Plans for Copernicus II?

Hey SparkFun, are you folks planning on updating your [Copernicus DIP Module with the Copernicus II? The II is pin-compatible with the I; it just adds Vbat, which isn’t required (but should probably be tied to VCC). That pin is brought out with the breakout board anyhow. I’ve extracted some of the critical stats from the [Copernicus I and [Copernicus II spec sheets:

       I      II
freq   1      1      Hz
power  31     44     mA (3.0V)
track  -152   -160   dBm
aquis  -142   -144*  dBm
hot    9      8**    s
warm   35     35     s
cold   39     38     s
PPS    +/-50  +/-350 ns
horiz  <3     <2.5   m         (50% of the time)
  90%  <8     <5     m
alt    <10    <5     m         (50% of the time)
  90%  <16    <8     m

* -148 dBm if hotstart with emphemeris
** 3s with battery backup

If SFE won’t be supplying the Copernicus II anytime soon, would I be able to order two Copernicus DIP boards populated with everything but the GPS module?

I’m working on implementing differential GPS by buying two identical modules and using one as a base station. The Copernicus series modules have the option to output 64-bit floating point lat/long, while NMEA output generally has resolution on the order of ~24cm (calculated at 34deg latitude, by taking the distance between a point and the point with both lat and long incremented by the smallest amount possible). What I’m hoping is that 64-bit floating point values will give me much better resolution than standard NMEA output and even better resolution than devices which output 32-bit signed integers scaled by 1e-7 (resultant resolution: 1.44cm). Note that I’ll be subtracting the coordinates I obtain from both units at a given time step, which should remove ephemeris and atmospheric propagation errors. The units will generally be within a km of each other, so I’m hoping to get sub-cm accuracy & precision.](http://trl.trimble.com/docushare/dsweb/Get/Document-501977/022542-012D_63530_00_Copernicus-II_DS_0211_US.pdf)](http://trl.trimble.com/docushare/dsweb/Get/Document-446384/Copernicus_DS.pdf)](Copernicus DIP Module - GPS-08146 - SparkFun Electronics)

labreuer:
I’m working on implementing differential GPS … Note that I’ll be subtracting the coordinates I obtain from both units at a given time step, … I’m hoping to get sub-cm accuracy & precision.

Hi,

this will only work as long as both base-station and remote are using the same set of satellites to compute their respective positions. Generally this is not the case. A proper differential implementation uses 1st and 2nd order corrections to pseudoranges from each satellite, among others. See RTCM-104

Thanks. I’m aware of the requirement that the # of SVs be the same, although I’d like to see how big a deal a one-SV difference is. (Alas, I’m not sure I’m up to doing this via theory, only experiment.) I also may be able to force the receivers to use a common set of SVs by lying about health statuses of SVs that are not in common between the two units – the Copernicus unit allows one to send it almanac/ephemeris/health/etc.