Using the Command Line Utilities
In addition to the GUI, Golden Cheetah comes with
several command line utilities:
ptdl , which downloads ride data from a PowerTap Pro version 2.21
cycling computer, ptunpk , which unpacks the raw bytes downloaded
by ptdl and outputs more human-friendly ride information, and
cpint , which computes your critical power (see below). We've
also written several Perl scripts to help you graph and summarize the data.
NOTE: We no longer support the use of the command-line tools. Please use the
graphical version of GoldenCheetah instead. This documentation is here for
the benefit of the brave alone.
Extracting the Data
First, make sure you have the FTDI drivers installed, as described in the User's Guide. You can then run ptdl
without arguments:
$ ./ptdl
Reading from /dev/tty.usbserial-3B1.
Reading version information...done.
Reading ride time...done.
Writing to 2006_05_15_11_34_03.raw.
Reading ride data..............done.
$ head -5 2006_05_15_11_34_03.raw
57 56 55 64 02 15
60 06 05 0f 6b 22
40 08 30 00 00 00
86 0e 74 99 00 55
81 06 77 a8 40 55
If everything goes well, ptdl will automatically detect the
device (/dev/tty.usbserial-3B1 in the example above), read the
ride data from it, and write to a file named by the date and time at which the
ride started (2006_05_15_11_34_03.raw in the example; the format
is YYYY_MM_DD_hh_mm_ss.raw).
Unpacking the Data
As shown by the head command above, the data in this
.raw file is just the raw bytes that represent your ride. To
unpack those bytes and display them in a more human-friendly format, use
ptunpk :
$ ./ptunpk 2006_05_15_11_34_03.raw
$ head -5 2006_05_15_11_34_03.dat
# Time Torq MPH Watts Miles Cad HR Int
# 2006/5/15 11:34:03 1147707243
# wheel size=2096 mm, interval=0, rec int=1
0.021 13.1 2.450 43 0.00781 0 85 0
0.042 13.4 5.374 97 0.00912 64 85 0
ptunpk takes a .raw file for input and writes a
.dat file as output. Lines that start with an ampersand ("#") in
this file are comments; the other lines represent measured samples. As shown
by the first comment in the file, the columns are: time in minutes, torque in
Newton-meters, speed in miles per hour, power in watts, distance in miles,
cadence, heart rate, and interval number.
Summarizing the Data
We hope to have a graphical interface to these programs soon, but until then,
the only summarization tools we have are command-line programs. The script
intervals.pl summarizes the intervals performed in a workout:
$ ./intervals.pl 2006_05_03_16_24_04.dat
Power Heart Rate Cadence Speed
Int Dur Dist Avg Max Avg Max Avg Max Avg Max
0 77:10 19.3 213 693 134 167 82 141 16.0 27.8
1 4:03 0.9 433 728 175 203 84 122 13.0 18.8
2 7:23 1.0 86 502 135 179 71 141 16.0 28.2
3 4:27 0.9 390 628 170 181 70 100 12.0 17.6
4 8:04 0.9 60 203 130 178 50 120 18.0 30.1
5 4:30 0.9 384 682 170 179 79 113 11.0 18.6
6 8:51 1.1 53 245 125 176 70 141 8.0 26.6
7 2:48 0.4 400 614 164 178 62 91 8.0 13.6
8 7:01 1.1 46 268 128 170 71 141 12.0 28.8
9 4:30 0.9 379 560 168 180 81 170 11.0 18.3
10 28:46 6.5 120 409 128 179 79 141 15.0 31.0
In the example above, a rider performed five hill intervals, four of which
climbed a medium size hill that took about 4-5 minutes to climb (intervals
1, 3, 5, and 9), and one on a shorter hill that took just under 3 minutes to
climb (interval 7).
Graphing the Data
For graphing the data in the ride, we use smooth.pl and the
gnuplot program. You can use sample.gp
to graph the power, heart rate, cadence, and speed for the hill workout above:
$ gnuplot sample.gp
Finding Your "Critical Power"
Joe Friel calls the maximum average power a rider can sustain over an interval
the rider's "critical power" for that duration. The cpint
program automatically computes your critical power over all interval lengths
using the data from all your past rides. This program looks at all the
.raw files in a directory, calculating your maximum power over
every subinterval length and storing them in a corresponding .cpi
file. It then combines the data in all of the .cpi files to find
your critical power over all subintervals of all your rides.
$ ls *.raw
2006_04_28_10_48_33.raw 2006_05_10_17_08_30.raw 2006_05_18_16_32_53.raw
2006_05_03_16_24_04.raw 2006_05_13_10_29_12.raw 2006_05_21_12_25_07.raw
2006_05_05_10_52_05.raw 2006_05_15_11_34_03.raw 2006_05_22_18_28_47.raw
...
2006_05_09_09_54_29.raw 2006_05_17_16_44_35.raw
$ ./cpint
Compiling data for ride on Fri Apr 28 10:48:33 2006...done.
Compiling data for ride on Sat Apr 29 10:07:48 2006...done.
Compiling data for ride on Sun Apr 30 14:00:17 2006...done.
...
Compiling data for ride on Mon May 22 18:28:47 2006...done.
0.021 1264
0.042 1221
0.063 1216
...
5.019 391
...
171.885 163
Over this set of rides, the rider's maximum power is 1264 watts, achieved over
an interval of 0.021 minutes (1.26 seconds). Over all five-minute
subintervals, he has achieved a maximum average power of 391 watts. The
longest ride in this set was 171.885 minutes long, and he averaged 163 watts
over it.
We can graph the output of cpint using gnuplot with
cpint.gp:
$ ./cpint > cpint.out
$ gnuplot cpint.gp
The first time you run cpint it will take a while, as it has to
analyze all your past rides. On subsequent runs, however, it will only
analyze new files.
Training and Racing with a Power Meter (see the FAQ) contains a table of critical powers of Cat 5 cyclists
up through international pros at interval lengths of 5 seconds, 1 minute, 5
minutes, and 60 minutes. Using this table and the cpint program,
you can determine whether you're stronger than others in your racing category
at each interval length and adapt your training program accordingly.
Converting Old Data
If you've used the PowerTuned software that comes with the PowerTap you may
have lots of old ride data in that program that you'd like to include in your
critical power graph. You can convert the .xml files that
PowerTuned produces to .raw files using the ptpk
program:
$ ./ptpk 2006_04_27_00_23_28.xml
$ head -5 2006_04_27_00_23_28.raw
57 56 55 64 02 15
60 06 04 7b 80 17
40 08 30 00 00 00
84 04 00 24 00 ff
83 03 00 d7 00 ff
ptpk assumes the input .xml file was generated with
a wheel size of 2,096 mm and a recording interval of 1. If this is not the
case, you should specify the correct values with the -w and
-r options.
Note that the PowerTuned software computes the output speed in miles per hour
by multiplying the measured speed in kilometers per hour by 0.62, and the
miles per hour values in a .xml file are thus only accurate to
two significant figures, even though they're printed out to three decimal
places. Because of this limitation, the sequence ptpk ,
ptunpk is not quite the identity function; in particular, the
wattage values from ptpk may only be accurate to two significant
digits.
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