Time synchronize multiple uBlox messages to get a single callback
Port of message_filters::ExactTime message synchronization policy to use integer time of week in milliseconds (iTOW) instead of ros::Time in a header.
The message_filters::ApproximateTime message synchronization policy is not relevent because messages generated by a ublox sensor for a single update contain identical iTOW time stamps.
See src/example.cpp for example usage.
Launch the example with roslaunch ublox_msg_filters example.launch. The example is not installed, so this must be in a source workspace.