[Proj] lat/long format question

[Roger Oberholtzer]

On Fri, 2009-10-30 at 17:22 +0100, OvV_HN wrote:
> ----- Original Message ----- 
> From: "Roger Oberholtzer" <roger at opq.se>
> To: "PROJ.4 and general Projections Discussions" <proj at lists.maptools.org>
> Sent: Friday, October 30, 2009 1:09 PM
> Subject: Re: [Proj] lat/long format question
> 
> 
> ....
> 
> > My data is a third representation:
> >
> > 3.5 in dd.ddd is 330.0 in ddmm.mmmm
> > 43.5 in dd.ddd is 4330.0 in ddmm.mmmm
> >
> > The ddmm.mmmm format is how Trimble receivers provide lat/long values in
> > NMEA GGA records, while the dd.dddd format is what Garmin receivers
> > provide in their NMEA GGA records.
> 
> 
> Ah! I didn't realise such a format was among the actually used ones.
> Shouldn't the EPSG database list this format in the section 
> epsg_unitofmeasure?

I come across dd.dd ddmm.mm and ddmmss.ss

Frank reminded me that it is radians that I am passing. Of course this
is the case. Too much to keep track of. And, it is Friday (and a partial
holiday in Sweden).

So the answer to my question is that I must arrange dealing with this
outside proj4. Which I am fully in agreement with.

> Or is it a proprietary format, only used by Trimble?

I cannot say. I would be curious to know what is the most common. I
think the NMEA standard states ddmm.mm. So I think it is the Garmin that
is non-standard. Even if it is very common. We have always used Trimble.
And Applanix. I will have to check what we are doing with Applanix data.
The Garmin experiment is for those of our users not requiring accuracy
beyond some meters.

> Anyhow, wouldn't it be more productive if the PROJ command line had a flag, 
> denoting the format of the DMS input and output?

For data arriving at the library via that route, perhaps. My use is via
the C API in an application that tracks locations in real time. We use
the library direct, providing radians.

-- 
You can't just ask customers what they want and then try
to give that to them. By the time you get it built, they'll
want something new.  -- Steve Jobs

Roger Oberholtzer

Ramböll RST/OPQ

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