Prune GPS tool

You can see the GPX definition of trackpoint here (it is called wptType indeed): http://www.topografix.com/gpx/1/1/#type_wptType.

There are many fileds, but with some recent GPS loggers they are not sufficient, the GPX standard has the extensions tag for this.

I used it to save all data from loggers based on the MTK-chip, in the MTKBabel program I wrote. Here an example:

<trkpt lat="43.870960738" lon="11.083820076">
  <ele>60.971478</ele>
  <time>2009-10-15T09:00:40Z</time>
  <type>DISTANCE</type>
  <fix>3d</fix>
  <sat>9</sat>
  <extensions>
    <mtk:wptExtension>
      <mtk:valid>sps</mtk:valid>
      <mtk:satinview>10</mtk:satinview>
    </mtk:wptExtension>
  </extensions>
</trkpt>

So I think that the best approach is to keep the entire XML in memory (parsed with some library) and use (lat, lon, ele, time) as a primary key to mantain the link from Prune points to the XML structure.