[FOSS-GPS] Does anyone know that why RTKLIB does not support NMEA input?
dannym at austin.rr.com
Wed Oct 3 09:31:34 PDT 2012
Not only that but the NMEA I've seen doesn't even have the accuracy.
From what I saw on the NVS units, monitoring data showed approx 5"
resolution in lat/long in my location.
The binary format, however, has something like sub-cm resolution. Let me
be clear this wasn't RTK, just ordinary position fixes, and the absolute
accuracy was NOT on that scale, however, the relative accuracy and
stability of a position fix was remarkable- the point is that it looks
like they didn't represent as many digits in NMEA. AFAIK the NMEA
standard didn't dictate how many digits could be given but I have a
theory is there may be an ad-hoc standard in some NMEA parsers that
won't handle an unusually high number of digits.
NMEA isn't very compact, either.
That's the difference in reading normal fixes between binary and NMEA
formats. As Yebin says, it's irrelevant for RTK: RTK can ONLY with work
with pseudorange/carrier phase/doppler data which is NEVER present in NMEA.
Just to be be clear, there are 3 things here: NMEA and vendor-specific
binary mode are both transport formats. Raw data is additional info
which has only been presented in vendor-specific binary mode data.
Hypothetically speaking, raw data COULD be presented in NMEA in subset
of vendor-specific $prefix words, but there is little reason to do so.
On 10/3/2012 9:31 AM, Timo Juhani Lindfors wrote:
> Yebin Lee <yblee87 at gmail.com> writes:
>> I'm just wondering that why RTKLIB only support raw protocol input instead
>> of NMEA which is popularly used in common GPS receivers.
>> Is there a reason for this?
> Because NMEA does not contain pseudorange measurements?
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