I am not a scientist, so maybe I am wrong, or misunderstood something here, but I think they can still use the sun or moon's position to navigate or determine their position.
At least, based on OP's comments, I assume that they still have a sun and moon like Earth's.
Here are some links that explain it better:
Using the sun to hold a bearing
This technique uses the sun or moon to keep you heading in the right
direction. It doesn’t replace the use of a compass, but instead helps
you to maintain a certain route. Using the sun, or at night the moon,
gives you a reference to the cardinals of the compass.
- Face the direction (bearing) you are going to travel and reach out with your arm as if you were going to grab hold of the sun and hold
this position for a couple of seconds: this helps imprint your
orientation to the sun.
- Lower your arm and move forward, keeping in mind where the sun should be in relation to you.
- You can travel for 10 mins on a single bearing using this technique before you need to repeat it.
- If the sun is behind you, use your shadow. Reach out and hold your arm parallel with your shadow and hold this position for a couple of
Using this technique frees you up from having to constantly refer to
your compass or map and instead allows you to concentrate on your
surroundings and enjoy the scenery. Mountain rescue dog handlers
routinely employ this method so they can concentrate on their dog and
visibly search the area themselves.
Accurate angle measurement evolved over the years. One simple method
is to hold the hand above the horizon with one's arm stretched out.
The width of the little finger is an angle just over 1.5 degrees
elevation at extended arm's length and can be used to estimate the
elevation of the sun from the horizon plane and therefore estimate the
time until sunset. The need for more accurate measurements led to the
development of a number of increasingly accurate instruments,
including the kamal, astrolabe, octant and sextant. The sextant and
octant are most accurate because they measure angles from the horizon,
eliminating errors caused by the placement of an instrument's
pointers, and because their dual mirror system cancels relative
motions of the instrument, showing a steady view of the object and
Navigators measure distance on the globe in degrees, arcminutes and
arcseconds. A nautical mile is defined as 1852 meters, but is also
(not accidentally) one minute of angle along a meridian on the Earth.
Sextants can be read accurately to within 0.2 arcminutes, so the
observer's position can be determined within (theoretically) 0.2
miles, about 400 yards (370 m). Most ocean navigators, shooting from a
moving platform, can achieve a practical accuracy of 1.5 miles (2.8
km), enough to navigate safely when out of sight of land.
Using a marine sextant to measure the altitude of the sun above the horizon
Latitude was measured in the past either by measuring the altitude of the Sun at noon (the "noon sight"),
Lunar distance Main article: Lunar distance
The older method, called "lunar distances", was refined in the 18th
century and employed with decreasing regularity at sea through the
middle of the 19th century. It is only used today by sextant hobbyists
and historians, but the method is theoretically sound, and can be used
when a timepiece is not available or its accuracy is suspect during a
long sea voyage. The navigator precisely measures the angle between
the moon and the sun, or between the moon and one of several stars
near the ecliptic. The observed angle must be corrected for the
effects of refraction and parallax, like any celestial sight. To make
this correction the navigator would measure the altitudes of the moon
and sun (or star) at about the same time as the lunar distance angle.
Only rough values for the altitudes were required. Then a calculation
with logarithms or graphical tables requiring ten to fifteen minutes'
work would convert the observed angle to a geocentric lunar distance.
The navigator would compare the corrected angle against those listed
in the almanac for every three hours of Greenwich time, and
interpolate between those values to get the actual Greenwich time
aboard ship. Knowing Greenwich time and comparing against local time
from a common altitude sight, the navigator can work out his