There are a couple of aspects with a route spanning more than one UTM zone to be kept in mind.
First of all, TransDEM fully supports route building across UTM zone boundaries. Most of the handling is automatic, too.
Mathematically, any TransDEM route must lie in a single UTM zone. We will call it the primary zone. To accomplish this, this primary zone can be made wider than originally defined by the UTM coordinate system. Any geo data from an adjacent zone must be converted to the coordinates of the primary zone.
The primary zone should be the one with the most track.
The easiest way to convert between zones is to use the DEM and the TransDEM function "Convert UTM zone". The DEM loaded determines the zone.
A DEM composed from from smaller DEM clippings, using the TransDEM "Add DEM" function will always be merged into the UTM zone of the first DEM.
Hint: If DEM resolution is high, zone conversion will take significant time. To speed up for the purpose of zone switching, re-sample the DEM to a much lower resolution like 250m ("New DEM Raster Width") and use this DEM for all UTM zone activities.
Now for the map clippings:
MS Research Maps require coordinates in the native zone range. If the WMS returns the Great White Void or yields an error message, switch to the adjacent zone via the "Convert UTM zone" function (DEM must be loaded). Then access the WMS again. This way you will get georeferenced map clippings from both the primary and secondary zone, but don't worry.
Once a DEM has been loaded in TransDEM, existing georeferenced map clippings or vector data from adjacent UTM zones will be converted automatically when opened on top of the current DEM.
MS Research Map clippings will show white margins beyond UTM zone boundaries. These can be edited manually in TransDEM using the relatively new "Transparent Margins" function. Note that there will usually be a small residual map error where the zones meet.
I hope this helps.
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