You can get a more precise latitude (in the sense we use the term) measurement by measuring the angle of the ecliptic with the horizon. Shoot any two other bodies in the system that happen to be reasonably close to the horizon; with 8 to choose from, that shouldn't be hard (and assuming they're all pretty much coplanar, which I believe is the case). Your latitude is the angle between that line and a vertical line.

If the coplanarity constraint isn't met, you need an ephemeris to pull off the trick, but it still works.

Combine that with "solar latitude" as Leonard describes and you can get a very precise position fix. Actually, you'll get a couple of solutions, one on each side of the noon meridian, but (a) you'll usually have a rough idea where you are so you'll know which one to pick, and (b) failing that, you can disambiguate using a compass.

On Wed, Mar 8, 2017 at 6:00 AM, (via tml list) <xxxxxx@simplelists.com> wrote:
On 5 Mar 2017 at 9:02, Jeffrey Schwartz wrote:

> There is very, very limited ocean travel - Sailing ships on the trade
> winds that are pretty regular, but navigation is a bit freaky with no
> good clocks and no noon-sun shoot.

Actually, shooting the sun will tell you how far from the "noon pole"
you are. That places you on a circle. Call it solar latitude.

Since the planet *has* to have a magnetic field to be habitable
(don't ask how it maintains it) because of flares from the star (red
dwarves are prone to flares), comparing the direction of the sun with
north, places you at one point on the circle.

It won't be nearly as accurate as what we are used to, but it'd
likely place you within a few dozen miles. Not great for avoiding
reefs or the like, but usable for a rough idea of where you are.

The solar latitude will be a lot more accurate than the "magnetic
longitude". So you won't have a circle of uncertainty in your
position. More of an ellispe with the long axis running along the
line of solar latitude.

--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com


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