Re: Miniature GPS module with 10Hz update rate

On Fri, 22 Apr 2005 21:00:50 +0200, Rene Tschaggelar wrote:

> Mook Johnson wrote:
>
>> I need a small ~(1"x1") OEM GPS modue that runs off 3.3V and can supply a
>> new speed output at a rate of at least 5Hz, 10Hz would be more desirable.
>> I'm not interested in position inforation at this time.
>>
>> This will be used in a embedded system and feed a small microprocessor for
>> further processing.
>>
>> There are many that can output at 1Hz but I need 5 - 10Hz for best
>> performace in this application.
>
> It is not the module that provides the 1 Hz but the GPS system.
> There is just not more data. Except for those using the military
> version. I have no idea how precious these parts are nowadays,
> but at least for now you should forget them.
>
> The reason why the current commercial GPS is not delivering
> more updates ? Even kids could build a cruise missile or similar.
>
> Rene

It is completely untrue that the GPS system doesn't provide enough
information to update (especially speed) more than once per second. The
GPS unit can get the speed directly from Doppler on the various
satellites, and it can (in principle) compute Doppler shift before
it even decodes the messages.

I searched using Google with the terms "gps," "update," and "rate," and
found several links in the first result page to non-military GPS's with a
5 Hz update rate. They are not OEM units like the OP is looking for, but
this result disproves your assertion that 1 Hz is a system limitation.

There ARE export restrictions on some GPS units, but as far as I know,
the export restrictions only apply when the unit has high altitude, speed,
and acceleration envelopes.

Selective availability, AFAIK, has been turned off for several years, and
anyway I don't think it had anything to do with update rate.

--Mac

.

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