Note

This page was generated from examples/notebooks/ellipses.ipynb.

Ellipses

%matplotlib widget
import starepandas
import pystare
import matplotlib.pyplot as plt
import geopandas
import copy
import numpy
import pandas

mod03_name = '../tests/data/granules/MOD03.A2017345.1925.006.2017346004924.hdf'
mod03 = starepandas.read_granule(mod03_name, sidecar_path='../tests/data/granules/MOD03.A2017345.1925.006.2017347015352_stare.nc', sidecar=True, xy=True)

mod03_center = copy.copy(mod03[630:634])
mod03 = copy.copy(mod03[0:4])

lat, lon = pystare.to_latlon(mod03.sids)
lon = lon - 360
geoms = geopandas.points_from_xy(x=lon,y=lat, crs=4326)
mod03.set_geometry(geoms, inplace=True)

lat, lon = pystare.to_latlon(mod03_center.sids)
lon = lon - 360
geoms = geopandas.points_from_xy(x=lon,y=lat, crs=4326)
mod03_center.set_geometry(geoms, inplace=True)

Make ellipses

ellipse_sids = starepandas.io.granules.modis.make_ellipse_sids(mod03, n_partitions=1, num_workers=1, level=17, crs=3857, modis_resolution=1000)
mod03['ellipse_sids'] = ellipse_sids

ellipse_trixels = mod03.make_trixels(sid_column='ellipse_sids', n_partitions=1, num_workers=1)
mod03['ellipse_trixels'] = ellipse_trixels

ellipse_sids = starepandas.io.granules.modis.make_ellipse_sids(mod03_center, n_partitions=1, num_workers=1, level=17, crs=3857, modis_resolution=1000)
mod03_center['ellipse_sids'] = ellipse_sids

ellipse_trixels = mod03_center.make_trixels(sid_column='ellipse_sids', n_partitions=1, num_workers=1)
mod03_center['ellipse_trixels'] = ellipse_trixels

Make circles

r_circle = 500
r_earth = 6378137
phi = r_circle /2/3.14/r_earth*360
phi

0.004493854613371522

circle_sids = starepandas.make_circular_sids(mod03, level=17, diameter=phi, n_partitions=1, num_workers=1)
mod03['circle_sids'] = circle_sids

cirlce_trixels = mod03.make_trixels(sid_column='circle_sids', n_partitions=1, num_workers=1)
mod03['circle_trixels'] = cirlce_trixels

circle_sids = starepandas.make_circular_sids(mod03_center, level=17, diameter=phi, n_partitions=1, num_workers=1)
mod03_center['circle_sids'] = circle_sids

cirlce_trixels = mod03_center.make_trixels(sid_column='circle_sids', n_partitions=1, num_workers=1)
mod03_center['circle_trixels'] = cirlce_trixels

Plot

-140.4 +140.05

-0.3499999999999943

-124.85+124.55

-0.29999999999999716

fig, ax = plt.subplots(2, 1, figsize=(10,3), dpi=180)

mod03.set_trixels('ellipse_trixels').plot(ax=ax[0], trixels=True, boundary=True, color='blue', legend=True, linewidth=0.1, zorder=2)
mod03.set_trixels('circle_trixels').plot(ax=ax[0], trixels=True, boundary=True,  linewidth=0.1, zorder=2, color='green')
mod03.plot(ax=ax[0], trixels=False, markersize=3, marker='.', zorder=1, color='red')
ax[0].set_xlim(-140.4, -140.05)

mod03_center.set_trixels('ellipse_trixels').plot(ax=ax[1], trixels=True, boundary=True, color='blue', legend=True, linewidth=0.1, zorder=2)
mod03_center.set_trixels('circle_trixels').plot(ax=ax[1], trixels=True, boundary=True,  linewidth=0.1, zorder=2, color='green')
mod03_center.plot(ax=ax[1], trixels=False, markersize=3, marker='.', zorder=1, color='red')
ax[1].set_xlim(-124.80,-124.45)


fig.tight_layout()

Fit Ellipse

deg = [0.,10,20,30,40,50,55]
scan_pts = [1, 1.05, 1.2, 1.5, 2, 3.2, 4.83]
trac_pts = [1, 1.028, 1.083, 1.193, 1.367, 1.688, 2.01]

def func(x, a, b, c):
    return numpy.exp(a*x)/b+c

from scipy.optimize import curve_fit
scan_params, cov = curve_fit(func, deg, scan_pts, bounds=(0, [1, 100, 1]))
trac_params, cov = curve_fit(func, deg, trac_pts, bounds=(0, [1, 100, 1]))

fig, ax = plt.subplots(figsize=(9,5), dpi=200)

df = pandas.DataFrame({'deg': deg, 'scan_pts': scan_pts, 'trac_pts': trac_pts})
df['Along scan iFOV size'] = numpy.exp(scan_params[0]*df['deg'])/scan_params[1]+scan_params[2]
df['Along track iFOV size'] = numpy.exp(trac_params[0]*df['deg'])/trac_params[1]+trac_params[2]

#df.plot(ax=ax, x='deg', y=['scan_pts', 'trac_pts'], grid=True, ylabel='Distance', xlabel='Scan Angle', marker='x', linewidth=0)
df.plot(ax=ax, x='deg', y=['Along scan iFOV size', 'Along track iFOV size'], grid=True, ylabel='Distance in km', xlabel='Scan Angle')
fig.tight_layout()