Back in June I composed a story around the 45th parallel, which runs through brand-new Hampshire. The state has actually two (two!) historic markers noting the you space halfway in between the equator and also the north Pole at that point. Except you’re no really due to the fact that of geometry, as you can learn by reading my sterling prose.

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I got an email today pointing me to a 2000 article in the Journal of the imperial Astronomical culture of Canada (http://adsabs.harvard.edu/full/2000JRASC..94…48B) about this an extremely topic. The email is indigenous a guy named thomas Murray in Scotland who runs a website around this topic dubbed latitudes information.

Here is the article:

“Several years ago there to be a little controversy in Nova Scotia worrying the correct ar of a highway monument close to Stewiacke, Nova Scotia. In the 1930s, a roadside mite along course 2 was erected to indicate that it was one location in Nova Scotia the is midway in between the phibìc Pole and the Equator. The marker to be 16 kilometres north of the 45th parallel, whereby some human being felt it must be located. The old marker is correct, and also if you are driving southern on Highway 102 toward Halifax, you will see an additional sign simply north of departure 11 to Stewiacke announcing the you space at that distinct line the latitude: 45° 8 ́.65 N, midway indigenous the pole come the equator. The dispute occurs since a midway allude can be defined in a couple of ways.

“The most obvious meaning is to usage a suggest on the 45th parallel (45°N),which is the latitude numerically midway in between the Equator at 0°N latitude and also the north Pole in ~ 90°N latitude. The exactly method, however, is to halve the distance along the surface ar of the Earth in between the Equator and North Pole. The latter procedure entails more challenging calculations than is the instance with the very first definition. Only if the planet were a perfect round would the midpoint mentioned by both methods happen at 45°N latitude.”

“Note the the halfway suggest is no at 45°N, yet falls slightly north of the parallel. Halfway is established to be in ~ 45° 8 ́ 39” that latitude.”

Personally computed using Charles Karney’s “Online geodesic calculations using the GeodSolve utility”: https://geographiclib.sourceforge.io/cgi-bin/GeodSolve “GeodSolve is precise to about 15 nanometers (for the WGS84 ellipsoid)” or 0.000015 that a millimeter or 0.00000059 of one inch. In an email to me native Charles Karney: “The accuracy of 15 nanometers that ns quote is for courses up to half-way round the earth.”

Currently the finest fit reference ellipsoids for the earth / geoid, that have latitude-longitude based on them, room the GRS80 (1980) ellipsoid, and also the WGS84 (1984) ellipsoid. Because of this it renders sense to usage latitude-longitude based on the GRS80 ellipsoid or the WGS84 ellipsoid, because that the halfway latitude. An instance if one uses a local ellipsoid: Computed in the Airy 1830 ellipsoid (Great Britain), the Earth’s equatorial circumference would it is in 3.604 km or 2.239 international miles less, than computed in the WGS84 / GRS80 ellipsoid, and also the Earth’s polar or meridional circumference 3.359 km or 2.087 miles less. Because of this using a neighborhood datum such as NAD27 (Clarke 1866 ellipsoid) because that halfway, does not make sense. The current datum because that the USA, and Canada, is NAD83, i m sorry is based on the GRS80 ellipsoid. Though NAD83 will certainly be changed in phibìc America by NATRF2022 in 2022, but NATRF2022 will retain the GRS80 ellipsoid. GRS80 is civilian and also has replaced neighborhood ellipsoids in many countries, whereas WGS84 is operation by the United states Department the Defense. Yet WGS84 is supplied by handheld navigating grade, advertisement grade, consumer grade GPSr / GNSSr; automotive navigation systems; smartphones; navigation systems because that aircraft, ships; Google Earth; Wikipedia etc. Conversely, GRS80 is offered by Survey-Grade GNSS receivers for accurate and an accurate surveying, i.e. GRS80 is offered by surveyors, surveying & mapping organizations.

The difference in between halfway computed in both WGS84, and also GRS80 ellipsoidal distance, in latitude, i.e due north-south, is 0.078757 of a millimeter or 0.003101 of one inch. The WGS84 latitude is 0.078757 mm or 0.003101 customs farther north, 보다 the GRS80 latitude. Incidentally the Earth’s polar or meridional circumference computed in the GRS80 ellipsoid, is just 0.32906 that a millimeter or 0.01296 that an inch shorter, 보다 that computed in the WGS84 ellipsoid.

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The nationwide Geodetic survey (USA) inverse Computation, and also its front Computation: https://www.ngs.noaa.gov/cgi-bin/Inv_Fwd/inverse2.prl, and also https://www.ngs.noaa.gov/TOOLS/Inv_Fwd/Inv_Fwd.html assume that ranges computed in the GRS80 (1980) ellipsoid, and also the WGS84 (1984) ellipsoid are the same “GRS80 / WGS84”, however they actually compute in the GRS80 ellipsoid. Using National Geodetic inspection (USA) train station Computation, and its front Computation: “Ellipsoid : GRS80 / WGS84 (NAD83)”, halfway computes together “LAT = 45 8 39.54374 North” (Latitude 45 degrees 8 minutes 39.54374 seconds North), which come the exact same precision is similar to that computed in the WGS84

**ellipsoid. “LAT = 45 8 39.54374 North” (45° 08’ 39.54374” N) is in latitude, i.e. early north-south, to a precision of 0.308707 of a millimeter or 0.012154 of one inch.**

2 Comments

Judy Roushon October 11, 2021 in ~ 3:21 pm

David, my husband says you need to acquire a job

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