Is the compass direction of a planet recorded by two different observers separated by some distance the same? I have a basic doubt. Say I am viewing Mars from my window and I used the compass app to get an approximate 2D direction. If at the same instant another person also observes Mars from their window. Say the other person is in the same city separated by a few kilometres. What will be the measured direction by me and the other observer. Will it be same or different?
Thanks
 A: Suppose your friend is nearly half way around the world from you at the same latitude.
You might see Mars on the south-eastern horizon while your friend will see it on the south-western horizon.
If you moved closer together, the directions would move more south and less east/west.
Keep moving closer and closer to each other and the directions will become closer and closer to being the same.
If you are only a few kilometres apart, your directions will be different, but almost identical.
To answer your question: they "will be different", but at that distance, unless you have extremely precise compasses, for all practical purposes, they "will be the same".
A: As you move north or south the angle between Mars and the horizon (its altitude) will change because the plane in which your local horizon lies is tipping one way or the other. As you move east or west the angle between the direction of Mars and north (its azimuth) will change because your local direction of north is changing.
To see a one degree difference in altitude you would need to move about $111$ km north or south (not by coincidence, this is exactly $60$ nautical miles). The distance you need to move east or west to see a one degree change in azimuth depends on your latitude - at the equator you need to move about $111$ km east or west, but at a latitude of $45^o$ you only need to move about $79$ km east or west.
To avoid confusion due to differences in local directions, astronomers generally use a global co-ordinate system such as equatorial co-ordinates and convert to local altitude and azimuth as necessary.
A: I believe it would be roughly the same? If two points on Earth, wich in my humble opinion I experience as flat and motionless, Mars , one of the seven wondering stars, would roughly be the same distance. Peace and Love to you all!
