Consider a google map which has a panel overlay allowing you to choose from certain criteria to display points on the map
You are working withing the confines of the dimensions of the map but may have multiple categories of filters that you want to display. The categories you choose are directly linked to the map so to have them seperated from the map i.e. not in an overlay would present a usability and feedback on selection challenge
In this example it would make sense to use an accordion for example you may have a local area statistics map and your accordion might be organised by
Crime Statistics
Burglaries
Wealth Statistics
Rich
Poor
I would not use an accordion as a replacement for traditional vertical navigation