Gelderland as a German floating flak platform

How did the former Dutch cruiser Gelderland serve as an anti-aircraft ship?

Germany converted her into Niobe, a slow mobile flak platform able to bring a self-contained air-defense battery and its support infrastructure to coastal positions.

The converted protected cruiser was slow but could carry and sustain a substantial anti-aircraft battery. Its 16-knot speed mattered less when the mission was to reinforce coastal and harbour defences. Its value lay in moving an integrated package of weapons, rangefinding, ammunition, crews, and support to a defended position. That floating flak role differed from the work of a fleet screening cruiser.