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## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Uk data
From: Paul Hirose
Date: 2021 Jun 27, 22:30 -0700

```On 2021-06-26 22:00, Geoffrey Kolbe wrote:
> Strange... when it asks for the time, you can only enter hours and
> minutes, but no seconds. The other thing is it asks for longitude
> followed by latitude. I would expect latitude followed by longitude and
> I entered this incorrectly first time around.

The "longitude before latitude" format is common in astronomy. For
example, see the Astronomical Almanac list of observatory coordinates
and the JPL Horizons online calculator.

https://archive.org/details/binder1_202003/page/n523/mode/2up

https://ssd.jpl.nasa.gov/horizons.cgi?CGISESSID=5b4a2d2e43fd07198baa5bd6e8a4e3e7&s_loc=1#loc

On the other hand, to input site coordinates in the USNO MICA
application you enter latitude then longitude, but the order is reversed
in the output display.

Another convention sometimes encountered in astronomy is terrestrial
longitude increasing east from 0 to 360. The Horizons documentation says,

"East longitude is measured positively to the east (0 to 360 degrees)
from the prime meridian. Exceptions are the Earth, Moon and Sun where
longitude has historically been measured both east and west of the prime
meridian 0 to 180 degrees. Though these bodies are direct rotators,
longitude is nonetheless measured positively to the east on this system,
0 to 360 degrees, due to historical precedence. If the positive west
longitude of a site on these 3 bodies is given, it should be input here
as positive east longitude, which would be (360 - West Longitude). If
the negative east longitude is given instead, for these exceptions only,
one can input the negative east longitude. It will be converted to a
positive east longitude on output, however."

In other words, the system allows you to enter longitude 10° W as -10,
but in the output it's +190°.

I don't use longitude greater than 180 myself, but have encountered it
in data from an external source. No problem, except that software with
over-zealous error checking rejected the longitudes.

--
Paul Hirose
http://sofajpl.com/
```
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