I am currently a student in year 11 and have a chemistry assignment that i need some help with. Does anyone know how data/spectra is obtained, and how it is interpreted?
Is GC used as a qualitative or quantitative technique?
and information on the main use of GC in industry/forensic application

spectra data of a compound are gathered by sending certain wavelengths of electromagnetic radiation through the compound and the resulting absorption is measured. Certain wavelengths will be absorbed by certain chemical structures and are indicative of their presence. Thus if wavelengths that are absorbed by keto groups or by an aromatic ring are absorbed when sent through a compound it is assumed that these are present in the compound.
GC can be used as both qualitative and quantitative technique, but it is primarily quantitative in actual use.
GC is used in petroleum industry, chemical manufacturing, air and water monitoring (environmental) (safety) industries, health industries (hospitals, pharmaceutical manufacturing, drug testing), plastics, paint, energy, manufacturing research in manifold industries, and in outer space (analysis of Titan's atmosphere).
check the web for many good sites which discuss this science in detail and do a little research yourself.