Re: Getting GPS data into stream

[Marcus D. Leech]

On 03/05/2023 14:04, Marcus Müller wrote:
> Hi Fabian,
>
> I'd write a block that copies a stream in- to output. It might query 
> gpsd every time the work() function is called, or have a FIFO into 
> which data from gspd is being pushed by a separate thread (or by 
> reading from  a socket or however gspd works, I must admit I'm not sure).
>
> You then take that info, and encode the long, lat, uncertainty as 
> (double, double, double) PMT tuple. You then use add_item_tag to add 
> that PMT to the first sample in your output buffer.
>
> You'd feed the result into a metadata file sink block: That saves 
> things in a serialized format ready for retrieval.
>
> Best,
> Marcus
>
> On 5/3/23 19:52, Fabian Schwartau wrote:
> > Hi everyone,
> >
> > I am trying to record some data from an SDR and would like to 
> > sync/tag the data with the current gps position from gpsd. I am kind 
> > of stuck and don't know how a possible solution for that might look 
> > like in grc.
> > I have a python function that gets the current position as a tuple, 
> > but how do I get this into my data stream, which I would like to 
> > write to a CSV file or similar?
> > I am not asking for a solution of my problem, just point me in the 
> > right direction ;)
> >
> > Best,
> > Fabian
Quite apart from the GPSD-specific stuff, it would be useful to have a 
kind of "annotated formatted data" file sink for low-rate
  data (like scientific data, etc) which supports CSV outputs, and has 
some way of ordering any tags that come in with the
  data and formatting them appropriately, but still be reasonably 
"generic"  (in that the block doesn't really *know* anything
  about the tags, and can be told how to format them).  Maybe *in 
addition* you could pass the block a series of methods to
  call at some configurable cadence.

This somewhat overlaps with what SigMF tries to do, but this is 
formatted data, inherently low-rate, with formatted
  annotations.

I nearly always end up doing this in a custom way for my applications, 
but having a generic block would be cool, and not
  hard to do.   Could be entirely in Python, since we're talking "low 
rate" (like perhaps a few per second at most).