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 <[email protected]> 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 > <[email protected]> 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: [email protected] ph: 919-513-1327 (no voicemail) fax 919 515-7802
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