ÿ There's a video on the link below:
https://www.rustybrick.com/iphone-mizrach.php
Thank you so much for your answer. Let me confirm this again. If I had the most reliable magnetic compass money can buy, then the direction where 66.8 degrees is pointing on that compass will be the direction to Jerusalem, correct?
Are there any other geographic/ mathematical corrections after this that are supposed to be made? Or is this the more or less final step in the calculation? Ty again!
rhumb line or great circle ?
If you went due east from your location you would end up north of your destination so I would find the answer to Jim Cox's question before making that determination.
Unsure of the answer to your question. Need to ask around. Ty
I would think great circle, which the above numbers represent. That way you are always heading for the shortest path to the destination. The compass heading along that path is not constant. That's the path a radio wave would follow.
Rhumb (loxodrome) maintains a constant heading, but does not follow the shortest path.
If you maintained a constant heading east (constant latitude), yes you go north of the target.
But the great circle, shortest path, goes to higher latitudes near the start and then lower latitudes near the destination. Stretch a string on a globe to illustrate it.
IF (that's a big if) the custom of facing toward a certain city began before it was discovered and generally accepted that the world was round, then the great circle would not apply. (my opinion only)
If the custom began when the world was thought to be flat, then treat it like drawing a line on a flat map.
http://www.levin.rutgers.edu/research/geography-paper.pdf
this is discussed a bit here...apparently there is at least one mosque which faces NE in the US to point towards Mecca...
Thank you for your feedback. You have a very good point. We always held that the earth was a sphere.So, yes, I am looking for a "sphere" solution to my original question. Ty
Judaism wouldn't have thought the world was flat, would it? And certainly the fairly new religion of Islam would have the benefit of the the Greeks and know that the world was round?
Just because a few people in the middle ages may have thought the earth was flat doesn't mean that most rational people have ever thought so.
"If the custom began when the world was thought to be flat, then treat it like drawing a line on a flat map."
Ah, but which map projection? And sufficiently accurate maps to make a difference probably did not exist before knowledge that the earth was round.
Barring any theological information to the contrary, I would think facing the direction that had the shortest distance would apply.
It would be interesting to try an experiment if you have access to a recreational grade GPS. Simply store a way point and go in and edit it to the coordinates you stated in your post. Then outside hit 'Go To' and I'm curious if it will give you an azimuth and distance to Jerusalem. No magnetic declination involved. You could mark a point outside of your place of worship and then go out a distance and circle that point until you arrive at the same azimuth that you started with and mark that point and you now have a line pointing in the direction you're seeking. Compare that to what other means you use to determine the direction and see how well they compare. If the two points are far enough apart they should be fairly close to the true geodetic azimuth. Given the accuracy of the GPS is in the order of 15'+/-, the farther apart the two are, the closer they will be. Maybe do it several times for an average??ÿ
Just because I'm paranoid, doesn't mean they aren't out to get me.
Recreational GPS units typically do a decent approximation to the great circle route.
But in your method any place within blocks will give you nearly the same azimuth to the destination waypoint so that won't help.
When you go walking around, you need a waypoint to that starting point, and look for the reverse azimuth (add or subtract 180?ø) of the actual destination. The fact that the starting point is probably inside a building is another difficulty
I believe everyone is describing a direction as it relates to the curved surface of the earth. But if, as you say, you want the exact direction to Jerusalem you would need to combine the azimuth with a particular downward facing angle towards the ground so that you would indeed be facing Jerusalem and not just finding a surface route to get there, but a straight line that would go through the earth directly to Jerusalem.
Good point. Suppose I hadn't really thought that one through.
Just because I'm paranoid, doesn't mean they aren't out to get me.
Ladies and gents. Thank you very much for all the info. You all have been fabulous. It will take some time for me to do the experiments that some of you proposed. I will be in touch. There is a holiday around the corner, but I hope to be in touch in a few weeks.
Thank you all again!
BTW, there is some research out there on this:
http://www.levin.rutgers.edu/research/geography-paper.pdf
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