A method for synchronizing network clocks comprising the following steps: measuring with a first magnetometer the geomagnetic field at a first network node; processing data measured by the first magnetometer to generate first sensor spatially-coherent data; measuring with a second total field magnetometer the Earth's magnetic field at a second network node, wherein the second magnetometer is physically separated from the first magnetometer by a distance of up to one kilometer; processing data measured by the second magnetometer to generate second sensor spatially-coherent data; transmitting the first sensor spatially-coherent data from the first network node to the second network node; calculating a clock drift between the first and second network nodes based on the first sensor spatially-coherent data and the second sensor spatially-coherent data; and adjusting the second node system clock to match the first node system clock based on the calculated clock drift.