Have worked out how to edit GPX traces before uploading using JOSM. This is useful if your trace contains unnecessary waypoints or nodes, or you've inadvertently identified where you live by leaving the unit switched on from the start.

To alter GPX traces

• Start JOSM
• Click the 'Open' button on the toolbar
• Change the file selector from .OSM to .GPX and locate your GPX file
• When the file displays, right click on the file in the 'Layers' window and select 'Convert to Data Layer' from the context menu.
• Press OK to accept the warning message that pops up.
• The GPX layer is converted to a JOSM editable layer. You can now edit it.
• CAUTION. It is very easy to accidentally move the whole trace out of position by inadvertently selecting all points and dragging.
• Use the 'Select' and 'Delete Nodes' tool to remove portions of the track in bulk, or zoom in and move delete individual nodes as necessary.
• When you have finished, right click on the converted layer in the 'Layers' window and select 'Export to GPX...' from the context menu.
• Give the new file a name and press OK. Set the 'Export options' as you want, or leave. Press the 'Export and Save' button.
• This new GPX trace can be uploaded to OSM.
• The converted layer in JOSM can be deleted.