On 04/25/2016 09:12 PM, Even Rouault wrote:
Le lundi 25 avril 2016 22:02:20, Paul Kelly a écrit :
[...]
Perhaps there is a better / more correct way to get the co-ordinate
system definition from GDAL than by requesting it as a "+init=epsg:XXXX"
PROJ string?
Yes, if you use OSRImportFromProj4(), the building of the SRS WKT will be done
by "reverse engineering" the proj.4 string that gets expended by proj.4 from
+init=epsg:3358 to "+proj=lcc +lat_1=36.16666666666666
+lat_2=34.33333333333334 +lat_0=33.75 +lon_0=-79 +x_0=609601.22 +y_0=0
+ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs". Which has lost any
datum name.
The solution is simple : use OSRImportFromEPSG(hSRS, code)
Ah, thanks for the hint - but I had got confused: g.proj has actually
been using OSRImportFromEPSG() for a long time (since r31652, in 2008
actually). Faulty memory on my part.
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.
Paul
--- lib/gis/datum.table (revision 68305)
+++ lib/gis/datum.table (working copy)
@@ -36,6 +36,7 @@
nad27 "North_American_Datum_1927" clark66 dx=-22.0 dy=157.0 dz=176.0
# North American 1983
nad83 "North_American_Datum_1983" grs80 dx=0.0 dy=0.0 dz=0.0
+nad83harn "NAD83_High_Accuracy_Reference_Network" grs80 dx=0.0 dy=0.0 dz=0.0
# Tokyo datum mean
tokyo "Tokyo" bessel dx=-148 dy=507 dz=685
# Ordnance Survey of Great Britain (1936)
--- lib/proj/convert.c (revision 68305)
+++ lib/proj/convert.c (working copy)
@@ -791,6 +791,8 @@
"Sistema_de_Referencia_Geocentrico_para_America_del_Sur_2000",
"ITRF_1992",
"ITRF92",
+ "NAD83_High_Accuracy_Reference_Network",
+ "North_American_Datum_1983",
NULL
};
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