Overplotting

Here is an example on how to overplot multiple map layers with the OMEGA-Py display functions. In this example will plot a 1.5μm band depth map over a reflectance background to highlight the areas covered by water ice.

In the following, we assume that we have already loaded the module and a corrected OMEGA observation as follows:

import omegapy.omega_data as od
import omegapy.omega_plots as op

Also let's assume that you have completed step 1 to 3 of the band depth example to process the OMEGA data cube ORB0979_2 and compute its 1.5μm band depth map.

Quick reminder

omega = od.autoload_omega('0972_2')

bd_15 = od.BD_omega(omega, [1.5, 1.51], 1.30, 1.71, norm=True)

Step 1 – Define the additional layers

Let's say that you want to show the pixels cover with water ice, that we will define as pixels with a 1.5μm BD > 10%. We will create a mask to hide the pixels with no water ice / lower BD:

import numpy as np

mask_bd15 = np.ones(bd_15.shape)    # Initialisation with array of 1
mask_bd15[bd_15 < 0.1] = np.nan     # NaN for the pixels with no ice that we want to hide

Step 2 – Display the figure

Important

The important point here is to select the same figure for all the plots, which is handled by the Nfig argument.

Plot the background

For the background map, we plot the reflectance at 1.085 μm with show_omega_v2.

We hide the colorbar with cbar = False here to only have the one associated with the BD map.

op.show_omega_v2(
    omega,
    lam = 1.085,
    polar = True,
    vmin = 0,
    vmax = 0.5,
    cbar = False,   # We don't want to display the colorbar for the reflectance background
    Nfig = 1,       # int or str
    )

Plot the BD layer

Then we plot the 1.5 μm BD with show_data_v2 on the same figure, using the mask to hide the pixels of the BD map without water ice signature.

import cmocean.cm as cmo

op.show_data_v2(
    omega,
    data = bd_15,
    mask = mask_bd15,
    polar = True,
    cmap = cmo.ice,
    cb_title = "1.5 μm BD",
    vmin = 0,
    vmax = 0.75,
    Nfig = 1,       # int or str - same as for the background
    )

Transparent overlays

One can also use the alpha keyword of the show_data_v2 function to set the transparency of the different overlays, in addition or instead of using a mask.

Overplot1.5μm Band DepthSurface reflectance

ORB0979_2 1.5μm BD on reflectance – Polar projection

ORB0979_2 1.5μm BD – Polar projection

ORB0979_2 reflectance – Polar projection