From 6e2bde98964b4d1fb87da24049388e9bf87f7222 Mon Sep 17 00:00:00 2001
From: robertl <robertl@f51c46e8-681c-474f-0cfe-069cfd0219fb>
Date: Wed, 6 Feb 2008 02:29:22 +0000
Subject: [PATCH] Add option to 'discard' filter to require minimum number of
 satellites.

git-svn-id: http://gpsbabel.googlecode.com/svn/trunk@3080 f51c46e8-681c-474f-0cfe-069cfd0219fb
---
 gpsbabel/discard.c                  | 14 ++++++++++++++
 gpsbabel/xmldoc/filters/discard.xml | 24 +++++++++++++++++++-----
 2 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/gpsbabel/discard.c b/gpsbabel/discard.c
index d8f1942c5..0a8d29e4d 100644
--- a/gpsbabel/discard.c
+++ b/gpsbabel/discard.c
@@ -26,8 +26,10 @@
 static char *hdopopt = NULL;
 static char *vdopopt = NULL;
 static char *andopt = NULL;
+static char *satopt = NULL;
 static double hdopf;
 static double vdopf;
+static int satpf;
 static gpsdata_type what;
 static route_head *head;
 
@@ -39,6 +41,8 @@ arglist_t fix_args[] = {
 		"-1.0", ARGTYPE_END_REQ | ARGTYPE_FLOAT, ARG_NOMINMAX},
 	{"hdopandvdop", &andopt, "Link hdop and vdop supression with AND",
 		NULL, ARGTYPE_BOOL, ARG_NOMINMAX},
+	{"sat", &satopt, "Minimium sats to keep waypoints",
+		"-1.0", ARGTYPE_BEGIN_REQ | ARGTYPE_INT, ARG_NOMINMAX},
 	ARG_TERMINATOR
 };
 
@@ -51,6 +55,7 @@ fix_process_wpt(const waypoint *wpt)
 	int del = 0;
 	int delh = 0;
 	int delv = 0;
+	
 	waypoint *waypointp = (waypoint *) wpt;
 
 	if ((hdopf >= 0.0) && (waypointp->hdop > hdopf))
@@ -62,6 +67,9 @@ fix_process_wpt(const waypoint *wpt)
 		del = delh && delv;
 	else
 		del = delh || delv;
+		
+        if ((satpf >= 0) && (waypointp->sat < satpf))
+		del = 1;
 
 	if (del) {
 		switch(what) {
@@ -116,6 +124,12 @@ fix_init(const char *args)
 		vdopf = atof(vdopopt);
 	else
 		vdopf = -1.0;
+	
+	if (satopt)
+		satpf = atoi(satopt);
+	else
+		satpf = -1;
+		
 }
 
 filter_vecs_t discard_vecs = {
diff --git a/gpsbabel/xmldoc/filters/discard.xml b/gpsbabel/xmldoc/filters/discard.xml
index 82bd9bf90..9b2a2ad26 100644
--- a/gpsbabel/xmldoc/filters/discard.xml
+++ b/gpsbabel/xmldoc/filters/discard.xml
@@ -1,12 +1,26 @@
 <para>
 This filter is used to "fix" unreliable GPS data by discarding points
-with HDOP and/or VDOP above a specified limit.  HDOP and VDOP are 
-measures of the best possible horizontal or vertical precision 
-for a given configuration of GPS satellites.
+that are believed to be unreliable.  You may specify an 
+HDOP and/or VDOP above a specified limit, a minimum number of satellits
+that must have been in view for a fix to be considered, or both.
 </para>
+<para>
+HDOP and VDOP are measures of the best possible horizontal or vertical precision for a given configuration of GPS satellites.   Higher numbers indicate a higher dilution of precision and therefore mathematically less useful.
+</para>
+<para>
 <example id="example_discard_filter">
-<title>Using the discard filter</title>
+<title>Using the discard filter for HDOP and VDOP. </title>
 <para><userinput> gpsbabel -i gpx -f in.gpx -x discard,hdop=10,vdop=20,hdopandvdop -o gpx -F out.gpx</userinput></para>
 </example>
-<para> Contributed by Tobias Minich.</para>
+</para>
+<para>
+You may specify a minimmum number of  satellites.  
+</para>
+<para>
+<example id="example_discard_filter_sats">
+<title>Using the discard filter to require at least three satellites. </title>
+<para><userinput> gpsbabel -i gpx -f in.gpx -x discard,sat=3 -o gpx -F out.gpx</userinput></para>
+</example>
+</para>
+<para> Contributed by Tobias Minich and Serge Droz. </para>
       
-- 
2.30.2