Three browser-based tools for classic land-surveying calculations, using gons (400 gon = full circle) and the surveying convention: Y axis points North, X axis points East, bearings measured clockwise from North.
| Page | Purpose |
|---|---|
| topo.html | Distance and bearing between two points A and B |
| rayonement.html | Polar survey — locate point M from a station S using a reference R, an angle and a distance |
| intersection.html | Triangulation — locate point M from two stations A, B and the angles α, β observed at each |
All three share topo.css and are linked by a top navigation bar.
Open any HTML file directly in a browser — no server needed.
Bearing (gisement) — the angle from North to the direction A→B, clockwise. Computed from Δx = x₂ − x₁ and Δy = y₂ − y₁ using atan, with a quadrant-dependent offset (0, 100, 200 or 300 gon) so the result lies in [0, 400).
Distance — Euclidean: d = √(Δx² + Δy²).
Polar survey (rayonnement) — given a station S and a reference R, the bearing S→R orients the instrument. Adding the observed angle α gives the bearing S→M, and the new point is projected at the measured distance:
G_SM = G_SR + α
x_M = x_S + d · sin(G_SM)
y_M = y_S + d · cos(G_SM)
Triangulation (intersection) — given two stations A, B and the angles α (at A) and β (at B) toward the unknown point M, the third angle is γ = 200 − α − β (gon). The law of sines gives the side lengths, and the bearing A→M is G_AB ± α depending on which side of AB the point lies:
AM = AB · sin(β) / sin(γ)
G_AM = G_AB ± α
x_M = x_A + AM · sin(G_AM)
y_M = y_A + AM · cos(G_AM)
projet-topographique/
├── README.md
├── topo.css # shared styles
├── topo.html # distance + bearing
├── rayonement.html # polar survey
└── intersection.html # triangulation