How to Determine Qiblah Direction 
The praying person should acquire knowledge about qiblah direction. The testimony of two just people who give their testimonies on basis of sensible indications is enough. If that proves impossible, one should make every effort to know the direction of qiblah and act according to the resulting guess. Then, if one determined the direction of qiblah through reliable methods and prayed to the same direction but came to know later that it was the wrong direction, their prayer would be valid if the deviation was less than 90 degrees. However, if the deviation was more than 90 degrees, then one should repeat the prayer in case that its time is not over yet, but it requires no qaḍā’ if the prayer time is already over.

To Determine Qiblah through Scientific Rules
It suffices to get confident about qiblah direction through scientific rules.

Qiblah Showed by a Compass, a Masjid or a Grave
It is correct to rely on a compass provided that it makes the mukallaf confident with respect to the direction of qiblah and it should be acted upon. Otherwise, there is no problem in relying on the niches of masjids or the graves of Muslims in determining the direction of the qiblah.