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This notebook can be used to see how the functionality to deal with Healpix Tiles can be used. More specifically, this notebook shows

How to obtain points on the edges of Healpixels and demonstrate that this matches Healpy drawings
How to draw Healpixels on a basemap plot



In [1]:

    
from opsimsummary import healpix_boundaries



In [2]:

    
import numpy as np



In [3]:

    
import healpy as hp



In [4]:

    
%matplotlib inline

Demo showing that a healpy mollview plot matches points claimed as boundaries



In [5]:

    
ipix  = np.array([11])



In [6]:

    
lon, lat = healpix_boundaries(ipix, nside=4, units='radians', nest=True, step=2)

The return of this funciton is a tuple of lon and lat



In [7]:

    
arr = np.ones(hp.nside2npix(4)) * hp.UNSEEN
arr[ipix] = 1
hp.mollview(arr, nest=True)
hp.projscatter(lat, lon)









    Out[7]:





<matplotlib.collections.PathCollection at 0x108aaea10>

How to get more points?



In [8]:

    
lon, lat = healpix_boundaries(ipix, nside=4, units='radians', nest=True, step=3)



In [9]:

    
arr = np.ones(hp.nside2npix(4)) * hp.UNSEEN
arr[ipix] = 1
hp.mollview(arr, nest=True)
hp.projscatter(lat, lon)









    Out[9]:





<matplotlib.collections.PathCollection at 0x109a7ccd0>



In [10]:

    
lon









    Out[10]:





array([ 0.        ,  0.        ,  0.        ,  0.        ,  0.15707963,
        0.28559933,  0.39269908,  0.428399  ,  0.4712389 ,  0.52359878,
        0.39269908,  0.22439948])

Draw a Healpix in basemap



In [11]:

    
from opsimsummary import HPTileVis, HealpixTiles



In [12]:

    
hptiles = HealpixTiles(preComputedMap='/Users/rbiswas/data/LSST/OpSimData/healpixelized_MINION_1016_256_64_indexed.db',
                       nside=256)



In [13]:

    
hptvis = HPTileVis(hptiles, None)



In [31]:

    
fig, tile_center, _  = hptvis.plotTilePointings((552466), projection='cea', paddingFactors=0.5, ax=None,drawPointings=False
                        ,
                                       **dict(fill=False, color='g', alpha=0.01)
                         )



In [30]:

    
hp.get_all_neighbours(256,theta=552466, nest=True)









    Out[30]:





array([552455, 552461, 552472, 552473, 552467, 552465, 552464, 552453])



In [32]:

    
for ipix in hp.get_all_neighbours(256, theta=552466, nest=True):
    _, _, _ = hptvis.plotTilePointings(ipix, tile_centers=tile_center, projection='cea', paddingFactors=0.5, ax=fig.axes[0],drawPointings=False
                        ,
                                       **dict(fill=False, color='g', alpha=0.01)
                         )



In [33]:

    
fig









    Out[33]: