Golf Course Optimization with Raspberry Pi and Hologram Nova

import serial
import os

# Library for managing Google Sheets update and authentication
import gspread

# Version 2 libraries:
import time
import sys
import paho.mqtt.client as mqtt
import json

from oauth2client.service_account import ServiceAccountCredentials

# Hologram cloud library for cellular comminucations
from Hologram.HologramCloud import HologramCloud

hologram = HologramCloud(dict(), network='cellular')

result = hologram.network.connect()
if result == False:
    print ('Failed to connect to cell network')

# Use creds to create a client to interact with the Google Drive API
scope = ['https://spreadsheets.google.com/feeds']
creds = ServiceAccountCredentials.from_json_keyfile_name('client_secret.json', scope)
client = gspread.authorize(creds)

# Name of the Google Sheet and the specific worksheet
sheet = client.open("Golfer Tracker").worksheet("PlacemarkData")

# Version 2 - Specify Thingsboard server and access token
THINGSBOARD_HOST = 'demo.thingsboard.io'
ACCESS_TOKEN = '<your access_token>'

# Version 2 - Specify interval to reduce cellular data usage
INTERVAL=10
next_reading = time.time()

# Version 2 - Initialize mqtt
gps_data = {'latitude': 0, 'longitude': 0}
client = mqtt.Client()
client.username_pw_set(ACCESS_TOKEN)

# Version 2 - Connect to ThingsBoard using default MQTT port and 60 seconds keepalive interval
client.connect(THINGSBOARD_HOST, 1883, 60)
client.loop_start()

# GPS fix flag will go true after first fix
firstFixFlag = False
firstFixDate = ""

# Set up serial:
ser = serial.Serial(
    port='/dev/ttyUSB0',\
    baudrate=4800,\
    parity=serial.PARITY_NONE,\
    stopbits=serial.STOPBITS_ONE,\
    bytesize=serial.EIGHTBITS,\
        timeout=1)

# Helper function to take HHMM.SS, Hemisphere and make it decimal:
def degrees_to_decimal(data, hemisphere):
    try:
        decimalPointPosition = data.index('.')
        degrees = float(data[:decimalPointPosition-2])
        minutes = float(data[decimalPointPosition-2:])/60
        output = degrees + minutes
        if hemisphere is 'N' or hemisphere is 'E':
            return output
        if hemisphere is 'S' or hemisphere is 'W':
            return -output
    except:
        return ""

# Helper function to take a $GPRMC sentence, and turn it into a Python dictionary.
# This also calls degrees_to_decimal and stores the decimal values as well.
def parse_GPRMC(data):
    data = data.split(',')
    dict = {
            'fix_time': data[1],
            'validity': data[2],
            'latitude': data[3],
            'latitude_hemisphere' : data[4],
            'longitude' : data[5],
            'longitude_hemisphere' : data[6],
            'speed': data[7],
            'true_course': data[8],
            'fix_date': data[9],
            'variation': data[10],
            'variation_e_w' : data[11],
            'checksum' : data[12]
    }
    dict['decimal_latitude'] = degrees_to_decimal(dict['latitude'], dict['latitude_hemisphere'])
    dict['decimal_longitude'] = degrees_to_decimal(dict['longitude'], dict['longitude_hemisphere'])
    return dict

# Main program loop:
while True:
    line = ser.readline()
    if "$GPRMC" in line: # This will exclude other NMEA sentences the GPS unit provides
        gpsData = parse_GPRMC(line) # Turn a GPRMC sentence into a Python dictionary called gpsData
        if gpsData['validity'] == "A": # If the sentence shows that there's a fix, then we can log the line
            if firstFixFlag is False: # If we haven't found a fix before, then set the filename prefix with GPS date & time.
                firstFixDate = gpsData['fix_date'] + "-" + gpsData['fix_time']
                firstFixFlag = True
            else: # write the data to a simple log file and then to Google Sheets:
                with open("/home/pi/gps_experimentation/" + firstFixDate +"-simple-log.txt", "a") as myfile:
                    myfile.write(gpsData['fix_date'] + "," + gpsData['fix_time'] + "," + str(gpsData['decimal_latitude']) + "," + str(gpsData['decimal_longitude']) +"\n")
                print (gpsData['fix_date'] + "," + gpsData['fix_time'] + "," + str(gpsData['decimal_latitude']) + "," + str(gpsData['decimal_longitude']) +"\n")
                # Write location data to the Google Sheet
                sheet.update_cell(11, 5, str(gpsData['decimal_latitude'])) 
                sheet.update_cell(11, 6, str(gpsData['decimal_longitude']))
                # Version 2 - Write location data to Thingsboard 
                gps_data['latitude'] = str(gpsData['decimal_latitude'])
                gps_data['longitude'] = str(gpsData['decimal_longitude'])
                client.publish('v1/devices/me/telemetry', json.dumps(gps_data), 1)

                # Version 2 - Interval timing control
                next_reading += INTERVAL
                sleep_time = next_reading-time.time()
                if sleep_time > 0:
                    time.sleep(sleep_time)

client.loop_stop()
client.disconnect()

# Disconnect from the cellular network
hologram.network.disconnect()