Topcon описание формата tvf

Код:

GPS Vector files have the following format:
Header(//Topcon Vector Format:v.number of the version,linear units,)
VPP(for vector),Name_Point1,Name_Point2,dX,dY,dZ,sigma_dX,sigma_dY,sigma_dZ,cor_XY,cor_XZ,cor_YZ,
P(for point),Nane_Point,Lat(DD MMSS.ss),Lon(DD MMSS.ss),Ell.Height,Code,Note,
//TopconVectorFormat:v.1,Meters,
VPP,1,2,2.4498,2.7704,-3.2041,0.00131407,0.00106341,0.00257335,0.2479,0.5525,0.2098
VPP,1,3,0.3370,3.5418,-3.8074,0.00154384,0.00201876,0.00239150,0.4817,0.4323,0.4580
VPP,2,3,-2.1339,0.7589,-0.6185,0.00315621,0.00445358,0.00476713,0.4766,0.3580,0.4004
VPP,1,4,2.9617,1.0948,-4.1492,0.00743030,0.00466686,0.00739715,0.2438,0.1733,0.3977
VPP,2,4,0.5134,-1.6737,-0.9458,0.00467626,0.00271100,0.00492552,0.2998,0.1997,0.3185
VPP,3,4,2.6111,-2.4383,-0.3702,0.01177912,0.00991061,0.01118924,0.6141,0.4192,0.4301
P,1,55 33 45.60559,37 58 40.69849,147.849,Hiper XT,Base_St
P,2,55 33 45.44999,37 58 40.73705,147.266,,
P,3,55 33 45.47084,37 58 40.84595,146.087,,Left_C 
P,4,55 33 45.44942,37 58 40.64386,146.128,Legant E,Right_C

Что такое sigma_ и cor_???