Second question first, you don't say which nuvi? On some avoidances can be set, on others they can't. Either way I don't know if avoidances set in Basecamp will be sent to a nuvi.
As to adding avoidances within Basecamp, yes in the latest versions. To show the relevant icon in the toolbar go to View, Toolbars, Area Avoidances and select it. You'll then see the icon in the toolbar.
My Devices are in my Signature, but my Nuvi has the option to add Road Avoidances but it's a bit difficult to add those.
I have tried the avoidances in basecamp and they indeed work and will test some more if they also get send to the device.
One thing I already noticed, it could be very handy if you could rename the Avoidance Area in Basecamp as the name "Area Avoidance" and "Area Avoidance 1" are not really that helpful ;)
Another one which could handy, is the ability to resize the area, as you now have to delete the area and create it again.
I love this feature, because some of the roads in the area are in a REALLY (I MEAN REALLY) (sorry for the All Caps) bad shape, and my GPS always wants to send me that way. :rolleyes:
I did some test and it seems the Avoidances you set in BaseCamp aren't transferred to the GPS.
What IMHO you can do is, that you create routes in BaseCamp (with Avioidances in place) and send that Route to your GPS with the Avoidances (you have set in BaseCamp) in place.
So if you create a Route in your GPS (Tripplanner for example) the GPS only looks at Custom Avoidances you have created in the GPS. So this BaseCamp feature is only (again IMHO) useful if you create routes and not for ad hoc Navigation.
A Shame really, it could be a real useful feature (especially for me :cool:)
Every GPS device is a little different and they all support different features. Most GPS devices that accept routes should follow the route as calculated on the device as was done on BaseCamp.
In talking with our tech lead for BaseCamp, we do have the area avoidences tool where you can highlight an area and set it as an avoidance. Since all of the maps are a little different this was a good generic way to avoid certain locations in map calculations.