Hi, I've some problem with the declination. For the coordinate UTM31 398980 4969737 in the log file there is: output coordinate system: UTM31 meridian convergence (deg): 0.9024 geomag declinations (deg): 2007.1.1 -0.7738 2008.1.1 -0.6570 The coordinate UTM31 398980 4969737 are equal to N 44°52'26" E 1°43'15" rapport to greenwich meridian. If I go on this site: http://www.ngdc.noaa.gov/seg/geomag/jsp/IGRFWMM.jsp it gives me for 2007.1.1 a declination of -0°50' so -0.83°. This value is different in relation to the therion one. If I try with declimag (http://vtopo.free.fr) it gives me a value as with http://www.ngdc.noaa.gov/seg/geomag/jsp/IGRFWMM.jsp Another quetion: in my centreline there is a line: date 2007.09.08 Why this date is not used for the declination? Best regards, -- +--------------------------------------------------------------+ | Gaëtan PERRIER Nyctalopes Ambidextres & TRIAS | | gaetan.perrier@speleolot.org http://www.speleolot.org/ | +--------------------------------------------------------------+