What is being drawn
Astrocartography turns a birth chart into a world map. Fix the moment of birth, then vary the place of observation. Every location from which Pluto would have been exactly rising, setting, culminating or at the lowest point falls on one of four lines.
The method comes from the 1970s and is credited to Jim Lewis, who developed it and named it. It is a modern technique that relies on computation. Its one inheritance from older astrology is the treatment of angularity, the rule that a planet standing on an angle is emphasised. Pluto was discovered in 1930, so its symbolism is newer still.
Two straight lines and two curves
The Pluto MC line covers the longitudes at which Pluto was culminating, on the meridian overhead, and the IC line those at which it was at the lowest point, on the meridian below. A meridian is a fixed great circle through both poles, so these lines run straight north to south whatever the latitude.
The AC and DC lines mark rising in the east and setting in the west, and they are curves. The horizon sits at an angle to the ecliptic that changes as latitude changes, so the point of the ecliptic that is rising drifts, and the line bends with it. At high latitudes the bend becomes severe. This distinction is missing from most descriptions, which show four similar lines per planet and leave the reader with no way to make sense of what an actual map does in the far north.
What Pluto's lines are read for
Pluto is read as power, compulsion, buried material, control and the things that will not stay hidden. The MC line is described as public position with real power attached, work that involves other people's crises, money or secrets, and a reputation that provokes strong reactions. The difficulty stated alongside it is exposure and conflict over control.
The IC line is read as a private life in which the family past presses hard, and as a place of thorough personal change. The AC line is described as being met as intense and hard to ignore, with the caution being an appetite for control. The DC line reads through others, associated with binding relationships and with power struggles inside them.
That vocabulary is heavier than the technique can carry. These are the meanings a tradition has attached to a symbol, not a description of what will happen to anyone. Nothing here is a warning about a city.
Orb, and the line between the exact and the conventional
A line is normally read as active within a few hundred kilometres, and the number repeated across the literature is seven hundred to eight hundred, with the reading strongest exactly on the line. That orb is a convention rather than a measured range. It persists because it is convenient, and practitioners who prefer four hundred are not doing anything less careful.
The framing to hold onto is that astrocartography is geometry applied to a symbolic system. The geometry is exact and computable, which is why the lines can be drawn to the kilometre and why every program agrees on them. What a Pluto line means where it crosses a particular city is convention supplied by readers, and it should be weighed as interpretation. Do not treat it as a reason to move, or as a reason not to.
Parans mark latitudes where two planets are angular at once, and a relocated chart shows how the houses redistribute for a chosen city, which is a separate question from which lines run nearby.
Questions people ask about this
What does a Pluto line signify?
Power, compulsion, buried material and thorough change, with the angle deciding the emphasis. It is a symbolic reading rather than a statement about what a place will do.
Are Pluto lines dangerous?
No. The language used about them is dramatic, but the technique cannot support claims of that kind, and this page treats no line as good or bad fortune.
Why is the Pluto DC line curved and the MC line straight?
The MC line lies on a meridian, a fixed circle through the poles, so it is straight. The DC line follows the setting horizon, whose angle to the ecliptic depends on latitude, so it curves.
What orb applies?
The same convention as any other line, roughly seven hundred to eight hundred kilometres either side, strongest on the line itself. It is a habit of the literature, not a measured effect.
Does Pluto no longer being a planet change anything?
Astrologically, no. The reclassification in 2006 was an astronomical decision about categories, and astrologers who used Pluto before it continue to use it on the same terms.
Who developed astrocartography?
Jim Lewis, in the 1970s. It is a modern technique built on the older principle that a planet on an angle of the chart is emphasised.