not the same meas- urement, and their respective acceptable range of values is very different from each other. SNR is usually expressed in terms of decibels. It refers to the ratio of the signal power and noise power at a given bandwidth. Those power values are expressed either as decibel-milliwatts (dBm, sometimes dBmw) or decibel-watts (dBW). Note that for satellite reception, the SNR is negative, which means that the signal power is much less than the noise, which is why acquiring the signal is a complex and sensitive process. C/No, on the other hand, is usually expressed in decibel-hertz (dB-Hz) and refers to the ratio of the carrier power and the noise power per unit bandwidth. Confusingly, some GNSS receivers call the signal strength values "SNR" but report C/No numbers. There are some typical ranges of expected values for reception of GPS L1 coarse/acquisition (C/A) signals. A reasonable receiver would expect to receive signals in the range of ~ 37 to 45 dB-Hz C/ No, which is roughly equivalent to an SNR of ~ -29 dB to -21 dB (a higher negative dB number is a weaker signal). The amount of data that a receiver can decode from signals begins to drop very sharply when it is less than 35 dB-Hz. There are multiple stages in the state of a GPS receiver. In the acquisition phase, the receiver is try- ing to detect and acquire the satellite signal from among the noise. After the receiver has acquired the satellite signal, it moves to the tracking loop. Once the tracking has begun, the receiver can (slowly) receive the time and navigation data and start to calculate a solution for location (in three dimensions) and time. Most receivers determine the location and average the solution for position over time (to arrive at a more accurate position). Finally, when the receiver decides that it has de- termined the position to sufficient accuracy, it switches to a timing mode (a more accurate value for location improves the accuracy of the time). A problem arises if the antenna has only a limited view of the sky or is suf