objects rotation

This forum is dedicated to discuss all problems and suggestions related to the use of geopsy database and its plugins (array processing, H/V,...).
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luigiV
Posts: 121
Joined: Fri Jul 17, 2020 9:28 am

objects rotation

Post by luigiV »

Hi Marc,
is it possible to rotate the objects?
For example if in H/V rotate I wanted to put the frequency on the y axis how could I do it?

Thanks

Luigi
admin
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Posts: 841
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Location: ISTerre
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Re: objects rotation

Post by admin »

Hi Luigi,

This option is not currently available. All layers that show graphics are hardly linked to their X and Y. Being able to exchange the role of X and Y would imply a soft link at some point between data and screen plots. The transformation of coordinates is executed billions of times and adding a simple test to check how X and Y are mapped would lead to a tiny additional delay, but multiplied it can be no so tiny. These words are for plots managed by the applications: you would want to see updates of the rotated plots.

A more basic way to implement it would be to add a function to swap the properties of X and Y axes and the data plot. This way there is no issue regarding display efficiency but it is more static. It can be done only to unmanaged plots, copied in figue for instance.

A third way without adding any new implementation consists in exporting the grid data of H/V rotate results. The file is a text file with three columns: X, Y and value. Swap X and Y columns, For example, awk does it easily (no available in GeopsyLand). Under windows, the terminal provided by package git provides a decent bash terminal with awk.

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cat grid.file | awk '{if($1=="x") print else print $2,$1,$3}' > grid-swaped.file
Use this swapped file to create a new plot in figue. Fine in GeopsyLand.

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cat grid-swaped.file | figue -g
Copying properties from the original plot is not straight forward because axes are swapped.
Koen Van Noten
Posts: 4
Joined: Fri Nov 20, 2020 4:58 pm

Re: objects rotation

Post by Koen Van Noten »

Hi Luigi,

I find the HV rotate graph difficult to interpret in this X-Y (or Y-X as you want) linear format. If you're interested, I made a python script to replot the .grid rotate files into a 360° polar plot which makes it much more intuitive to interpret the data. The code also grabs the min/max amplitude at the min/max azimuth around f0.

The process is explained here:
Van Noten, K., Lecocq, T., Goffin, C., Meyvis, B., Molron, J., Debacker, T. & Devleeschouwer, X. 2022. Brussels’ bedrock paleorelief from borehole-controlled powerlaws linking polarised H/V resonance frequencies and sediment thickness. Journal of Seismology. https://doi.org/10.1007/s10950-021-10039-8

The Github code accompanying the paper is available here: https://github.com/KoenVanNoten/HVSR_to ... l_borehole

Check the HVSR polarisation.py script.

Hope it helps.
Cheers
Koen Van Noten
Royal Observatory of Belgium
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