Four Guardian Hills

The ridges enclosing a site are named after four guardian creatures: the tortoise supporting the back, the bird facing the front, the dragon on the left and the tiger on the right. When all four enclose evenly, the site is held to store wind well. Left and right are read from inside the building looking out toward the facing direction, not from behind it (facing south, east is the dragon and west the tiger). MYEONG now judges all four from elevation data (global 30 m): for each direction it takes the elevation angle of whatever blocks the most sky — height against distance — and from those reads how far the rear and flanks enclose the site and whether the front stays open. Two limits remain: a 30 m grid smooths very narrow ridges, and tall buildings are absent from terrain data, so they are counted on a separate 'artificial hills' axis (which dominates in a city).