Systems and methods for identifying a location and/or an orientation of an electromagnetic (EM) sensor navigated within an EM volume are provided. Calculated EM field strengths at each gridpoint of a second set of gridpoints of the EM volume are retrieved from a memory. An EM field is generated by way of an antenna assembly. A measured EM field strength is received from the EM sensor. A first gridpoint among a first set of gridpoints of the EM volume is identified based on the measured EM field strength and a high density (HD) map. The location and/or the orientation of the EM sensor is identified based on the HD map, using the first gridpoint as an initial condition, with the second set of gridpoints also including the first set of gridpoints.
