Re: Pseudogravity

Hi Lester,

Thank you for the feedback.  MagPick assumes extension .grd for GMT 3 grids
and extension .nc for GMT 4 and up. This might be a reason.

However I found some .nc files in the GMT distribution which are not 
readable
by magpick, so something to look into :)

Cheers,
Mikhail

On 02/04/2014 11:04 PM, Lester Anderson wrote:
> Hi Mikhail,
>
> Thanks for the pointers.
>
> The software did not recognise my GMT grids directly, and had to 
> convert to Surfer when loading: saving was fine to netCDF.
>
> I tried the pseudo gravity on a RTP grid (which was still Lat-Long), 
> and it seemed to work fine. The RTP grid was generated from the 
> grdredpol GMT function as I needed the differential RTP.
>
> I am assuming that a basic scripting function would be a 3 step process:
>
> 1. Reduce-to-pole (or equator if low magnetic latitide) GRDREDPOL
> 2. vertical integration GRDFFT
> 3. Applying a scaling function (a constant or differential value over 
> a large area ?) - GRDMATH -
>
> Currently, with GMT5, we can do the RTP (via grdredpol), but not the 
> RTE explicitly. Although I need to see what happens with a magnetic 
> dataset that is low lat in grdredpol
>
> Certainly, for a localised are Magpick works fine.
>
> Cheers
>
> Lester
>
> ------------------------------------------------------------------------
> Date: Tue, 4 Feb 2014 10:29:27 -0800
> From: [email protected]
> Subject: Re: [GMT-HELP] Pseudogravity
> To: [email protected]
>
> Hi Lester,
>
> I am pretty sure it can be done with GMT, but some scripting 
> programming could be required.
> If you want command-line solution to process bulk amount of data it is 
> certainly way to go.
>
> The other  answer might be off the list, but there is "magpick" 
> program available
> from
> http://www.geometrics.com/geometrics-products/geometrics-magnetometers/download-magnetometer-software/
>
> direct download link:
>
> ftp://geom.geometrics.com/pub/mag/Software/magpick-latest.exe
>
> MagPick can load / save GMT grid NC files.  It also has all potential 
> fields
> transformations implemented, such as reduction to the pole, analytic 
> signal,
> pseudo gravity etc.
> There are some limitations however:
>
> 1. Grids must be projected (not Lat/Lon grids)
> 2. There should be no gaps in the grid.  This could be circumvented by 
> making
> transformation and clipping grid after.
>
> There is also Linux version with the same functionality, not widely used.
> Let me know if you are interested in Linux.
>
> I hope it helps,
>
> Best Regards
> Mikhail Tchernychev
>
>
>
> On 2/4/2014 1:21 AM, Lester Anderson wrote:
>
>     Hello,
>
>     Is there a way to get the pseudogravity from magnetics using GMT
>     yet? I have not spotted that option in any of the obvious functions.
>
>     Cheers
>
>     Lester
>     To unsubscribe, send the message "signoff gmt-help" to
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>
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PLEASE NOTE: This message, including any attachments, may include privileged,
confidential and/or inside information. Any dissemination, distribution or copy
of this communication by   anyone other than the intended recipient is strictly
prohibited. If you are not the intended recipient, please notify the sender by
replying to this message and then delete it from your system. Information
provided via electronic media is not guaranteed against defects including
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