calculater for degree/minutes/seconds to digital degrees

[tadd5181]

I found a calculator for changing degree/minutes/seconds to digital degrees , but I'd like a formula or directions for doing it myself rather that using the calculator. Any help is appreciated.

The site for the calculator is found at compassdude.com under longitude/latitude if you want that.

 

[Brian D]

If I think you are asking for this, then this is how I do it.

25° 25' 25"
25" / 60 = .4166'
25' + .4166' = 25.4166'
25.4166' / 60 = .42361°
25° + .42361° = 25.42361°

Reverse the process
25.42361° - 25° = .42361°
.42361° * 60 = 25.4166'
25.4166' - 25' = .4166'
.4166' * 60 = 25" (actually 24.996")
25° 25' 25"

 

[Allan12210]

My RPN calculator (HP 12C or phone app) does it with a single button.

25° 25' 25" is entered 25.2525 (hh.mmss). Then press --》H button to get 25.42361111 (hh.hhhhhhhh). To reverse enter the decimal degrees and press f then --》HMS.

 

[BigEasy]

Allan,
What phone app are you using?

 

[JamesG161]

25° 25' 25" is entered 25.2525 (hh.mmss).

How about 25° 25' 25.25" in the app?
@Brian D would be 25.25" / 60 = 0.4208 to convert seconds to minutes.
Jim...

PS: You are converting seconds to minute (60) and then minutes to degrees (also 60)

 

[Allan12210]

Allan,
What phone app are you using?

Big Easy,

I have an Android phone and am using the RpnCalc - Rpn Calculator app. It works the same as my HP calculators I've always used.

Allan

 

[Allan12210]

How about 25° 25' 25.25" in the app?
@Brian D would be 25.25" / 60 = 0.4208 to convert seconds to minutes.
Jim...

PS: You are converting seconds to minute (60) and then minutes to degrees (also 60)

James,
The app works the same way. Just enter 25.252525 (hh.mmssss) and you get the same answer as if you did it the way Brian D has shown us. That is 25.423681 (hh.hhhhhh) degrees. The phone app treats hours just like degrees. 60 minutes per hour or 60 minutes per degree.

Allan

 

[Brian D]

@JamesG161, where are you 25.25"? Do we need to deal that close to include tenths and hundredths of a second? Just round up/down to the nearest integer of seconds. The OP's question was how to manually convert DMS to decimal degrees. I am assuming he does not have a Reverse Polish Notation calculator but might be carrying a very simple calculator if anything at all.

 

[JamesG161]

@JamesG161, where are you 25.25"?

My point was the USCG uses 39 degrees decimal 23456 in their calls (example). They use it for accuracy. I hear four to five places.
And my GPS/chartplotter does the same.

If your GPS is good to ±10 feet. Just what is that in Seconds?
Jim...

 

[Brian D]

Two decimal places calculate about 2nm. Three decimal places out to about .4 nm. I would say at least three decimal places would be accurate enough. If one has a GPS then this whole subject is moot. And if one is contacting the USCG using paper charts, then the USCG can do the calculation, hence, this subject is moot. But I think the OP just wants to learn how to do the math which is OK with me. A little knowledge can be useful some day, like Algebra... might just save your life. LOL

10 ft might be six decimal places?

 

[JamesG161]

If one has a GPS then this whole subject is moot.

Well "Beauty is the Eye of the Beholder"

I asked a question about the extra points and @Allan12210 gave me the answer.

The other reason for 39.12345 is to rapidly compute distance from the new wreck located at 38.22357 and thus the distance between the two points is...

(38.22357 - 39.12345) * 60 ≈ 54 nautical miles away

and revert it back to 38° mm' ssss" to find it on a paper chart and mark it there.

Each to his own needs.
Jim...

 

[Brian D]

It's all good.

 

[Bill Roosa]

Look at your chart and try to tell the difference between 24 and 25 seconds of arc. Unless you have a very small scale (zoomed way in) chart the smallest increment will be minutes. I'm thinking that you could guesstimate 0, 15, 30, and 45 seconds but not much else. If memory serves one second of arc at the earth's surface is about 6'
All you really need for chart navigation is minutes. FWIW

 

[dziedzicmj]

1 minute is 1 nm. This means that 1 second is 1852 m / 60 = ~ 30 m or about 100 ft.

 

[Newport Bob]

1 minute is 1 nm. This means that 1 second is 1852 m / 60 = ~ 30 m or about 100 ft.

Only true for latitude

 

[JamesG161]

I had forgotten that Hours/Degrees were same thing in a conversion of minutes and seconds.
@Allan12210 Thanks!

I have to admit my Raymarine Chart plotter does ALL the calculations from NOAA charts and has the option or Long/Lat or Decimal degrees.

I also admit that the Line Officer Star on my shoulder board was earned by knowing and doing hand/chart and celestial navigation.

I also admit I found this brand new set left aboard by the previous owners. Still in its sealed OEM wrapper.
http://www.weems-plath.com/Website-...ets/Professional-Mariners-Navigation-Kit.html
which allows precision beyond your eyes.

I also admit that I own a precision HP 800 printer that prints NOAA charts to any scale I want 36" x 24".
http://www.charts.noaa.gov/PDFs/PDFs.shtml

I also admit I only use the paper charts for pinpointing good fishing spots so my buddies and I can roll out a chart at table sipping beer and fantasize/planning trips. This is really where I would use that APP.

I am only commenting about this to show what might go through an individual's mind when responding to a thread. Perhaps I like different things, I have different needs, enjoy remembering how things used to be done, or most importantly....

Be prepared when the Zombies take over the GPS sat systems!


Take Care...
Jim...

PS: If you are passing by me, I will print a NOAA precision, color chart, to your scale for free.
Well maybe a beer.

 

[Stu Jackson]

Only true for latitude

Not really.

 

[Kings Gambit]

Not really.

I think what we have to say here is: "One minute of latitude equals one nautical mile on a Mecator projection." If you're going to measure a distance between two points on a Mecator chart, one needs to use the latitude scale in the same area of the chart where the measurement is taking place. For example, if you wished to mark off the distance from the Golden Gate to one of the Farallon islands, one would use the latitude scale around 38 deg North rather than the one, for example, around 32 deg North, etc., as I'm sure you--Stu--well know.

 

[JamesG161]

Not really.

1 minute is 1 nm. This means that 1 second is 1852 m / 60 = ~ 30 m or about 100 ft.

Well you both are right.
Perhaps most are not used to the "approximately equals character" short version of "~" or "≈"

@Kings Gambit is right on target!

Here is what is right too.
https://en.wikipedia.org/wiki/Nautical_mile

Jim...

 

[Chevy1217]

Great Thread I learned a Lot from it Thank You Gave me a Refresher Coarse in Trig. and Most Confuse NM with Statute Mile A statute mile is 1609.34 meters and the Nautical Mile is 1852 meters but get confused because they usually fig it using Yard's. and not meters they use the standard 1760 yard instead and are confused between the Meter Standard I know I do 1.15 is a Good Value to Remember the Difference between NM and SM and is used because on arc minute measured along any meridian. It is equal to the length of one arc minute along the equator. And a nautical mile is the mainstay of the navigation due to its close relation with degrees and minutes. It is relatively easy to measure distances on maps in nautical miles and can be easily read and referred to. I sure Thank You This was a Very Helpful Thread