Script for generating KML with track timestamps from Pixhawk logs

_pixhawkkml.md

A Python script for generating KML with timestamps from Pixhawk logs.

See the script for a few comments.

iris-flights.png

pixhawkkml.py

#!/usr/bin/env python

# Generate KML from a Pixhawk log.  Includes timestamps so that a
# Google Earth time slider is available.  Also include any data you
# want.  Using the Elevation Profile, you can plot this data over
# time within Google Earth.

# Reads 'iris.log' and writes 'iris.kml'.

import csv
from datetime import datetime

gps_epoch_ms = 315964800

def unix_time(week,ms):
    return gps_epoch_ms + ms/1000.0 + (week * 7 * 24 * 60 * 60)

def ms_iso(ms):
    return datetime.fromtimestamp(ms).isoformat()


inFilename = "iris.log"

out = open('iris.kml', 'w')

out.write("<?xml version='1.0' encoding='UTF-8'?>\n")
out.write("<kml xmlns=\"http://www.opengis.net/kml/2.2\" xmlns:gx=\"http://www.google.com/kml/ext/2.2\">\n")
out.write("<Document>\n")
out.write("  <Schema id=\"schema\">\n")
out.write("    <gx:SimpleArrayField name=\"gps_alt\" type=\"float\">\n")
out.write("      <displayName>GPS Alt</displayName>\n")
out.write("    </gx:SimpleArrayField>\n")
out.write("    <gx:SimpleArrayField name=\"ahr_alt\" type=\"float\">\n")
out.write("      <displayName>AHR Alt</displayName>\n")
out.write("    </gx:SimpleArrayField>\n")
out.write("  </Schema>\n")

out.write("  <Folder>\n")
out.write("    <name>" + inFilename + "</name>\n")
out.write("    <Placemark>\n")
out.write("      <gx:Track>\n")
out.write("       <altitudeMode>absolute</altitudeMode>\n")
# out.write("       <altitudeMode>relativeToGround</altitudeMode>\n")

# gx:Track wants its time stamps before is coordinates.  Really
# strange.  Rather than keeping lots of data in memory, we make
# multiple passes over the file.  We won't run out of memory.  Due to
# page caching, shouldn't be that slow, either.

# Emit timestamps and find min baro.
min_baro = -1
with open(inFilename) as input:
    data = csv.reader(input, delimiter = ',')
    for row in data:
        if len(row) == 0:
            continue
        if row[0] == 'BARO':
            baro = float(row[3])
            if min_baro < 0 or baro < min_baro:
                min_baro = baro
            continue
        if row[0] == 'GPS':
            ms = int(row[2])
            week = int(row[3])
            iso = ms_iso(unix_time(week,ms))
            out.write("       <when>" + iso + "</when>\n")

# Emit GPS coordinates along with latest baro
with open(inFilename) as input:
    data = csv.reader(input, delimiter = ',')
    rel_baro = 0
    for row in data:
        if len(row) == 0:
            continue
        if row[0] == 'BARO':
            rel_baro = (float(row[3]) - min_baro)/10.0
            continue
        if row[0] == 'GPS':
            # Which altitude do we want to report here?
            # Originally I was debugging a mini-fly-away.
            baro_alt = rel_baro
            gps_alt = row[9]
            # If using gps_alt, use altitudeMode: absolute instead of
            # relativeToGround.
            out.write("       <gx:coord>" + str(row[7]) + "," + str(row[6]) + "," + str(gps_alt) + "</gx:coord>\n")


# Emit data associated with each point.

out.write("       <ExtendedData>\n")

with open(inFilename) as input:
    data = csv.reader(input, delimiter = ',')

    out.write("         <SchemaData schemaUrl=\"#gps_alt\">\n")
    out.write("           <gx:SimpleArrayData name=\"GPS Alt\">\n")
    for row in data:
        if len(row) == 0:
            continue
        if row[0] == 'GPS':
            gps_alt = row[9]
            out.write("             <gx:value>" + str(gps_alt) + "</gx:value>\n")

out.write("           </gx:SimpleArrayData>\n")
out.write("         </SchemaData>\n")

with open(inFilename) as input:
    data = csv.reader(input, delimiter = ',')

    out.write("         <SchemaData schemaUrl=\"#ahr_alt\">\n")
    out.write("           <gx:SimpleArrayData name=\"AHR Alt\">\n")
    ahr_alt = 0
    for row in data:
        if len(row) == 0:
            continue
        if row[0] == 'AHR2':
            ahr_alt = row[5]
        if row[0] == 'GPS':
            out.write("             <gx:value>" + str(ahr_alt) + "</gx:value>\n")

out.write("           </gx:SimpleArrayData>\n")
out.write("         </SchemaData>\n")

out.write("       </ExtendedData>\n")

out.write("      </gx:Track>\n")
out.write("    </Placemark>\n")
out.write("  </Folder>\n")
out.write("</Document>\n")
out.write("</kml>\n")
out.close()