[HN Gopher] 111,111.1 meters is reliably 1 degree of latitude
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111,111.1 meters is reliably 1 degree of latitude
Author : mholt
Score : 37 points
Date : 2023-08-27 17:00 UTC (6 hours ago)
(HTM) web link (gis.stackexchange.com)
(TXT) w3m dump (gis.stackexchange.com)
| NelsonMinar wrote:
| This post also has a nice rule of thumb that 111,111 *
| cos(latitude) meters is 1 degree of longitude. I like the
| correction! In practice you can use some simple constants; 25deg
| is about 100,000 meters. 44deg is about 80,000 meters. 57deg is
| about 60,000 meters.
| delta_p_delta_x wrote:
| The metre was originally defined in 1791 as one ten-millionth of
| the quarter-meridian, or ninety degrees of arc, through Paris.
|
| It then follows straightforwardly that 1deg [?] 1/90 x 10^7 m =
| 111 111.111... m.
|
| It also follows straightforwardly that the circumference of Earth
| is approximately forty million metres, or 40 000 km.
| aappleby wrote:
| And a 32-bit integer can represent latitude or longitude to an
| accuracy of around 1 centimeter :D.
| OscarCunningham wrote:
| Call that a long long.
| [deleted]
| gp wrote:
| 1 nautical mile (~6076 ft) is exactly one minute of arc at the
| Earth's equator.
|
| As a sailor, I wish that all miles were nautical miles because
| they have a real meaning. What good is 5280 feet?
| _dain_ wrote:
| I wish those medieval people had defined it as 5040 feet, then
| it would be divisible by 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14,
| 15, 16, 18, 20, 21, 24, 28, 30, 35, 36, 40, 42, 45, 48, 56, 60,
| 63, 70, 72, 80, 84, 90, 105, 112, 120, 126, 140, 144, 168, 180,
| 210, 240, 252, 280, 315, 336, 360, 420, 504, 560, 630, 720,
| 840, 1008, 1260, 1680, and 2520.
| chungy wrote:
| Connecting 1 mile to 5280 feet happened many centuries after
| the medieval period. Such precision wasn't really possible
| nor desired before the 18th century.
|
| To be specific, 5280 feet = 1 mile didn't happen until 1959
| and the United States needed higher precision and remove all
| the fuzziness out of the units. It might be inconvenient on
| some aspects, but it was also "close enough" to what miles
| were already established to be.
| _dain_ wrote:
| >To be specific, 5280 feet = 1 mile didn't happen until
| 1959 and the United States needed higher precision and
| remove all the fuzziness out of the units. It might be
| inconvenient on some aspects, but it was also "close
| enough" to what miles were already established to be.
|
| uh what? are you sure you're not mixing that up with the
| international geophysical year or something? the mile has
| been 1760 yards since before the US even existed. it's
| called the imperial system because of the british empire.
| they couldn't have done the great trigonometrical survey of
| india without an accurate mile.
| delta_p_delta_x wrote:
| Most other 'mile's are derivatives of the Roman mile which
| developed somewhat independently of the English units (foot,
| yard, inch, barleycorn, etc), ergo the weird conversion
| factors.
|
| In fact, 1 nmi [?] 1.852 km exactly.
|
| Also from the original definition of the metre: 1/60 x 1/90 x
| 10^7 = 1851.85185185... m.
|
| Inter-convertability was a defining trait of SI (or more
| precisely, its predecessors, MKS and CGS) from the very outset,
| which is why we have 1 m [?] 1 s [?] 1 kg [?] 1 N [?] 1 Pa [?]
| 1 J [?] 1 A [?] 1 C [?] 1 V [?] 1 O [?] 1 F [?] 1 W [?] 1 Wb
| [?] 1 T [?] 1 H [?] 1 Hz (I use '[?]' loosely here to suggest
| conversion factors, rather than its usual meaning of
| equivalence).
|
| The only outliers in the SI are the kelvin, the mole, and the
| candela (and derived units from these). The former two are
| dealt with straightforwardly with the Boltzmann and Avogadro
| constants. I have issues with the presence of the candela in
| the SI.
| burlesona wrote:
| Interestingly, a mile was originally the less surprising 5000
| feet. But in the 1500s the English changed the mile to be 8
| furlongs, as that made for much easier math around the
| agricultural measurements of the time.
|
| https://en.m.wikipedia.org/wiki/Furlong
| opwieurposiu wrote:
| A mile is 5280 feet because it is 80 chains (survey chains)
| long. The chain's length is a byproduct of English land tax
| laws which were by the acre.
|
| The roman mile was 1000 paces, or 5000 feet, which made a bit
| more sense.
|
| https://en.wikipedia.org/wiki/Gunter%27s_chain
| HPsquared wrote:
| And 1 nanosecond at light speed [?] 1 foot
| stereo wrote:
| And the number of seconds in a year is p*10^7, or close enough.
| chungy wrote:
| That's remarkably close to reality. I'm impressed :)
| $ units c ft/ns * 0.98357106
| maxmcd wrote:
| Admiral Grace Hopper Explains the Nanosecond:
| https://youtu.be/9eyFDBPk4Yw
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(page generated 2023-08-27 23:00 UTC)