TA Engineering (General). Civil engineering (General) 10 TJ Mechanical engineering and machinery 9 NA Architecture 4 G70.39-70.6 Remote sensing 3 HD Industries. Land use. Labor 3 TH Building construction 3 G Geography (General) 2 G70.212-70.215 Geographic information system 2 GA Mathematical geography. Cartography 2 QA Mathematics 2 T Technology (General) 2 TL Motor vehicles. Aeronautics. Astronautics 2 TS Manufactures 2 Unspecified 2 G109.5 Global Positioning System 1 HE Transportation and Communications 1 QA76 Computer software 1 QC Physics 1 QH Natural history 1 TC Hydraulic engineering. Ocean engineering 1 TH434-437 Quantity surveying 1 TK Electrical engineering. Electronics Nuclear engineering 1 TP Chemical technology 1