Extract High Frequency Noise

DavidDeCastro

How can I attenuate high frequency noise from airborne magnetic data, which are supposed microlevelled?
The fly lines are E-W and spaced ~500m

BeckyBodger

Hi @DavidDeCastro, if you have the database and if you doubt the data was microlevelled, you could try to microlevel the data yourself using the Microlevelling tools under the Geophysical Levelling Extension.

There is a description of what to do in the help files:

https://my.geosoft.com/supportcentre#/help/oasismontaj-extensions-decorr_gx.htm
https://my.geosoft.com/supportcentre#/help/oasismontaj-extensions-miclev_gx.htm

1. Calculate the noise grid:
Microlevelling > Extract Noise
For decorrugation cutoff wavelength enter 4 times the flight line spacing.

2. Microlevel (subtract noise from original):
Microlevelling > Microlevel
Populates fields automatically if you ran the Extract Noise tool.

If that doesn't work and you are using a current subscription I would recommend emailing support@Geosoft.com and sending us your grid to investigate further.

DavidDeCastro

Thank you!

ElizabethBaranyi

David, looks like you have the GDB. In this case apply the non-linear filter to the mag data in the GDB. Adjust your filter width so that it just takes out the systematic noise without altering the nature of the real data, finally grid the filtered profile data.