XCORR(1)

💖 XCORR(1) 💖

okay bestie, welcome to the User Commands section of the manual, section 1 — and this one is called xcorr. it's giving "I compute cross-correlations and I'm not sorry about it" 💅

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🌸 NAME 🌸

xcorr — literally xcorr. that's it. that's the name. short, iconic, no notes ✨

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✨ SYNOPSIS ✨

xcorr master.PRM aligned.PRM [-time] [-real] [-freq] [-nx n] [-ny n] [-xsearch xs] [-ysearch ys]

like… you give it two PRM files and then sprinkle whatever flags your heart desires 🫶

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🦋 DESCRIPTION 🦋

so this program is part of GMTSAR, okay? and here's the whole vibe in one line, exactly as the manpage says it:

xcorr [GMTSAR] - Compute 2-D cross-correlation of two images

two images, 2-D cross-correlation, that's the whole plot. no cap 🔥

the two files you're handing over 🎀

• master.PRM — the PRM file for the reference image.
• aligned.PRM — the PRM file of the secondary image.

the flags, bestie (yes, all of them) 💅

• -time — use time cross-correlation.
• -freq — use frequency cross-correlation. this is the default, so if you say nothing, this is what you get.
• -real — read float numbers instead of complex numbers.
• -noshift — ignore ashift and rshift in the prm file (it sets them to 0).
• -nx nx — number of locations in the x (range) direction, as an int.
• -ny ny — number of locations in the y (azimuth) direction, as an int.
• -nointerp — do not interpolate the correlation function.
• -range_interp ri — interpolate range by ri (a power of two). [default: 2]
• -norange — do not range interpolate.
• -xsearch xs — search window size in the x (range) direction. int power of 2: [32 64 128 256]
• -ysearch ys — search window size in the y (azimuth) direction. int power of 2: [32 64 128 256]
• -interp factor — interpolate the correlation function by factor (an int). [default, 16]
• -v — verbose output, and it writes:
  • freq_xcorr.dat (the default)
  • time_xcorr.dat (if you used the -time option)

output tea ☕

use fitoffset.csh to convert the output to PRM format. iykyk ✨

examples (copy these fr fr) 🍓

xcorr IMG-HH-ALPSRP075880660-H1.0__A.PRM IMG-HH-ALPSRP129560660-H1.0__A.PRM -nx 20 -ny 50

xcorr file1.grd file2.grd -nx 20 -ny 50

the second one takes grids with real numbers, just so you know 👑

and then the manpage just… says it all again 🙈

for real, here's the Usage line, once more with feeling:

xcorr master.PRM aligned.PRM [-time] [-real] [-freq] [-nx n] [-ny n] [-xsearch xs] [-ysearch ys]

• master.PRM — PRM file for reference image
• aligned.PRM — PRM file of secondary image
• -time — use time cross-correlation
• -freq — use frequency cross-correlation (default)
• -real — read float numbers instead of complex numbers
• -noshift — ignore ashift and rshift in prm file (set to 0)
• -nx nx — number of locations in x (range) direction (int)
• -ny ny — number of locations in y (azimuth) direction (int)
• -nointerp — do not interpolate correlation function
• -range_interp ri — interpolate range by ri (power of two) [default: 2]
• -norange — do not range interpolate
• -xsearch xs — search window size in x (range) direction (int power of 2 [32 64 128 256])
• -ysearch ys — search window size in y (azimuth) direction (int power of 2 [32 64 128 256])
• -interp factor — interpolate correlation function by factor (int) [default, 16]
• -v — verbose output: freq_xcorr.dat (default), time_xcorr.dat (if -time option)
• use fitoffset.csh to convert output to PRM format
• Example: xcorr IMG-HH-ALPSRP075880660-H1.0__A.PRM IMG-HH-ALPSRP129560660-H1.0__A.PRM -nx 20 -ny 50
• Example: xcorr file1.grd file2.grd -nx 20 -ny 50 (takes grids with real numbers)

like okay repetitive queen, we hear you 🌈

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this page is xcorr, describing xcorr [GMTSAR] - Compute ..., dated May 2024, living in section XCORR(1). that's the sign-off bestie, mwah 💖✨🎀🦋