[GRASS-dev] [GRASS GIS] #2456: read CSV from GDAL data directory

[Helena Mitasova]

I suggest to treat it as a separate datum, the coordinates would be
different although the differences are for most applications negligible.
With the sub-meter resolution data now quite common it is important to
treat it as different.
 See more info here:
http://www2.arnes.si/~gljsentvid10/datm_faq.html#1.2
https://confluence.qps.nl/pages/viewpage.action?pageId=29855153
http://www.ngs.noaa.gov/faq.shtml#WhatHARN

Just to make things more complicated a committee was set up in NC to decide
how to deal with upcoming dynamic datum with more frequent updates.

Helena

On Mon, Apr 25, 2016 at 10:47 PM, Markus Neteler <neteler at osgeo.org> wrote:

> (cc Helena)
>
> First of all, thanks to Even and Paul to shed some light on this!
>
> On Mon, Apr 25, 2016 at 10:37 PM, Paul Kelly
> <paul-grass at stjohnspoint.co.uk> wrote:
> ...
> > The problem is actually even simpler (datum simply not recognised in
> GRASS)
> > and there are two possible solutions:
> >
> > 1) If we want NAD83_High_Accuracy_Reference_Network to be treated as a
> > completely separate datum from North_American_Datum_1983, then we add it
> as
> > a new line in lib/gis/datum.table as per the first attached patch.
> >
> > 2) If we want NAD83_High_Accuracy_Reference_Network to be treated as
> > equivalent to North_American_Datum_1983 (this means once the location has
> > been created, 'g.proj -w' will report the datum name as
> > North_American_Datum_1983), then we add two new lines to the equivalent
> > pairs array in lib/proj/convert.c as per the second attached patch.
> >
> > I don't really feel qualified to decide which is the most desirable
> > behaviour, so I'll leave that up to someone else to decide, if that's OK.
>
> I also don't feel too qualified here :) but from a user's point of
> view a change of name is confusing.
>
> So option 1) looks better to me (i.e., " datum.table.patch") which is
> tested ok here.
> Maybe Helena as our NC expert has an opinion here?
>
> Paul, still struggling with "SIRGAS2000"
> https://trac.osgeo.org/grass/ticket/2456#comment:15
> (g.proj versus testepsg output). Needs a different trick?
>
> Markus
>
>
> --
> Markus Neteler
> http://www.mundialis.de - free data with free software
> http://courses.neteler.org/blog/
>



-- 
Helena Mitasova
Professor
Department of Marine, Earth and Atmospheric Sciences
North Carolina State University
1125 Jordan Hall
NCSU Box 8208
Raleigh, NC 27695-8208
http://www4.ncsu.edu/~hmitaso/
http://geospatial.ncsu.edu/

email: hmitaso at ncsu.edu
ph: 919-513-1327 (no voicemail)
fax 919 515-7802
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