check-gap.js

([x, z, x0, z0, x1, z1] = [
  // (x, z)
  1302.07495, 5962.14648,
  // (x0, z0)
  -6000, -33900,
  // (x1, z1)
  6200, 32700,
].map(Math.fround));
([dz, dx, dz0, dx0, dz1, dx1] = [z1-z0, x1-x0, z0-z, x0-x, z1-z, x1-x].map(Math.fround));
([dx0dz, mdx1dz] = [dx0*dz, -dx1*dz].map(Math.fround));
([d0, d1] = [dz0*dx-dx0dz, -dz1*dx-mdx1dz].map(Math.fround));