// Javascript Pressure Conversion Routines
// Original Author Unknown
//
function decidePconvert(height, pressure) {
	height = parseFloat(document.Pconvert.Height.value);
	pressure = parseFloat(document.Pconvert.AltPress.value);
	var Mheight, MBpressure;

	if (document.Pconvert.heightunit[0].checked) {
		Mheight = parseFloat(convertfeettometer(height));
	}
                                
	if (document.Pconvert.heightunit[1].checked) {
		Mheight = height;
	}
                
	if (document.Pconvert.pressureunit[0].checked) {
		INpressure = pressure;
	}
                                
	if (document.Pconvert.pressureunit[1].checked) {
		INpressure = parseFloat(convertmmHGtoinHG(pressure));
	}
                                
	if (document.Pconvert.pressureunit[2].checked) {
		INpressure = parseFloat(convertmbtoinHG(pressure));
	}

	var stnpressure;                
	stnpressure = INpressure * Math.pow((288 - 0.0065 * Mheight)/288,5.2561)
	document.Pconvert.StationPressinHG.value = roundOff(stnpressure);
	document.Pconvert.StationPressmmHG.value =
		roundOff(parseFloat(convertinHGtommHG(stnpressure)));
	document.Pconvert.StationPressmb.value =
		roundOff(parseFloat(convertinHGtomb(stnpressure)));
}
                                
function convertinHGtomb(inHG) {
	var mb;
	mb = 33.8639*inHG;
	return mb;
}
function convertmbtoinHG(mb) {
	var inHG;
	inHG = 0.0295300*mb;
	return inHG;
}
function convertinHGtommHG(inHG) {
	var mmHG;
	mmHG = 25.4*inHG;
	return mmHG;
}
function convertmmHGtoinHG(mmHG) {
	var inHG;
	inHG = 0.03937008*mmHG;
	return inHG;
}
function convertfeettometer(feet) {
	var meter;
	meter = 0.3048 * feet;
	return meter;
}
function roundOff(value) {
	value = Math.round(100*value)/100;
	return value;
}
function setToNull() {
	document.Pconvert.StationPressinHG.value="";
	document.Pconvert.StationPressmmHG.value="";
	document.Pconvert.StationPressmb.value="";
	document.Pconvert.AltPress.value="";
	document.Pconvert.Height.value="";
}