Relocation chart
A relocation chart is a birth chart recast for a different city while keeping your moment of birth fixed. The signs and degrees of the planets stay the same, because the sky is the same everywhere at that moment. What changes is which houses the planets fall in and the positions of the Ascendant and MC; these depend on Earth's rotation and on the latitude and longitude where you are. So the same person who has the Sun in the 10th house in Istanbul might have it in the 9th house in London or the 7th house in New York.
A relocation chart is used to understand which areas of your life a place where you live, or are thinking of moving to, will bring to the fore. The strongest effect comes from planets close to the Ascendant, Descendant, MC and IC: a city where Venus is close to the MC can describe visibility and recognition in your career, while a place where Saturn is close to the Ascendant can describe a more serious period loaded with responsibility. Astrocartography maps follow the same logic and show these angle lines on a world map. Relocation requires an accurate birth time; a difference of a few minutes can change the Ascendant and the house boundaries.