Processing a GPX file with xsl (probably a namespace issue) - xslt

Question

This question looks like a duplicate of XPath query for GPX files with namespaces?, but I must be missing something because I can't seem to get a fairly simple style sheet to work. I have this input:
<?xml version="1.0" encoding="utf-8"?>
<gpx xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.0" creator="Groundspeak Pocket Query" xsi:schemaLocation="http://www.topografix.com/GPX/1/0 http://www.topografix.com/GPX/1/0/gpx.xsd http://www.groundspeak.com/cache/1/0 http://www.groundspeak.com/cache/1/0/cache.xsd" xmlns="http://www.topografix.com/GPX/1/0">
<name>Ottawa Pocket Query</name>
<wpt lat="45.348517" lon="-75.825933">
<name>GC3HXAZ</name>
<desc>Craft maker box by FishDetective, Traditional Cache (2/2.5)</desc>
<url>http://www.geocaching.com/seek/cache_details.aspx?guid=e86ce3f5-9e75-48a6-b47e-9415101fc658</url>
<groundspeak:cache id="2893138" available="True" archived="False" xmlns:groundspeak="http://www.groundspeak.com/cache/1/0">
<groundspeak:name>Craft maker box</groundspeak:name>
<groundspeak:difficulty>2</groundspeak:difficulty>
<groundspeak:terrain>2.5</groundspeak:terrain>
</groundspeak:cache>
</wpt>
</gpx>
And a stylesheet that looks like this:
<?xml version="1.0"?>
<!-- -->
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:groundspeak="http://www.groundspeak.com/cache/1/0"
>
<xsl:output method="html"/>
<xsl:template match="/">
Cache names:
<xsl:apply-templates select="//wpt">
</xsl:apply-templates>
</xsl:template>
<xsl:template match="wpt">
<li><xsl:value-of select="groundspeak:cache/groundspeak:name"/></li>
</xsl:template>
</xsl:stylesheet>
And what I would expect is a list with one element on it, "Craft Maker Box", but what I get is an empty list.
What am I missing?

Answer 1

The default namespace is http://www.topografix.com/GPX/1/0. You should add that and use a prefix to match wpt.
Something like this: (untested)
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:groundspeak="http://www.groundspeak.com/cache/1/0"
xmlns:gpx="http://www.topografix.com/GPX/1/0"
>
<xsl:output method="html"/>
<xsl:template match="/">
Cache names:
<xsl:apply-templates select="//gpx:wpt">
</xsl:apply-templates>
</xsl:template>
<xsl:template match="gpx:wpt">
<li><xsl:value-of select="groundspeak:cache/groundspeak:name"/></li>
</xsl:template>
</xsl:stylesheet>

Answer 2

It is indeed a namespace issue. You have
xmlns="http://www.topografix.com/GPX/1/0"
in the XML so unprefixed element names are in this namespace. You need to bind the same uri to a prefix in your stylesheet, e.g.
xmlns:g="http://www.topografix.com/GPX/1/0"
and then use g:wpt in the match and select expressions.