What is the maximum value of the Satellite's Signal Strength?

Question

From the documentation of GPS_POSITION,

rgdwSatellitesInViewSignalToNoiseRatio

Signal to noise ratio of the satellites in view of the GPS hardware. Higher numbers indicate greater signal strength.

I tried to retrieve the Satellite ID and the Signal Strength and here is the result

    ID    Signal Strength
   ______________________
     1         21
    23         18
    19         12
    20         18
     3         12
    32         14
    13         15

Question is, is there a fixed maximum value of Signal Strength? If yes, then what is the value?

The purpose is I want to display the signal strength for each satellites in percentage form (as my client want to see) such as below:

    ID    Signal Strength
   ______________________
     1         21 % ?
    23         18 % ?
    19         12 % ?
    20         18 % ?
     3         12 % ?
    32         14 % ?
    13         15 % ?

Usually signal strength is given in dB, as the distance between the noise floor and the signal. So the value depends on how prevalent the noise is and how strong the signal is above that. Theoretically I don't think there is a maximum value, but given the structure it's safe to say it will fit in a `DWORD` :-). (And I just learned that GPS actually has a *negative* SNR at the antenna level which needs quite a bit of trickery to coax the signal out of that so much louder noise.) — Joey, Jun 10 '14 at 08:22
@Јοеу I've added some info in my question. but if what you are saying is correct, then I guess I have no way out huh. — Baby, Jun 10 '14 at 08:32
You could watch the numbers and just assume something slightly below the maximum as your cut-off point for 100 %. Or use other measures, as detailed by [this question](http://stackoverflow.com/q/3159260/73070) — Joey, Jun 10 '14 at 10:17

score 1 · Accepted Answer · edited May 23 '17 at 10:10

Signal strength is the distance between the noise and the signal itself (and, in case of GPS it's actually negative at the antenna). So depending on how good the satellite reception is, how the receiver boosts the signal and how much noise you have, the numbers will vary. Also there isn't exactly a hard upper limit as it depends on the factors mentioned above. Things you could do here

Measure the signal strength over some time and keep note of the maximum numbers that appear. Take that as your 100 % measurement (or something slightly lower, as good reception is enough and you don't necessarily need awesomely great reception). And don't forget to clamp the percentage to 100.
Use a different measurement, like mentioned in this question, especially this answer. The DOP is essentially the GPS receiver's way of measuring the accuracy of the position it gives you. It's not exactly signal strength, but more a confidence how accurate the position is.

What is the maximum value of the Satellite's Signal Strength?

1 Answers1