Bureau of Meteorology Single-Site JSON to APRS Uploader

bom_obs_to_aprs.py

#
#  BOM JSON Observation to APRS Uploader
#
#  Mark Jessop <[email protected]>
#  2018-01-06
#
#	This is intended to be run as a regular (5-10 minute) cron job.
#	Update the JSON feed, APRS_CALL, APRS_PASSCODE, and WX_CALL Fields below before using.
#
#	A link to the single-station observation JSON feed can be found at the bottom of an observation page,
#	I.e. http://www.bom.gov.au/products/IDS60801/IDS60801.94648.shtml
#

import requests
import json
import sys
import traceback
import logging
from socket import *


# SETTINGS

# URL to the JSON feed.
BOM_JSON_URL = "http://www.bom.gov.au/fwo/IDS60801/IDS60801.94648.json" # Adelaide (West Terrace)

# Login details for APRS-IS
APRS_CALL = 'N0CALL'
APRS_PASSCODE = 00000

# The object name of the weather station on APRS.
WX_CALL = 'IDS60801'

# Write data to a temporary file for checking.
# This file will be writen if it does not exist.
TEMP_FILE = './bom_obs.json'

def upload_to_aprs(aprsUser, aprsPass, wx_call, data, serverHost = 'rotate.aprs2.net', serverPort = 14580):
	''' Upload an APRS packet to APRS-IS '''
	sSock = socket(AF_INET, SOCK_STREAM)
	sSock.connect((serverHost, serverPort))
	# logon
	sSock.send('user %s pass %s vers VK5QI-Python 0.1\n' % (aprsUser, aprsPass) )
	# send packet
	sSock.send('%s>APRS:%s\n' % (wx_call, data) )
	
	# close socket
	sSock.shutdown(0)
	sSock.close()



def str_or_dots(number, length):
    """
    If parameter is None, fill space with dots. Else, zero-pad.
    """
    if number is None:
        return '.'*length
    else:
        format_type = {
            'int': 'd',
            'float': '.0f',
        }[type(number).__name__]
        return ''.join(('%0',str(length),format_type)) % number


def make_aprs_wx(lat_str, lon_str, comment="BOMWX", wind_dir=None, wind_speed=None, wind_gust=None, temperature=None, rain_since_midnight=None, humidity=None, pressure=None):
    """
    Assembles the payload of the APRS weather packet.
    """

    return '!%s/%s_%s/%sg%st%sP%sh%sb%s%s' % (
    	lat_str,
    	lon_str,
        str_or_dots(wind_dir, 3),
        str_or_dots(wind_speed, 3),
        str_or_dots(wind_gust, 3),
        str_or_dots(temperature, 3),
        str_or_dots(rain_since_midnight, 3),
        str_or_dots(humidity, 2),
        str_or_dots(pressure, 5),
        comment
    )

# Lookup table to convert cardinal directions to degrees.
cardinal_lookup = {
	'N': 0,
	'NNE': 22,
	'NE': 45,
	'ENE': 67,
	'E': 90,
	'ESE': 112,
	'SE': 135,
	'SSE': 157,
	'S': 180,
	'SSW': 202,
	'SW': 225,
	'WSW': 247,
	'W': 270,
	'WNW': 292,
	'NW': 315,
	'NNW': 337,
	'CALM': 0
}

# Example BOM JSON blob
#{u'swell_period': None, u'wind_dir': u'SSW', u'lat': -34.4, u'cloud_oktas': None, u'gust_kt': 24, u'history_product': u'IDS60801', u'local_date_time_full': u'20180106200000', u'cloud': u'-', u'press_msl': 1008.0, u'cloud_type': u'-', u'wind_spd_kmh': 28, u'lon': 140.6, u'swell_height': None, u'wmo': 94682, u'press_qnh': 1008.1, u'weather': u'-', u'wind_spd_kt': 15, u'rain_trace': u'0.0', u'aifstime_utc': u'20180106093000', u'delta_t': 15.0, u'press_tend': u'-', u'rel_hum': 17, u'local_date_time': u'06/08:00pm', u'press': 1008.0, u'vis_km': u'-', u'sea_state': u'-', u'air_temp': 33.5, u'name': u'Loxton', u'cloud_base_m': None, u'cloud_type_id': None, u'gust_kmh': 44, u'dewpt': 5.6, u'swell_dir_worded': u'-', u'sort_order': 0, u'apparent_t': 27.2}

def bom_json_to_aprs(obs):
	''' Convert a BOM JSON observation into an APRS weather report packet '''

	# Convert float latitude to APRS format (DDMM.MM)
	lat = float(obs["lat"])
	lat_degree = abs(int(lat))
	lat_minute = abs(lat - int(lat)) * 60.0
	lat_min_str = ("%02.2f" % lat_minute).zfill(5)
	lat_dir = "S"
	if lat>0.0:
		lat_dir = "N"
	lat_str = "%02d%s" % (lat_degree,lat_min_str) + lat_dir
	
	# Convert float longitude to APRS format (DDDMM.MM)
	lon = float(obs["lon"])
	lon_degree = abs(int(lon))
	lon_minute = abs(lon - int(lon)) * 60.0
	lon_min_str = ("%02.2f" % lon_minute).zfill(5)
	lon_dir = "E"
	if lon<0.0:
		lon_dir = "W"
	lon_str = "%03d%s" % (lon_degree,lon_min_str) + lon_dir

	# Convert temperature to Farenheit (ugh)
	temp_f = float(obs['air_temp']) * (9.0/5.0) + 32

	# Convert pressure to hPa*10
	press_hpa = int(obs['press']*10)

	# Convert rain in mm to hundredths of an inch
	rain_in = float(obs['rain_trace']) * 3.93700787

	# Convert wind speeds to miles per hour
	wind_speed = obs['wind_spd_kt'] * 1.15077945
	wind_gust = obs['gust_kt'] * 1.15077945

	# Convert cardinal direction to degrees using lookup table
	if obs['wind_dir'] in cardinal_lookup:
		wind_dir = cardinal_lookup[obs['wind_dir']]
	else:
		wind_dir = None


	# Produce the APRS weather report string, using the above function.
	aprs_str = make_aprs_wx(lat_str, 
							lon_str, 
							temperature = temp_f,
							pressure = press_hpa,
							rain_since_midnight = rain_in,
							humidity = float(obs['rel_hum']),
							wind_speed = wind_speed,
							wind_gust = wind_gust,
							wind_dir = wind_dir)

	return aprs_str
	

def get_bom_json(url):
	''' Grab JSON data from the BOM website, and return the latest observation '''
	try:
		# Wrap all this in a try/catch to avoid errors.
		# Grab the data from the BOM website.
		bom_request = requests.get(url)
		json_data = bom_request.text

		# Parse the JSON data into a Python Dictionary
		parsed_data = json.loads(json_data)

		# Extract the most recent observation
		latest_obs = parsed_data['observations']['data'][0]

		return latest_obs
	except Exception as e:
		print("ERROR: Grabbing data from BOM Failed: " + traceback.format_exc())
		return None


if __name__ == '__main__':

	# Grab latest observation.
	_obs = get_bom_json(BOM_JSON_URL)

	# Attempt to read the temp observation file.
	try:
		_temp_file = open(TEMP_FILE, 'r')
		_temp_data = _temp_file.read()
		data = json.loads(_temp_data)
		_temp_file.close()

		# Is the timestamp in the observation different? 
		if data['aifstime_utc'] == _obs['aifstime_utc']:
			new_obs = False
		else:
			new_obs = True

	except Exception as e:
		print("Error reading stored observation, assuming observation is new: %s" % str(e))
		new_obs = True

	if new_obs:
		# Write current observation to disk.
		_temp_file = open(TEMP_FILE, 'w')
		_temp_file.write(json.dumps(_obs))
		_temp_file.close()

		# Produce APRS string.
		aprs_str = bom_json_to_aprs(_obs)
		print("APRS String: %s" % aprs_str)
		print("Uploading to APRS...")
		upload_to_aprs(APRS_CALL, APRS_PASSCODE, WX_CALL, aprs_str)

	else:
		print("Not a new observation, Exiting.")
		sys.exit(0)