[SAC-HELP] finding difficulty in rotation

[kawsar laskar]

hello Sir,
I m an M.Tech student of computational seismology. I
am using SAC for receiver function analysis .I am
finding difficulty in performing rotation of NS and EW
component to radial and tangential components.
whenever I try the command "rot to gcp"an error
message telling both the components are not horizontal
comes.

what is the wrong with that.Is there anything wrong
with the command or data .what should I do now please advise.


		
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