Relationship Astrocartography — Composite Chart Lines Drawn on the World Map

What relationship astrocartography means

Locational astrology reads a single birth instant by asking where on Earth each planet was rising or culminating. Applied to a couple, the technique has to answer a methodological question first: whose instant?

Traditional practice treats the relationship as its own entity with its own chart — a composite built from the midpoint of every pair of bodies across the two natal charts. That composite has an instant, a set of positions and (by averaging the two birth locations) a notional birthplace. You can then ask of the composite exactly what you ask of a single-person chart.

The output is a world map with the composite's planetary lines: Venus-Asc runs somewhere, Jupiter-MC runs somewhere else, and cities near those lines are traditionally said to give the relationship as a pair, not either partner individually, room to express that theme. Practical moves — one partner's job, a visa, family proximity — matter more than any line. The map is a vocabulary for what a place asks of the pairing.

How the composite is built and its lines drawn

The composite chart is a midpoint-per-body construction: for each of the ten classical planets we take the shortest-arc ecliptic midpoint of partner A's and partner B's longitudes. The composite date is derived from the Moon's and Sun's midpoints projected back to a plausible instant. The composite place is the arithmetic mean of the two birth locations. This is the classical composite convention, not the Davison relationship chart (which we ship separately).

The composite chart's lines are then solved the same way single-person astrocartography is: at the composite instant, for each latitude between 80°S and 80°N, we invert the horizon equation for the longitude at which each planet rises (ASC family), culminates (MC family), sets (DESC) or under-culminates (IC). Solutions come out as polylines rendered over Natural Earth 110m coastlines in equirectangular projection. MC/IC families are lat-independent meridians by construction. Line rankings for any city are angular distances from the composite's ten planets on that place's horizon.

What you get

Once both partners' birth data is entered:

• A world map with the composite chart's forty planetary lines, filterable by planet and by angle family.
• A place search that ranks which composite lines run closest to any city — the same ranking algorithm as our personal astrocartography map.
• A composite-chart relocated horoscope for that place: the composite's planets re-housed against the destination's horizon.
• A short traditional reading of each line — what a composite Venus-ASC or composite Saturn-MC is said to colour for the pairing.

Reading the map for a pairing rather than a person

Same line vocabulary as personal astrocartography, but the subject is the relationship-as-entity. Composite Venus on the local ASC reads as the pairing's affection-and-beauty theme becoming personally visible in that place. Composite Saturn on the MC reads as structure-and-duty themes becoming publicly visible. Because the composite chart's Moon is already the mid-point of two Moons, its lines tend to speak to the relationship's emotional weather rather than either partner's private feelings.

Discipline: the map is one lens. Both partners' personal astrocartography maps are also in play, and any relocation decision that ignores visa categories, housing markets, employment or family proximity in favour of a line has gone badly wrong. Treat this tool as a conversation-structured-with-geometry, not as a decision algorithm.

A worked example, with real numbers

Two births at 17:30 UTC on 1 January 2000, one in London and one in Berlin. Composite bodies fall at the ecliptic midpoints of each matched pair — and because both partners share one birth instant, every planet is already at the same longitude, so the composite reproduces it exactly: composite Sun 10.60° Capricorn, composite Venus 1.84° Sagittarius, composite Moon 16.08° Scorpio, composite Saturn 10.39° Taurus. Only the angles change, because they are recomputed for the composite place — composite Ascendant 3.99° Leo, composite MC 10.66° Aries.

The composite place is the average of the two birth locations (roughly the Netherlands–Germany border, about 52° N, 6.6° E) and the composite instant is the shared birth time.

Ranking the composite lines against New York returns a Jupiter-ASC about 5.6° away and a Saturn-ASC about 5.9° away (the slow-planet lines coincide with the personal London chart's, since the composite and single-body longitudes are identical). Tokyo sits close to two composite lines: a Saturn-DESC about 3.7° away and the composite Moon-ASC about 4.0° away — traditionally 'the relationship's structure-and-duty line and its emotional weather both come to the fore here' for the pairing.

What this tool does not claim

No controlled study has demonstrated astrocartographic relocation effects for either an individual or a couple. Line placement is exact geometry. The interpretive tradition is cultural, and we label it as such. The composite-chart convention itself is contested — Davison, composite and synthesis-chart methods each give a different 'relationship chart', and there is no consensus on which is canonical.

Line placement uses the same Porphyry-era horizon geometry as our natal charts; solutions near the poles genuinely do not exist for some planets, so a line ending is data. With either partner's birth time unknown, the composite's angles inherit the uncertainty. Treat the map as approximate in that case. Calculations run entirely in your browser. Your birth data is never uploaded, never stored on a server, and never shared.

Relationship astrocartography vs personal astrocartography

Personal (`/tools/astrocartography`) maps the world from one birth instant — the lines describe places that colour an individual's chart. This tool maps the world from a composite instant derived from two charts — the lines describe places that colour the pairing as an entity. Most couples considering a move together use both maps and note where a line family appears on both readings; those overlaps are traditionally given the most weight. Local-space astrology (compass directions from a doorstep) is a third technique, shipped separately.

Our method in one line

Composite bodies from shortest-arc ecliptic midpoints of the two natal charts; composite date and place derived from the paired Sun/Moon midpoints and averaged location; forty lines solved numerically from sub-arcsecond astronomy (VSOP87/ELP via astronomy-engine) against the horizon equation at 4° latitude steps (bisection-refined); rendered over Natural Earth 110m coastlines. Reviewed by Dr. Amara Osei, Astronomy Reviewer.