Jump to content


Photo

decimal degrees or degrees and minutes? *DELETED*

  • Please log in to reply
12 replies to this topic

#1 rnc39560

rnc39560

    Surveyor 1

  • *****
  • Posts: 1806
  • Joined: 23 Jul 2013
  • Loc: MS coast

Posted 09 November 2013 - 05:35 PM

Post deleted by rnc39560

#2 SkipW

SkipW

    Ranger 4

  • -----
  • Posts: 337
  • Joined: 03 Feb 2011
  • Loc: Oklahoma, USA

Posted 09 November 2013 - 05:42 PM

?

Location latitude and longitude are almost always specified in degrees. Do you mean degrees and minutes vs. decimal degrees?

#3 rnc39560

rnc39560

    Surveyor 1

  • *****
  • Posts: 1806
  • Joined: 23 Jul 2013
  • Loc: MS coast

Posted 09 November 2013 - 06:35 PM

Yes, that's what I meant. I should've been more specific. There, fixed it. Thanks. :)

#4 SkipW

SkipW

    Ranger 4

  • -----
  • Posts: 337
  • Joined: 03 Feb 2011
  • Loc: Oklahoma, USA

Posted 11 November 2013 - 11:54 PM

Degrees, minutes and seconds are traditional but are a pain to work with. Degrees and decimal minutes are not unusual. Decimal degrees are easiest to work with and becoming more common.

None are wrong; what are you trying to do?

#5 rnc39560

rnc39560

    Surveyor 1

  • *****
  • Posts: 1806
  • Joined: 23 Jul 2013
  • Loc: MS coast

Posted 12 November 2013 - 08:55 AM

Was just curious. I have seen both used occasionally, and was wondering WHICH seemed to be more understood and which was more often used.

#6 Tony Flanders

Tony Flanders

    Voyager 1

  • *****
  • Posts: 11179
  • Joined: 18 May 2006
  • Loc: Cambridge, MA, USA

Posted 12 November 2013 - 09:07 AM

Was just curious. I have seen both used occasionally, and was wondering WHICH seemed to be more understood and which was more often used.


Both are very common. To make matters worse, right ascension (RA) is sometimes measured in hours and sometimes in degrees, where 1 hour = 15 degrees.

It's just another example of the glorious lack of standardization that makes astronomy so entertaining.

If you think about it, it's pretty mind-boggling that despite massive inconvenience we're still using a base-60 system for angular measures whose heyday was in ancient Sumeria. It was already obsolete by the time the Greeks adopted it 2,500 years ago.

#7 rnc39560

rnc39560

    Surveyor 1

  • *****
  • Posts: 1806
  • Joined: 23 Jul 2013
  • Loc: MS coast

Posted 12 November 2013 - 09:54 AM

Thanks Tony.

#8 PeterR280

PeterR280

    Apollo

  • *****
  • Posts: 1185
  • Joined: 27 May 2013

Posted 12 November 2013 - 10:06 AM

Longer time periods should be based on fortnights.

#9 SkipW

SkipW

    Ranger 4

  • -----
  • Posts: 337
  • Joined: 03 Feb 2011
  • Loc: Oklahoma, USA

Posted 12 November 2013 - 10:37 PM

Great suggestion! The fortnight is, I think, the longest period of time with a constant length.

#10 Starry eyes

Starry eyes

    Vostok 1

  • -----
  • Posts: 131
  • Joined: 30 Apr 2010

Posted 12 November 2013 - 11:17 PM

I'd like to point out that as a sailor we use one minute of latitude equal to one nautical mile. Also as a surveyor we use minutes & seconds as a matter of course. Also one R.A. " is the angular distance in R.A. traversed in one R.A. second of time which is tied to the rotational period of the Earth. So these units are tied to fundamental properties of our Earth. :) :)

#11 brianb11213

brianb11213

    Cosmos

  • *****
  • Posts: 9047
  • Joined: 25 Feb 2009
  • Loc: 55.215N 6.554W

Posted 13 November 2013 - 03:52 AM

Longer time periods should be based on fortnights.

Funny you should bring this up. Timings for DEC computers (PDP, VAX - remember them?) were usually quoted in microfortnights (a little larger than a second). Really confused anyone not in the know.

I don't see why "long" periods should not be measured in megaseconds (approx. 11.6 days), gigaseconds (approx. 31.7 years), teraseconds & petaseconds. The current age of the solar system is approximately 142 Ps & even the age of the universe (430 Ps) is not sufficiently long to make the exasecond a practical unit for "historical" events, though the Es is insufficient for projections of cosmological evolution into the distant future.

#12 Tony Flanders

Tony Flanders

    Voyager 1

  • *****
  • Posts: 11179
  • Joined: 18 May 2006
  • Loc: Cambridge, MA, USA

Posted 13 November 2013 - 07:49 AM

I'd like to point out that as a sailor we use one minute of latitude equal to one nautical mile.


True -- that's a very handy fact, useful for anybody (like me) who plays mentally with latitude and longitude. However, the fact that one sixtieth of one 360th of a meridian on Earth happens to be approximately the same as 1,000 full paces of the Roman army is entirely coincidental. Neither the Sumerians nor the Romans were aware of that fact when they established their respective measures.

One R.A. " is the angular distance in R.A. traversed in one R.A. second of time which is tied to the rotational period of the Earth.


Yes, of course. Measuring R.A. in time isn't arbitrary at all -- though measuring time in sixtieths gets us right back to those Sumerians again.

#13 Retsub

Retsub

    Vostok 1

  • *****
  • Posts: 131
  • Joined: 08 Dec 2006
  • Loc: Houston,Tx.

Posted 14 November 2013 - 12:55 AM

Wasn't it from those same people that we now use the wheel width for our cho-cho train tracks ? Thanks. *BW*






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics