Diagnosis is tricky without seeing the data, but here are a few tips. My apologies if you've already covered all of these or if they seem too basic. But if the directional filters you describe haven't solved the problem, it sounds to me like there may be a more fundamental issue.
First thing I always do is verify that it is actually a level problem and not a lag problem. Not sure if that translates to a ground survey based on stations, but perhaps double check the timing of your diurnal correction as well. Second is to check that it's not a heading error. Was the operator contaminated? Is there a systematic fix you can apply? Tie lines or microlevelling should have fixed this, but maybe not. Also check that your grid cell size isn't too small for the line spacing. Maybe tweaking some of the other gridding parameters will help. Then I'd look at your individual derivative maps (since they combine to produce the AS). Presumably your cross-line gradient has more problems than down-line. Does it suggest a deeper data problem? Can you filter just that directional gradient? Hope these suggestions help. ************* Jeff Gamey, Battelle, PG, PMP cell 865-599-0820 fax 614-458-0275 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of maduhu Sent: Monday, April 15, 2013 3:25 PM To: Geosoft Oasis montaj and Target Subject: [geonet] RE; filtering problem Hi I was doing ground magnetic survey, I have to filter the data before I produce TMI, Analytic signal and Derivative maps. I did microlevelling using Butterworth and Directional cosine filters but I still see line based noise especially wheny you want analytic signal map, any one to help me to eradicate the problem --- Forum archives can be accessed here: http://lyris.geosoft.com/read/?fourm=geonet You are currently subscribed to geonet as: [email protected]. To subscribe or unsubscribe from any of our forums, select the User Forum selection on the Geosoft Community page: http://www.geosoft.com/support/community --- Forum archives can be accessed here: http://lyris.geosoft.com/read/?fourm=geonet You are currently subscribed to geonet as: [email protected]. To subscribe or unsubscribe from any of our forums, select the User Forum selection on the Geosoft Community page: http://www.geosoft.com/support/community
