Code Samples

Python Script to grab GPSD data and log to file.

#! /usr/bin/python

# Written by Dan Mandle http://dan.mandle.me September 2012

# License: GPL 2.0

import os

from gps import *

from time import *

import time

import threading

gpsd = None #seting the global variable

os.system('clear') #clear the terminal (optional)

class GpsPoller(threading.Thread):

    def __init__(self):

        threading.Thread.__init__(self)

        global gpsd #bring it in scope

        gpsd = gps(mode=WATCH_ENABLE) #starting the stream of info

        self.current_value = None

        self.running = True #setting the thread running to true

    def run(self):

        global gpsd

        while self.running:

            gpsd.next() #this will continue to loop and grab EACH set of gpsd info to clear the buffer

if __name__ == '__main__':

    gpsp = GpsPoller() # create the thread

    try:

        gpsp.start() # start it up

        gps_file = open('gps_data.csv','w') # Open a file to write the data to

        while True:

            if str(gpsd.fix.mode) == str(3): # If we have Mode 3, good lock, then write the data out

                gps_data = str(gpsd.fix.latitude) + ',' + str(gpsd.fix.longitude) + '\n' # just print lat and lon data

                print gps_data

                gps_file.write (gps_data)

            time.sleep(1) #set to whatever

    except (KeyboardInterrupt, SystemExit): #when you press ctrl+c

        print "\nKilling Thread..."

        gpsp.running = False

        gpsp.join() # wait for the thread to finish what it's doing

        gps_file.close()

    print "Done.\nExiting."

Python Script to plot the GPS Data on the screen

#! /usr/bin/python

# Plotting test using pygame

import pygame, sys, os, csv   # Import the pygame, sys and os libraries

from pygame.locals import * # Get pygame constants

pygame.init() # Initialise pygame

screenx = 640 # Size of window

screeny = 480

offsetx = screenx/2 # middle of window

offsety = screeny/2

firstrow = True

scale = 40000

surface=pygame.display.set_mode((screenx,screeny)) # Create a surface to draw on

pygame.display.set_caption('pygame drawng test')# Set the window caption

screen = pygame.display.get_surface()

#pygame.draw.line(surface, (0,0,255),(0,0),(200,100)) # Draw a line

#pygame.display.flip() # Display what we have drawn

gps_file = open('gps_test_data.csv','rt') # Open a file to read data from

try: # Read all the lines in

    reader = csv.DictReader(gps_file)

    for row in reader:

        #print row

        #print row['lat']

        #print row['lon']

        while firstrow: # if this is the firstrow us coords for center

 

            firstx = int(float(row['lat'])*scale) 

            firsty = int(float(row['lon'])*scale) 

            firstrow = False

            lastx=offsetx

            lasty=offsety

            #print firstx, firsty

       

        else:

            x = int(float(row['lat']) * scale)-firstx + offsetx     # make this point middle of the screen

            y = int(float(row['lon']) * scale)-firsty + offsety

            

            #print firstx,firsty, lastx,lasty,x,y

            pygame.draw.line(surface, (0,0,255),(lastx,lasty),(x,y)) # Draw a line

            pygame.display.flip()

            lastx = x

            lasty = y

finally:

    gps_file.close()

def input(events): # Function to process pygame events

    for event in events:

        if event.type == QUIT: # If we click ALT+F4 programme will quit

            sys.exit(0)

        

while True: # Keep looping getting events

    input(pygame.event.get())