Compute distance and interpolate speed along path of coordinates and timestamps

path_distance.py

from sys import argv
import csv
import dateutil.parser
from geopy.distance import vincenty
'''
Input file is downloaded movements from Savi Tracking
column 1 (a.k.a. row[0]) = lat
column 2 (a.k.a. row[1]) = lng
column 3 (a.k.a. row[2]) = utc time
'''
# Pass the filename as an arg, use it to open the CSV reader
source = open(argv[1]) 
reader = csv.reader(source)

# Set default agg values
row_num = 0
max_speed = 0
total_t = 0
total_s = 0

# Loop through the file and increment
for row in reader:
    # Skip the header
    if row_num == 0:
        pass
    
    # Use the first data row as the starting point
    elif row_num == 1:
        last_loc = (float(row[0]), float(row[1]))
        last_ts = dateutil.parser.parse(str(row[2]))
    
    # Calculated deltas from last point and aggregate 
    else:   
        this_loc = (float(row[0]), float(row[1]))
        this_ts = dateutil.parser.parse(str(row[2]))
        
        delta_s = vincenty(last_loc, this_loc).km
        delta_t = (this_ts - last_ts).total_seconds()

        total_s += delta_s
        total_t += delta_t
        try:
            speed = delta_s / delta_t * 3600
            if speed > max_speed: max_speed = speed
            if speed > 80: msg = ' * GPS Drift *'
            else: msg = ''
        except ZeroDivisionError:
            speed = 0
        
        # Make these values the last values
        last_loc = this_loc
        last_ts = this_ts

        # Print so far
        print "Clock: %-26s\tDelta S: %-4.3f km\tDelta T: %-4.2f sec\tSpeed: %-5.2f kph%s" % \
         (this_ts, delta_s, delta_t, speed, msg)

    row_num += 1 

# Wrap it up
try:
    avg_speed = total_s / total_t * 3600
except ZeroDivisionError:
    avg_speed = 0

print "Traversed %.3f km in %.2f minutes." % (total_s, total_t / 60)
print "Max Speed = %.2f kph.\tAvg speed = %.2f kph" % (max_speed, avg_speed)

source.closed