Earthcentric grid.

Equator and poles based upon Earth’s daily spin projected onto celestial surroundings.

Divisions from equator to North pole are positive numbered lines of latitude to +90 degrees.

Divisions from equator to South pole are negative numbered lines of latitude to -90 degrees.

Divisions from pole to pole across the equator are 24 lines of longitude matching hours of daily rotation with each hour subdivided by 60 arc minutes each of which is subdivided by 60 arc seconds.

Since Earth’s orbit of the Sun is not an even number of days, leap years and leap centuries are necessary to synchronize timing.

Also, since Earth “wobbles” due to precession in a cycle of approximately 26,000 years, this grid is redrawn every 50 years (an epoch) to synchronize with celestial surroundings.
In short, our “modern” Earthcentric grid is not nearly as stable over long periods of time as the galactic coordinate model for navigation of the Solar System to quite a distance beyond Pluto’s orbit.

As we explore space, we also use the stars to calibrate the navigation system of the exploring vehicle. Once beyond the view of the planets outside the Solar System, we too will relearn the galactic reference system.