如何轉換並保存healpy地圖到不同的座標系？

Question

我有一個與銀河座標healpix地圖。我想將該地圖轉換爲赤道座標系。我知道我可以使用mollview（）函數在赤道座標上繪製地圖。你有什麼辦法來保存這種轉換後的地圖嗎？

由於 Vinu

Answer 1

下面的函數改變地圖的座標系統。

def change_coord(m, coord): 
    """ Change coordinates of a HEALPIX map 

    Parameters 
    ---------- 
    m : map or array of maps 
     map(s) to be rotated 
    coord : sequence of two character 
     First character is the coordinate system of m, second character 
     is the coordinate system of the output map. As in HEALPIX, allowed 
     coordinate systems are 'G' (galactic), 'E' (ecliptic) or 'C' (equatorial) 

    Example 
    ------- 
    The following rotate m from galactic to equatorial coordinates. 
    Notice that m can contain both temperature and polarization. 
    >>>> change_coord(m, ['G', 'C'] 
    """ 
    # Basic HEALPix parameters 
    npix = m.shape[-1] 
    nside = hp.npix2nside(npix) 
    ang = hp.pix2ang(nside, np.arange(npix)) 

    # Select the coordinate transformation 
    rot = hp.Rotator(coord=reversed(coord)) 

    # Convert the coordinates 
    new_ang = rot(*ang) 
    new_pix = hp.ang2pix(nside, *new_ang) 

    return m[..., new_pix] 

的例子是你的情況