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| author | Eric S. Raymond <esr@thyrsus.com> | 2013-11-02 08:46:48 -0400 |
|---|---|---|
| committer | Eric S. Raymond <esr@thyrsus.com> | 2013-11-02 08:49:04 -0400 |
| commit | ffae809ddecd0fb885f6b15407895d5b3072b1c1 (patch) | |
| tree | 3abc1dc9fba685235017ca7553d836c2a54a5cbe /gpsprof.xml | |
| parent | e29a27065d7e016376f2bc4ad9e73ab962730950 (diff) | |
| download | gpsd-ffae809ddecd0fb885f6b15407895d5b3072b1c1.tar.gz | |
gpsprof can now make plots of time deta from PPS.
I think it is revealing problems in the PPS instrumentation...
Diffstat (limited to 'gpsprof.xml')
| -rw-r--r-- | gpsprof.xml | 28 |
1 files changed, 19 insertions, 9 deletions
diff --git a/gpsprof.xml b/gpsprof.xml index 60016416..4beb6c00 100644 --- a/gpsprof.xml +++ b/gpsprof.xml @@ -38,12 +38,14 @@ BSD terms apply: see the file COPYING in the distribution root for details. <refsect1 id='description'><title>DESCRIPTION</title> -<para><application>gpsprof</application> performs accuracy and latency -profiling on a GPS. It emits to standard output a GNUPLOT program -that draws an illustrative graph. It can also be told to emit the raw -profile data. The information it provides can be useful for -establishing an upper bound on latency, and thus on position accuracy -of a GPS in motion.</para> +<para><application>gpsprof</application> performs accuracy, latency, +and time drift profiling on a GPS. It emits to standard output a +GNUPLOT program that draws one of several illustrative graphs. It can +also be told to emit the raw profile data.</para> + +<para>Information from the default spatial plot it provides can be +useful for establishing an upper bound on latency, and thus on +position accuracy of a GPS in motion.</para> <para><application>gpsprof</application> uses instrumentation built into <application>gpsd</application>.</para> @@ -68,9 +70,10 @@ gpsprof -T png | gnuplot >image.png </refsect1> <refsect1 id='options'><title>OPTIONS</title> -<para>The -f option sets the plot type. The X axis is samples -(sentences with timestamps). The Y axis is normally latency in seconds. -Currently the following plot types are defined:</para> +<para>The -f option sets the plot type. The X axis is samples (either +sentences with timestamps or PPS time drift messages). The Y axis is +normally latency in seconds, except for the spatial plot. Currently the +following plot types are defined:</para> <variablelist> <varlistentry> @@ -83,6 +86,13 @@ This is the default.</para> </listitem> </varlistentry> <varlistentry> +<term>time</term> +<listitem> +<para>Plot delta of system clock (NTP corrected time) against GPS time +as reported in PPS messages.</para> +</listitem> +</varlistentry> +<varlistentry> <term>uninstrumented</term> <listitem> <para>Plot total latency without instrumentation. Useful mainly as a |