1. A method for collaborative navigation, comprising: (a) initializing a conditionally independent filter on a local platform; (b) propagating the conditionally independent filter forward in time; (c) when a local measurement has been made, updating the conditionally independent filter with the local measurement; (d) when a common measurement has been made, updating the conditionally independent filter with the common measurement; (e) determining by a processor whether a remote conditioning node has arrived from a remote platform for conditional update processing; (f) if a remote conditioning node has arrived, determining by the processor whether the remote conditioning node needs to be fused with a first local conditioning node of the conditionally independent filter; (g) if the remote conditioning node needs to be fused with the first local conditioning node, performing a node-to-node fusion in the conditionally independent filter to merge the remote conditioning node with the first local conditioning node to produce a merged conditioning node; and (h) performing a conditional update of the conditionally independent filter.