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# Copyright (c) 2017 Weitian LI <weitian@aaronly.me>
# MIT license
"""
Radio interferometer layout configurations.
"""
import os
import logging
import shutil
import numpy as np
import pandas as pd
from .wgs84 import geodetic2enu
logger = logging.getLogger(__name__)
class SKA1Low:
"""
Process SKA1-low layout data and generate the telescope model
for OSKAR.
Parameters
----------
infile : str
Path to the SKA1-low layout data file
stn_antennas : int, optional
Number of antenna elements per station (default: 256)
stn_diameter : float, optional
Diameter of each station (unit: [m])
ant_min_sep : float, optional
Minimum separation between two antennas (unit: [m])
Reference
---------
[1] SKA-TEL-SKO-0000422, revision 02, 2016-05-31, Table 1
http://astronomers.skatelescope.org/wp-content/uploads/2016/09/SKA-TEL-SKO-0000422_02_SKA1_LowConfigurationCoordinates-1.pdf
[2] OSKAR: telescope model
http://www.oerc.ox.ac.uk/~ska/oskar2/OSKAR-Telescope-Model.pdf
"""
def __init__(self, infile, stn_antennas=256, stn_diameter=45.0,
ant_min_sep=1.5):
self.infile = infile
self.stn_antennas = stn_antennas
self.stn_diameter = stn_diameter
self.ant_min_sep = ant_min_sep
self.data = pd.read_csv(infile, sep="\s+", comment="#",
index_col="Label")
logger.info("Read telescope layout data from: %s" % infile)
self.position_wgs84 = np.array(self.data.loc["CENTER", :])
logger.info("Telescope center coordinate: (%f, %f)" %
tuple(self.position_wgs84))
self.labels = self.make_station_labels(self.data.index[1:])
# (longitudes, latitudes)
self.layouts_wgs84 = np.array(self.data.iloc[1:, :])
logger.info("Number of stations: %d" % len(self.layouts_wgs84))
def generate_stations(self):
"""
Generate the antenna elements layouts for each station.
"""
layouts = []
N = len(self.labels)
logger.info("Number of antennas per station: %d" %
self.stn_antennas)
logger.info("Station diameter: %.2f [m]" % self.stn_diameter)
logger.info("Station antennas minimum separation: %.2f [m]" %
self.ant_min_sep)
logger.info("Generating antenna elements layouts ...")
for i, label in enumerate(self.labels):
logger.debug("Generate layout for [#%d/%d] station: %s" %
(i+1, N, label))
x, y, __ = self.rand_uniform_2d(
n=self.stn_antennas, r_max=self.stn_diameter/2.0,
min_sep=self.ant_min_sep)
layouts.append((x, y))
self.stn_layouts = layouts
logger.info("DONE generate station layouts.")
def make_oskar_model(self, outdir, clobber=False):
"""
Create the telescope model for OSKAR.
"""
if os.path.exists(outdir):
if clobber:
shutil.rmtree(outdir)
logger.warning("Removed existing model: %s" % outdir)
else:
raise FileExistsError("Output directory already exists: " %
outdir)
os.mkdir(outdir)
logger.info("Created telescope model at: %s" % outdir)
# Write position
fposition = os.path.join(outdir, "position.txt")
open(fposition, "w").writelines([
"# SKA1-low layout: %s\n" % self.infile,
"# Telescope center position (WGS84)\n",
"# longitude[deg] latitude[deg]\n",
"%.8f %.8f\n" % tuple(self.position_wgs84)
])
logger.info("Wrote telescope position: %s" % fposition)
# Write layout of stations
p0 = [self.position_wgs84[0], self.position_wgs84[1], 0.0]
layouts = np.array([geodetic2enu((lon, lat, 0.0), p0)
for lon, lat in self.layouts_wgs84])
layouts[:, 2] = 0.0 # set `up` to 0.0
flayout = os.path.join(outdir, "layout.txt")
header = ["SKA1-low layout: %s" % self.infile,
"All stations layout",
"East[m] North[m] Up[m]"]
np.savetxt(flayout, layouts, header="\n".join(header))
logger.info("Wrote station layouts: %s" % flayout)
# Write stations
N = len(self.labels)
for i, label in enumerate(self.labels):
stn_dir = os.path.join(outdir, label)
os.mkdir(stn_dir)
fstation = os.path.join(stn_dir, "layout.txt")
header = [
"Antenna elements layout",
"Station label: %s" % label,
"Number of antennas: %d" % self.stn_antennas,
"Station diameter: %.2f [m]" % self.stn_diameter,
"Antenna minimum separation: %.2f [m]" % self.ant_min_sep,
"X[m] Y[m]"
]
np.savetxt(fstation, np.column_stack(self.stn_layouts[i]),
header="\n".join(header))
logger.debug("Wrote layout for [#%d/%d] station: %s" %
(i+1, N, fstation))
logger.info("DONE wrote telescope model: %s" % outdir)
@staticmethod
def make_station_labels(labels, base="stn"):
"""
Make the labels for each station, which will also be used
as the sub-directory names for the output telescope model.
"""
N = len(labels)
ndigits = int(np.log10(N)) + 1
fmt = "{base}.%(id)0{ndigits}d.%(label)s".format(
base=base, ndigits=ndigits)
stnlabels = [fmt % {"id": i+1, "label": l}
for i, l in enumerate(labels)]
return stnlabels
@staticmethod
def rand_uniform_2d(n, r_max, min_sep, r_min=None):
"""
Generate 2D random points with a minimum separation within
a radius range (i.e., annulus/circle).
Credit:
* https://github.com/OxfordSKA/SKA1-low-layouts :
layouts/utilities/layout.py - Layout.rand_uniform_2d()
"""
grid_size = min(100, int(np.ceil(r_max * 2.0) / min_sep))
grid_cell = r_max * 2.0 / grid_size
scale = 1.0 / grid_cell
x, y = np.zeros(n), np.zeros(n)
grid = {
"start": np.zeros((grid_size, grid_size), dtype=np.int),
"end": np.zeros((grid_size, grid_size), dtype=np.int),
"count": np.zeros((grid_size, grid_size), dtype=np.int),
"next": np.zeros(n, dtype=int)
}
num_tries, max_tries, total_tries = 0, 0, 0
for j in range(n):
done = False
while not done:
xt, yt = np.random.rand(2) * 2*r_max - r_max
rt = (xt**2 + yt**2) ** 0.5
if rt + (min_sep/2.0) > r_max:
num_tries += 1
elif r_min and rt - (min_sep/2.0) < r_min:
num_tries += 1
else:
jx = int(round(xt + r_max) * scale)
jy = int(round(yt + r_max) * scale)
x0 = max(0, jx-2)
x1 = min(grid_size, jx+3)
y0 = max(0, jy-2)
y1 = min(grid_size, jy+3)
# Find the minimum spacing between the trial point
# and other points
d_min = r_max * 2.0
for ky in range(y0, y1):
for kx in range(x0, x1):
if grid["count"][ky, kx] > 0:
i_other = grid["start"][ky, kx]
for kh in range(grid["count"][ky, kx]):
dx = xt - x[i_other]
dy = yt - y[i_other]
d_other = (dx**2 + dy**2) ** 0.5
d_min = min(d_min, d_other)
i_other = grid["next"][i_other]
if d_min >= min_sep:
x[j], y[j] = xt, yt
if grid["count"][jy, jx] == 0:
grid["start"][jy, jx] = j
else:
grid["next"][grid["end"][jy, jx]] = j
grid["end"][jy, jx] = j
grid["count"][jy, jx] += 1
max_tries = max(max_tries, num_tries)
total_tries += num_tries
num_tries = 0
done = True
else:
num_tries += 1
info = {"max_tries": max_tries, "total_tries": total_tries}
return (x, y, info)
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