gloc_subj_tab updated=20050803 uc=2 tc=2 lc=0 bc=3:3 Class|Subject|Notes gloc|altitude|Altitude is measured as height above mean sea level (MSL), although there are various models for MSL. Negative if below MSL. gloc|latitude|Latitude is measured as positive north of the Equator, negative south of the Equator. Range: -90 to +90. gloc|longitude|Longitude is measured as east longitude; west longitude can be expressed as negative numbers. Range is either 0 to 360, or -180 to +180. gloc|time|Time of an observation, or applicable time of an integrated measurement or grab sample. gloc|launch time|Launch time of an aircraft or sounding platform (balloon, rocket, dropsonde, etc.). gloc|sample start time|Start time of a grab sample or integrated measurement. Requires an associated stop time. gloc|sample stop time|Stop time of a grab sample or integrated measurement. Requires an associated start time.