There are places you arrive in and just unlock. You sleep better, talk more, meet people with no effort, get ideas. And there are places where everything costs you, the same person, the same work, and a feeling of pushing a door that will not open.

Anyone who has lived in more than one city knows this, and usually explains it by the obvious: the weather, the language, the friends, the stage of life. Those explanations are good, and sometimes they are enough. Except they do not explain every case, some people were happy in a place that was cold, expensive and where they knew no one, and unhappy in the city where they had everything.

Location astrology, or astrocartography, is an attempt to answer this. It is worth understanding how it works, and how far it actually goes, because this is one of the subjects where the most is promised.

First an important correction, because almost everyone gets this wrong: moving city does not change your birth chart. It was calculated for an instant and a place that already happened, and nothing can alter it.

What astrocartography does is something else. It takes the sky of your birth, the positions of the planets at that exact instant, and asks: at which points on Earth was each planet rising, setting, or at the top of the sky at that moment? The answer is lines drawn on the map of the world.

It is pure geometry, and it is worth knowing this because it demystifies the whole thing: the lines are not anyone's opinion. They are calculable, and two people who do the maths arrive at the same lines. What the lines mean is where the interpretation comes in.

The traditional reading is direct: near a line for a given planet, that planet's themes tend to show up more in your life in that place.

A Venus line is associated with affection, pleasure and social ease. A Mars line, with energy, friction and initiative. A Saturn line, with weight, responsibility and slow building. A Jupiter line, with expansion and opportunity. And there is a difference between the line where the planet rises, more tied to identity and to how you come across there, and the one where it sits at the top of the sky, more tied to career and public life.

There is also a distinction that changes how the technique should be used and is almost never explained: the lines do not describe the place. They describe you in that place. Two people can live on the same street and have completely different lines there, because they were born at different instants, which is the opposite of saying a city is good or bad.

The level of detail can go far, and that is exactly where it is worth holding back the enthusiasm. It is one thing to say a region tends to favour a certain theme; it is another to say which street of which neighbourhood. The first is a reading. The second is a precision the technique does not have.

This technique it guarantees nothing. Nobody gets rich from living on a Jupiter line, and nobody falls ill from living on a Saturn line. There is no study that backs up any of these claims, and it is honest to say so in a text that presents them.

It it does not decide a move and it should not. Moving city involves visa, job, money, language, a child's school, family left behind and healthcare, and these factors weigh far more than any line. A reading that makes someone choose a country by a symbol, ignoring that list, has done real damage.

And it does not compete with the obvious. If you are unhappy in a city where you are isolated and out of work, the explanation already exists and needs no astrology.

What is left is what is left in everything here: one more criterion in a list you are already building, and a vocabulary for an experience you have already had.

There is a way of using this that is much better than any prediction, and it is almost never suggested: test it against your own biography.

Take the cities where you have lived, where you have spent time, even the ones you travelled to where something happened. Put them on the map. And see whether the descriptions match what you actually lived there.

It is worth doing this carefully, because memory cooperates with whoever wants to believe: write down what you remember of each place before before looking at the lines, and only then compare. Done the other way round, any chart matches any life.

This exercise is honest because it can go wrong, and that is its whole advantage. If the lines match nothing in your experience, you found that out before deciding anything based on them. A technique you have checked is worth more than one you have only read about, and this is one of the few where you actually can check it.

This is the most time-dependent reading of all, and it is not a matter of quality, it is a matter of possibility. The lines depend on where each planet stood relative to the horizon and the meridian at the exact instant of birth, and that changes by the minute.

It is the harshest difference in this family of readings, and it has a simple number behind it: the Earth turns fifteen degrees an hour. A fifteen-minute error shifts the lines by hundreds of kilometres. A one-hour error throws them into another country. Without an exact time, there is no astrocartography, and anyone offering one without it is handing over a pretty, empty drawing.

If your birth time is approximate, “it was in the morning”, “I think around three”, it is worth knowing this before buying anything of this kind. It is the one astrological product where the time is not a bonus: it is the requirement.

It is worth ending with the practical part, because that is what these texts usually lack most. A decision to move is made with a list, and the list has items that are not symbolic.

Visa and what it allows. Recognition of your degree. Cost of living compared with the local salary, not the one back home. Language, and how long until you can work in it. Healthcare and what it covers for a foreigner. Distance from family and the real cost of an emergency flight. And the weather, which seems like a detail and is the thing most people complain about after the first winter.

And there is one item almost everyone forgets, and it decides many a failed move: the network. Anyone who moves to a city where they know two people spends the first year rebuilding what they already had in place where they came from, and that cost does not show up on any spreadsheet, only in the third month.

A place reading comes in alongside that list, not in its place. It tends to work best in one specific moment: when there are two or three options the list cannot settle, and the person is stuck. Then one more criterion helps you decide, which is quite different from deciding for you.

This technique is modern, and it is worth saying so because almost no one does. Astrocartography as it is known today was created in the nineteen seventies by Jim Lewis, an American astrologer, who trademarked the name and popularised the maps with lines on them.

It only became possible because the calculation of projecting planetary positions onto the surface of the Earth needs a computer, before that, nobody drew that by hand for a client. It is a technique that technology created, not an ancient wisdom recovered.

It is worth saying this does not disqualify it. A new technique can be a good one, and age was never proof of anything, astrology carries plenty from two thousand years ago that does not hold up. What changes is the kind of credit it can claim: a fifty-year-old practice does not have behind it the generations of use that are usually cited as a guarantee.

There are precursors, and it is fair to name them: mundane astrology has always linked places to signs, and that list is old. But the idea that the your chart draws lines across the world is fifty years old, and knowing that helps calibrate how much to ask of it.

And the questions that come up most on this subject, with the short answer: