I can't find a good Garmin forum for my question; however, this one appears to be the most relevant.
https://www8.garmin.com/support/download_details.jsp?id=927
POI Loader for Windows allows you to load custom points of interest into your unit. The input files can be downloaded from the internet or you can create your own.
I have I website (https://gpx-poi.com/) that can be used to create GPX input files. Where can I find documentation that will allow me to perform a schema validation of these files?
This is the only documentation I can find regarding the schema reference and several of the Garmin URLs in that sample do not even resolve:
https://en.wikipedia.org/wiki/GPS_Exchange_Format#Sample_GPX_document
The first line of the Garmin XSD file has a URL that does not resolve:
https://www8.garmin.com/xmlschemas/GpxExtensionsv3.xsd
<xsd:schema targetNamespace="">www.garmin.com/.../v3" elementFormDefault="qualified">
This is a link to the Topografix documentation. I can't find the equivalent Garmin extension documentation:
http://www.topografix.com/GPX/1/1/
Basic GPX file validation:
$ cat v1sample.gpx
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<gpx
xmlns="http://www.topografix.com/GPX/1/1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="www.topografix.com/.../1
">www.topografix.com/.../gpx.xsd"
version="1.1"
creator="gpx-poi.com">
<wpt lat="17.000000" lon="0.000000">
<time>2021-02-27T23:15:59Z</time>
</wpt>
</gpx>
$ xmllint --noout --schema http://www.topografix.com/GPX/1/1/gpx.xsd
v1sample.gpx
v1sample.gpx validates
GPX file with Garmin extension (www.garmin ==> www8.garmin for some URLs to resolve):
$ cat v3sample.gpx
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<gpx
xmlns="">www.topografix.com/.../1"
xmlns:gpxx="">www8.garmin.com/.../v3"
xmlns:xsi="">www.w3.org/.../XMLSchema-instance"
xsi:schemaLocation="www.topografix.com/.../1 www.topografix.com/.../gpx.xsd
www8.garmin.com/.../v3
">www8.garmin.com/.../GpxExtensionsv3.xsd"
version="1.1"
creator="gpx-poi.com">
<wpt lat="17.000000" lon="0.000000">
<time>2021-02-28T00:04:17Z</time>
<extensions>
<gpxx:WaypointExtension>
<gpxx:Proximity>1000</gpxx:Proximity>
</gpxx:WaypointExtension>
</extensions>
</wpt>
</gpx>
$ xmllint --noout --schema www8.garmin.com/.../GpxExtensionsv3.xsd v3sample.gpx
warning: failed to load external entity "">www8.garmin.com/.../GpxExtensionsv3.xsd"
Schemas parser error : Failed to locate the main schema resource at 'www8.garmin.com/.../GpxExtensionsv3.xsd'.
WXS schema www8.garmin.com/.../GpxExtensionsv3.xsd failed to compile