Figure: Radio Interferometry Schematic

figures/radio_interferometry/.gitignore

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+rit_schematic_*.*

figures/radio_interferometry/Makefile

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+SUBDIRS := $(subst Makefile,,$(wildcard */Makefile))
+
+.PHONY: all dist dist-clean $(SUBDIRS)
+
+all: dist $(SUBDIRS)
+
+dist: dist.png dist.pdf
+	#
+
+.PHONY: dist.png
+dist.png: \
+	rit_schematic_base.png \
+	rit_schematic_true.png \
+	rit_schematic_close.png \
+	rit_schematic_far.png \
+	#
+
+.PHONY: dist.pdf
+dist.pdf: \
+	rit_schematic_base.pdf \
+	rit_schematic_true.pdf \
+	rit_schematic_close.pdf \
+	rit_schematic_far.pdf \
+	#
+
+$(SUBDIRS):
+	@$(MAKE) -C $@
+
+dist-clean:
+	rm -v rit_schematic_*
+
+rit_schematic_base.%: src/rit_scheme.py
+	$< 'base' $@
+
+rit_schematic_true.%: src/rit_scheme.py
+	$< 'true' $@
+
+rit_schematic_close.%: src/rit_scheme.py
+	$< 'closeby' $@
+
+rit_schematic_far.%: src/rit_scheme.py
+	$< 'far-away' $@

figures/radio_interferometry/src/rit_scheme.py

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+#!/usr/bin/env python3
+
+__doc__ = \
+"""
+Show geometry and time delay between radio antennas 
+and a source (true, and expected).
+"""
+
+import matplotlib.pyplot as plt
+from matplotlib.path import Path
+import matplotlib.patches as patches
+
+import numpy as np
+
+def antenna_path(loc, size=1, height=(.5)**(.5), width=1, stem_height=None):
+    stem_height = stem_height if stem_height is not None else height
+
+    vertices = [
+        (0, 0), # center, middle
+        ( width/2*size,  height/2*size), #right, top
+        ( width/2*size, -height/2*size), #right, bottom
+        (-width/2*size,  height/2*size), #left, top
+        (-width/2*size, -height/2*size), #left, bottom
+        (0, 0), # back to center
+        (0, -stem_height), # stem
+        (0, 0), # back to center
+    ]
+
+    codes = [
+            Path.MOVETO,
+            Path.LINETO,
+            Path.LINETO,
+            Path.LINETO,
+            Path.LINETO,
+            Path.LINETO,
+            Path.LINETO,
+            Path.CLOSEPOLY,
+    ]
+
+    # modify vertices
+    for i, v in enumerate(vertices):
+        vertices[i] = ( loc[0] + v[0], loc[1] + v[1] )
+
+    return Path(vertices, codes)
+
+
+def radio_interferometry_figure(emit_loc=(3,8), resolve_loc=None, N_antenna=4, ant_size=0.5, **fig_kwargs):
+    fig, ax = plt.subplots(**fig_kwargs)
+
+    annot_kwargs = dict(
+            color='red',
+            fontsize=15,
+    )
+
+    ray_kwargs = dict(
+            marker=None,
+            ls='solid',
+            color='red',
+            alpha=0.8
+    )
+    antenna_patch_kwargs = dict(
+            edgecolor='k',
+            facecolor='none',
+            lw=2
+    )
+
+    antenna_patches = []
+    dx_antenna = 1.5
+    stem_height = ant_size
+    for i in range(N_antenna):
+        path = antenna_path( (4+dx_antenna*i, stem_height), size=ant_size, stem_height=stem_height)
+        patch = patches.PathPatch(path, **antenna_patch_kwargs)
+        ax.add_patch(patch)
+        antenna_patches.append(patch)
+
+        if i == N_antenna - 1:
+            ant_loc = path.vertices[0]
+            ax.annotate("$\\vec{a_i}$", (ant_loc[0]+0.4, 0.8), va='top', ha='left', **{**annot_kwargs, **dict(color='k')})
+
+    # ground level
+    ax.axhline(0, color='k')
+
+    # indicate antenna signal
+    ant_loc = antenna_patches[int(2/4*N_antenna)].get_path().vertices[0]
+    ax.annotate("$S_i(t)$", (ant_loc[0], ant_loc[1]-stem_height-0.2), va='top', ha='center', **annot_kwargs)
+
+
+    if emit_loc or resolve_loc:
+        # resolve_loc
+        if resolve_loc is None:
+            resolve_loc = emit_loc
+
+        if resolve_loc:
+            for i, antenna in enumerate(antenna_patches):
+                    ant_loc = antenna.get_path().vertices[0]
+
+                    # rays from the antenna to resolve_loc
+                    ax.plot( (ant_loc[0], resolve_loc[0]), (ant_loc[1], resolve_loc[1]), **ray_kwargs)
+                    if i == N_antenna - 1:
+                        ax.annotate("$\Delta_i$", ( (ant_loc[0]+resolve_loc[0])/2, (ant_loc[1]+resolve_loc[1])/2 ), va='bottom', ha='left', **annot_kwargs)
+
+            ax.plot(*resolve_loc, 'ro')
+            ax.annotate("$S(\\vec{x}, t)$", resolve_loc, ha='left', va='bottom', **annot_kwargs)
+
+        # emit loc
+        if emit_loc:
+            ax.plot(*emit_loc, 'ko')
+
+            ax.annotate('$S_0$', emit_loc, ha='right', va='top', **{**annot_kwargs, **dict(color='k')})
+
+    ax.set_xlim(-1, 10)
+    ax.set_ylim(-1, 10)
+
+    ax.axis('off')
+
+    fig.tight_layout()
+
+    return fig
+
+
+if __name__ == "__main__":
+    emit_loc = (2.5, 8)
+    figsize = (6,6)
+
+    from argparse import ArgumentParser
+    import os.path as path
+
+    parser = ArgumentParser(description=__doc__)
+    parser.add_argument('scenario', choices=['base', 'true', 'closeby', 'far-away'], default='true')
+    parser.add_argument("fname", metavar="path/to/figure[/]", nargs="?", help="Location for generated figure, will append __file__ if a directory. If not supplied, figure is shown.")
+
+    args = parser.parse_args()
+
+    if args.fname is not None and path.isdir(args.fname):
+        args.fname = path.join(args.fname, path.splitext(path.basename(__file__))[0] + ".pdf")
+
+    ###
+    emit_loc = None
+    resolve_loc = None
+    if args.scenario != 'base':
+        emit_loc = (2.5, 8)
+
+        if args.scenario == 'closeby':
+            resolve_loc = (3, 8)
+        elif args.scenario == 'far-away':
+            resolve_loc = (8, 8)
+    
+    fig = radio_interferometry_figure(emit_loc=emit_loc, resolve_loc=resolve_loc, figsize=figsize)
+
+    if args.fname is not None:
+        plt.savefig(args.fname)
+    else:
+        plt.show()