getpixscale | R Documentation |
Given a FITSio
of astro
header, calculate the image pixel scale.
getpixscale(header, CD1_1 = 1, CD1_2 = 0, CD2_1 = 0, CD2_2 = 1)
header |
Full FITS header in table or vector format. Legal table format headers are provided by the |
CD1_1 |
FITS header CD1_1 for the Tan Gnomonic projection system. Change in RA-Tan in degrees along x-Axis. |
CD1_2 |
FITS header CD1_2 for the Tan Gnomonic projection system. Change in RA-Tan in degrees along y-Axis. |
CD2_1 |
FITS header CD2_1 for the Tan Gnomonic projection system. Change in Dec-Tan in degrees along x-Axis. |
CD2_2 |
FITS header CD2_2 for the Tan Gnomonic projection system. Change in Dec-Tan in degrees along y-Axis. |
In most cases users will simply provide a valid header to find the WCS, but you can enter the CD values explicitly. Calculating the pixel scale from the latter is almost trivial, but the option is there for the curious/lazy.
Numeric scalar; the image pixscale in asec/pixel (so typically a value of 0.1-0.5 for modern survey instruments).
Aaron Robotham
## Not run:
#The answer should be almost exactly 0.2 asec/pixel:
#Using FITSio and ProFit packages
image = readFITS(system.file("extdata", 'KiDS/G266035fitim.fits', package="ProFit"))
getpixscale(image$hdr)
#Using astro package
image = read.fits(system.file("extdata", 'KiDS/G266035fitim.fits', package="ProFit"))
getpixscale(image$hdr[[1]])
## End(Not run)
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