First the preliminaries: Firmware: 5.30; Unit is North American version, pre-loaded with North American maps; Turn by Turn Navigation is enabled in the Rider Settings; Bluetooth and peripheral connectivity all disabled; battery saver mode is enabled; Navigate to course start refused. All tests done at the desktop.
The course being calculated is 192KM long, was created in Garmin Connect, then sync'ed to the Explore via Garmin Express.
- One Stock Garmin Map Enabled: a) AMR Standard Basemap, NR. Initial Route Calculation: 1 minute. Notes: This config ended in a Route calculation Error. Unusable.
- Two Stock Garmin Maps Enabled: a) AMR Standard Basemap, NR; b) Garmin Cycle Map Amer, North. Initial Route Calculation: 9 minutes.
- Four Stock Garmin Maps Enabled: a) AMR Standard Basemap, NR; b) Garmin Cycle Map Amer, North; c) Garmin DEM Map North America; d) Garmin Geocode Map North America. Initial Route Calculation: 9 minutes. Notes: No difference from having two maps enabled.
- One Third Party OSM Map Installed and Enabled: A Routable Bicycle Map (Openfietsmap Lite) for Ontario, Canada (downloaded from garmin.openstreetmap.nl/). Initial Route Calculation: 8 minutes.
Conclusion: Looks like 8-9 minutes is the best case reference for calculating the 192km course with TBT navigation. NOTE: This is not the Ride Settings-->Routing-->Recalculation option which is OFF in this case. (That feature really gums up the works IMO).
This is the longest course I've ridden with the Edge Explorer and the unit performed adequately however every feature that wasn't essential for the ride was disabled; it was operating in a bare bones minimalist capacity.
Addendum: It seems the onerous route calculation times are just the nature of the beast. Various active map configurations don't seem to make that much of a difference for TBT enabled courses. That leaves the hardware--can't do anything about that--and firmware. In other threads it's been noted that firmware 5.30 may be aggravating calculation times and commenters remember earlier versions to be much speedier. I'm willing to try reverting back to version 5.xx but don't know where they're archived or the installation process. Any insights?