 would have been "up". If the units attribute value is a valid pressure unit the default value of the <cite>positive</cite> attribute is "down".</p>
<p>A vertical coordinate variable will be identifiable by</p>
<ul><li>units of pressure; or</li>
<li>the presence of the <cite>positive</cite> attribute with a value of "up"or "down" (case insensitive).</li>
</ul><p><strong>Latitude dimension:</strong><br />
Coordinate variables representing latitudes must always explicitly include the units attribute; there is