Reading data from GPS devices
Invisible Pacemaker
Once I have the YAML data, I can easily write applications in Perl and other languages that interpret the stored GPS data. One feature I really miss with my Garmin 10 (and that my previously used Garmin Forerunner 101 had) is the so-called Virtual Partner.
With this feature, runners can program in the speed of a virtual pacesetter, who runs at constant speed and crosses the finish line at precisely the expected time by definition. During the run, the GPS device indicates how far the virtual runner's legs have taken them. If the pacemaker is 100 yards ahead, I need to speed up, if it drops back, I can slow down, and if we are jogging together, I am sure to finish on time.
Listing 3 implements a function to compare two runs in a similar way for my new GPS device. It uses two FIT files converted into YAML format, reads the distance
and timestamp
entries, and draws a graph with the distances covered by the two runners at specific times. The x-axis shows the elapsed running time in seconds, and the y-axis visualizes the distance covered by the runners in meters.
Listing 3
vrunner
Both FIT files were created during real runs. After my sporting excursion (Figure 2), I completed another training run on the same route. I wanted to find out whether a slightly slower pace in the first few miles would leave me feeling stronger for the final sprint and leave enough breathing room to manage a few hills in between (elevation difference about 300 feet).
The CPAN Imager::Plot module plots the data passed in as an array on the coordinate system and labels the axes nicely. The data_extract()
function in line 59 expects a YAML file with the FIT data and returns an array. It contains x/y value pairs of stored combinations of timestamps and distances traveled.
Line 74 removes the unit, m
for "meters," from the value for distance
, leaving only the numeric value. The variable $base
is set to the timestamp of the first entry, so that vrunner
can later only add timestamps relative to this base point and append them to the resulting array.
Clockwork Horse
The green graph in Figure 6 shows the first, fast run; the red graph was created after the second, slower run. The comparison shows that I was unable to translate the power reserves gained by the slower starting pace into a faster second half. Once I'm in motion, I seem to run like clockwork – without anyone dangling a carrot in front of my nose, I seem to run no faster than necessary.
![](/var/linux_magazin/storage/images/linux-magazine.com/issues/2013/145/perl-reading-gps-data/figure-6/584237-1-eng-US/Figure-6_large.png)
Infos
- Forerunner 10: http://sites.garmin.com/forerunner10/
- Garmin: http://connect.garmin.com
- FIT SDK: http://www.thisisant.com/resources/fit/
- The Garmin::FIT Perl module by Kiyokazu Suto: http://pub.ks-and-ks.ne.jp/cycling/GarminFIT.shtml
- Listings for this article: ftp://ftp.linux-magazin.com/pub/listings/magazine/153
« Previous 1 2
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
![Learn More](https://www.linux-magazine.com/var/linux_magazin/storage/images/media/linux-magazine-eng-us/images/misc/learn-more/834592-1-eng-US/Learn-More_medium.png)
News
-
NVIDIA Released Driver for Upcoming NVIDIA 560 GPU for Linux
Not only has NVIDIA released the driver for its upcoming CPU series, it's the first release that defaults to using open-source GPU kernel modules.
-
OpenMandriva Lx 24.07 Released
If you’re into rolling release Linux distributions, OpenMandriva ROME has a new snapshot with a new kernel.
-
Kernel 6.10 Available for General Usage
Linus Torvalds has released the 6.10 kernel and it includes significant performance increases for Intel Core hybrid systems and more.
-
TUXEDO Computers Releases InfinityBook Pro 14 Gen9 Laptop
Sporting either AMD or Intel CPUs, the TUXEDO InfinityBook Pro 14 is an extremely compact, lightweight, sturdy powerhouse.
-
Google Extends Support for Linux Kernels Used for Android
Because the LTS Linux kernel releases are so important to Android, Google has decided to extend the support period beyond that offered by the kernel development team.
-
Linux Mint 22 Stable Delayed
If you're anxious about getting your hands on the stable release of Linux Mint 22, it looks as if you're going to have to wait a bit longer.
-
Nitrux 3.5.1 Available for Install
The latest version of the immutable, systemd-free distribution includes an updated kernel and NVIDIA driver.
-
Debian 12.6 Released with Plenty of Bug Fixes and Updates
The sixth update to Debian "Bookworm" is all about security mitigations and making adjustments for some "serious problems."
-
Canonical Offers 12-Year LTS for Open Source Docker Images
Canonical is expanding its LTS offering to reach beyond the DEB packages with a new distro-less Docker image.
-
Plasma Desktop 6.1 Released with Several Enhancements
If you're a fan of Plasma Desktop, you should be excited about this new point release.