private String getPolePassed(final SatPos prevPos, final SatPos satPos) {
		String polePassed = DEADSPOT_NONE;

		final double az1 = prevPos.getAzimuth() / TWOPI * 360.0;
		final double az2 = satPos.getAzimuth() / TWOPI * 360.0;

		if (az1 > az2) {
			// we may be moving from 350 or greateer thru north
			if (az1 > 350 && az2 < 10) {
				polePassed = NORTH;
			} else {
				// we may be moving from 190 or greateer thru south
				if (az1 > 180 && az2 < 180) {
					polePassed = SOUTH;
				}
			}
		} else {
			// we may be moving from 10 or less through north
			if (az1 < 10 && az2 > 350) {
				polePassed = NORTH;
			} else {
				// we may be moving from 170 or more through south
				if (az1 < 180 && az2 > 180) {
					polePassed = SOUTH;
				}
			}
		}

		return polePassed;
	}