Coordinate Transformations Module
Tamar Ervin
Date: June 24, 2021
Coordinate transformation functions to transform from the Helioprojective Cartesian to Heliographic Carrington Coordinates.
coordinates(smap)
calculate array of mu values and cartesian coordinates for image
Parameters
map
Sunpy map object
Returns
float, array
array of x coordinates in helioprojective cartesian system
float, array
array of y coordinates in helioprojective cartesian system
float, array
array of pixel distances
float, array
array of solar radius values
float
observer distance from sun in solar radii
float, array
array of mu values
fix_mu(mu, smaps, mu_cutoff=0.3)
function to remove pixel values where mu is less than a cutoff value
Parameters
float, array
cosine of the center to limb angle
map, list
list of Sunpy map object
float
minimum mu cutoff value
Returns
float, array
corrected cosine of the center to limb angle
map, list
corrected Sunpy map objects
get_map_scales(smap)
compute the solar X and solar Y 2D pixel scale arrays from a sunpy map object - If the image has been rotated to solar north up, then the x and y scales will be in the helioprojective cartesian system with units of [Rs].
Parameters
map
Sunpy map object
Returns
numpy array
array of x coordinates in helioprojective cartesian system
numpy array
array of y coordinates in helioprojective cartesian system
pix_area_hem(wij, nij, rij, smap)
calculate the area of each pixel in uHem for use in area thresholding for convective velocity and identification of solar regions
Parameters
float, array
array of pixel coordinates relative to solar center in westward direction
float, array
array of pixel coordinates relative to solar center in northward direction
float, array
array of pixel coordinates relative to solar center in radial direction
map
Sunpy map object
Returns
float, array
pixel areas in uHem
vel_coords(x, y, pd, r, smap)
calculate coordinate transformation to heliographic Carrington coordinates
Parameters
float, array
array of x coordinates in helioprojective cartesian system
float, array
array of y coordinates in helioprojective cartesian system
float, array
array of pixel distances
float, array
array of solar radius values
map
Sunpy map object
Returns
float, array
array of pixel coordinates relative to solar center in westward direction
float, array
array of pixel coordinates relative to solar center in northward direction
float, array
array of pixel coordinates relative to solar center in radial direction