satellite azim,elev to cartesian coords

azimElevToXY.js

const elevToHypLength = (elev, canvasSize) => {
  return canvasSize - (canvasSize * elev) / 89.99999999;
}

const deg2rad = deg => (Math.PI * 2 * deg) / 360;

const toFixedFloat = (num = 0, digitsAfterDecimal = 0) => parseFloat(num.toFixed(digitsAfterDecimal))

const getXY = (azim, elev, canvasSize) => {
	const hyp = elevToHypLength(elev, canvasSize / 2);
	const angle = deg2rad(azim % 90);

	const opp = toFixedFloat(Math.sin(angle) * hyp, 2);
	const adj = toFixedFloat(Math.cos(angle) * hyp, 2);

	// return x, y coords in the orientation of compass directions.
	// 0 = N, 90 = E, 180 = S, 270 = W

	// need to do some basic coord transforms because the triangle math won't work without 90 deg
	// triangles (degress 0-90 only), also to account for compass directions, which are rotated and
	// flipped, as opposed to standard math orientation

	if (azim >= 0 && azim < 90) {
		return [opp, adj];
	}

	if (azim >= 90 && azim < 180) {
		return [adj, -opp];
	}

  	if (azim >= 180 && azim < 270) {
  		return [-opp, -adj];
  	}

  	if (azim >= 270 && azim < 360) {
  		return [-adj, opp];
  	}

  	return [0, 0]
}