[time-nuts] OT [GPS Survey grade RX]

[bg at lysator.liu.se]

> When you start getting to less than a meter.. For absolute, you need to
> start worrying about stuff like solid earth tides, plate movement, a whole
> host of things are all contributors in that 10-100 cm range.

Absolute and relative... can be a word game. It depends what DATUM
(coordinate system) you want to have your answer in.

> For precision attitude, e.g gun laying, differential carrier phase works
> pretty well, but consider what sort of phase measurement performance is
> needed over a say one meter baseline with 20cm wavelength.

The below datasheet mentions 0.22deg/m baseline. You need decent antennas
and limited multipath to get there.

   http://javad.com/downloads/javadgnss/sheets/DeltaD_Datasheet.pdf

There are also some quotes on relative positioning performance.

> On Dec 5, 2010, at 11:31 AM, Brooke Clarke <brooke at pacific.net> wrote:
>
>> Hi Brian:
>>
>> A friend has an Android cell phone with built in GPS.  It has a
>> resolution of 0.0001 arc seconds as does the GPS I just got for my
>> camera:

The lat/lon resolution is fairly unimportant as long as it resolves
enough.  Neither the antenna nor the receivers used in cell phones are
good for better than a few meters in positioning accuracy.

--

    Björn