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We could deploy planets and other celestial objects as references. Their displacement will be an issue since all systems and individual celestial objects keep moving but much advanced navigation systems should solve that
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Obviously, by the time space travel becomes commonplace there will already be an alternate coordinate system. Space travel couldn't become commonplace without one. >

Not so. The spinning of a planet determines these directions. If you take your right hand, make a thumbs-up sign, and orient it so that your fingers curl in the direction the planet is spinning, your thumb will point towards the north pole and the other directions will be consistent with earth.
From that we can get latitude angles without any arbitrary decisions. The only piece that is arbitrary is where you start numbering longitude. We can set some standard for that pretty easily though. For example, we could say that the point of highest elevation on the planet is longitude 0. That would give a complete coordinate system for any planet >

Also if you hold a wire with your right hand, and thumb pointing in the direction of current flow, your curled fingures match the rotation of the magnetic field generated by the flowing current through the wire. >

We could deploy planets and other celestial objects as references. Their displacement will be an issue since all systems and individual celestial objects keep moving but much advanced navigation systems should solve that >

Longitude and latitude didn't exist before we started having ocean-bound ships.  Once we have space ships, we'll invent star charts.
I think it'll be harder to standardise calendars and time.  How will age work if you live on a planet where  1 year =  4 Earth months? >

Good luck with the space flight thing if you can’t handle tridimensional coordinates and unit/origin/orientation conversions
It’s the kind of math that could be handled by a Spectrum 48k >

You are correct that the concepts of cardinal directions (North, South, East and West) and latitude and longitude, which are based on the characteristics of the Earth, would not be useful when navigating in space. Because we are on earth and it's rotation create this point of reference.
When space travel becomes more commonplace, it is likely that a new system of navigation will be developed that is better suited to space travel. The Global Positioning System (GPS) is a good example of such a system. GPS uses a network of satellites orbiting the Earth to provide accurate location and navigation information to users on the ground. But as you point out, this system is only useful on and around Earth, it will not work in deep space.
In order to navigate in deep space, spacecraft would have to rely on other methods such as astronomical observations, radar, and radio signals. Some spacecrafts use the natural objects such as the sun, stars, or even distant galaxies to navigate.
It's important to note that current space missions rely on a combination of methods, such as ground-based radar, spacecraft telemetry, and optical tracking, to determine the positions of spacecraft in flight. But as space travel becomes more advanced and more common in the future, it's likely that new technologies and systems will be developed to make space navigation more accurate, efficient, and accessible.
It's also likely that a universal point of reference will be developed for deep space travel, it could be a distant galaxy or a quasar or any other natural objects that are visible from different parts of the universe. >

They already solve this a long time ago. Go watch a documentary on the Voyager probes. >

"yeah can we meet 10,000km away from mars in the direction of Andromeda galaxy?" >

There are other coordinates and measurments for space and have been for some time >

This is a friendly reminder to read our rules.
Remember, /r/Showerthoughts is for showerthoughts, not "thoughts had in the shower!"
(For an explanation of what a "showerthought" is, please read this page.)
Rule-breaking posts may result in bans. >

Obviously, by the time space travel becomes commonplace there will already be an alternate coordinate system. Space travel couldn't become commonplace without one. >

Not so. The spinning of a planet determines these directions. If you take your right hand, make a thumbs-up sign, and orient it so that your fingers curl in the direction the planet is spinning, your thumb will point towards the north pole and the other directions will be consistent with earth.
From that we can get latitude angles without any arbitrary decisions. The only piece that is arbitrary is where you start numbering longitude. We can set some standard for that pretty easily though. For example, we could say that the point of highest elevation on the planet is longitude 0. That would give a complete coordinate system for any planet >

Also if you hold a wire with your right hand, and thumb pointing in the direction of current flow, your curled fingures match the rotation of the magnetic field generated by the flowing current through the wire. >

Longitude and latitude didn't exist before we started having ocean-bound ships.  Once we have space ships, we'll invent star charts.
I think it'll be harder to standardise calendars and time.  How will age work if you live on a planet where  1 year =  4 Earth months? >

"yeah can we meet 10,000km away from mars in the direction of Andromeda galaxy?"