A system for providing differential corrections for positioning, the system comprising: a roving reference device that is arranged to be aware of its geographic location, the RRD comprising: a RRD receiver for receiving a signal, at a first receive time, from at least one low earth orbiting or terrestrial transmission source, wherein the RRD is arranged to be aware of a location of the at least one transmission source, a RRD clock for collecting a first measurement of the signal, a RRD memory for storing the first measurement, a RRD processor for processing, for multiple positions of the at least one transmission source, the first measurement, the location of the RRD, and the location of the at least one transmission source to generate differential correction information comprising a difference between the first receive time and an initial time, wherein the initial time represents a time that the RDD would have received the signal sent at a particular time if there were no delays, wherein the initial time is calculated from a known range between the at least one transmission source and the location of the RRD, and a RRD transmitter for transmitting a differential correction information signal that includes the differential correction information; and a receiving device comprising: a RD first receiver for receiving the signal from the at least one transmission source, wherein the RD is arranged to be aware of the location of the at least one transmission source, a RD clock for collecting a second measurement of the signal, a RD memory for storing the second measurement, a RD second receiver for receiving the differential correction information signal from the RRD, and a RD processor for processing, for multiple positions of the at least one transmission source, the differential correction information, the second measurement, and the location of the at least one transmission source to generate a location estimate for the RD. a roving reference device that is arranged to be aware of its geographic location, the RRD comprising: a RRD receiver for receiving a signal, at a first receive time, from at least one low earth orbiting or terrestrial transmission source, wherein the RRD is arranged to be aware of a location of the at least one transmission source, a RRD clock for collecting a first measurement of the signal, a RRD memory for storing the first measurement, a RRD processor for processing, for multiple positions of the at least one transmission source, the first measurement, the location of the RRD, and the location of the at least one transmission source to generate differential correction information comprising a difference between the first receive time and an initial time, wherein the initial time represents a time that the RDD would have received the signal sent at a particular time if there were no delays, wherein the initial time is calculated from a known range between the at least one transmission source and the location of the RRD, and a RRD transmitter for transmitting a differential correction information signal that includes the differential correction information; and a RRD receiver for receiving a signal, at a first receive time, from at least one low earth orbiting or terrestrial transmission source, wherein the RRD is arranged to be aware of a location of the at least one transmission source, a RRD clock for collecting a first measurement of the signal, a RRD memory for storing the first measurement, a RRD processor for processing, for multiple positions of the at least one transmission source, the first measurement, the location of the RRD, and the location of the at least one transmission source to generate differential correction information comprising a difference between the first receive time and an initial time, wherein the initial time represents a time that the RDD would have received the signal sent at a particular time if there were no delays, wherein the initial time is calculated from a known range between the at least one transmission source and the location of the RRD, and a RRD transmitter for transmitting a differential correction information signal that includes the differential correction information; and a receiving device comprising: a RD first receiver for receiving the signal from the at least one transmission source, wherein the RD is arranged to be aware of the location of the at least one transmission source, a RD clock for collecting a second measurement of the signal, a RD memory for storing the second measurement, a RD second receiver for receiving the differential correction information signal from the RRD, and a RD processor for processing, for multiple positions of the at least one transmission source, the differential correction information, the second measurement, and the location of the at least one transmission source to generate a location estimate for the RD. a RD first receiver for receiving the signal from the at least one transmission source, wherein the RD is arranged to be aware of the location of the at least one transmission source, a RD clock for collecting a second measurement of the signal, a RD memory for storing the second measurement, a RD second receiver for receiving the differential correction information signal from the RRD, and a RD processor for processing, for multiple positions of the at least one transmission source, the differential correction information, the second measurement, and the location of the at least one transmission source to generate a location estimate for the RD.