Jody Garnett ha scritto:
> On 13/06/2010, at 5:19 PM, Andrea Aime wrote:
>
>> My guess is that anybody using a CRS with DMS unit is actually storing
>> the data in decimal deegrees, and that providing actual support for
>> the DMS unit transformation would just result in confused users.
>>
>> 2150 is one of such codes, if I look at spatialreference.org they
>> are using deegree as well:
>> http://www.spatialreference.org/ref/epsg/2150/html/
>
> I hate making assumptions with any of this stuff; any way to contact the
> spatialreference.org (or proj?) about this assumption to see if it common?
They publish straight the postgis srs tables:
select srtext from spatial_ref_sys where srid = 2150;
PROJCS["NAD83(CSRS98) / UTM zone 17N
(deprecated)",GEOGCS["NAD83(CSRS98)",DATUM["NAD83_Canadian_Spatial_Reference_System",SPHEROID["GRS
1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],TOWGS84[0,0,0,0,0,0,0],AUTHORITY["EPSG","6140"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9108"]],AUTHORITY["EPSG","4140"]],UNIT["metre",1,AUTHORITY["EPSG","9001"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",-81],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",0],AUTHORITY["EPSG","2150"],AXIS["Easting",EAST],AXIS["Northing",NORTH]]
postgis=# select srtext from spatial_ref_sys where srtext like '%dms%';
srtext
--------
(0 righe)
postgis=# select srtext from spatial_ref_sys where srtext like '%DMS%';
srtext
--------
(0 righe)
The units come directly from what proj supports, which is either an
angle or:
km 1000. Kilometer
m 1. Meter
dm 1/10 Decimeter
cm 1/100 Centimeter
mm 1/1000 Millimeter
kmi 1852.0 International Nautical Mile
in 0.0254 International Inch
ft 0.3048 International Foot
yd 0.9144 International Yard
mi 1609.344 International Statute Mile
fath 1.8288 International Fathom
ch 20.1168 International Chain
link 0.201168 International Link
us-in 1./39.37 U.S. Surveyor's Inch
us-ft 0.304800609601219 U.S. Surveyor's Foot
us-yd 0.914401828803658 U.S. Surveyor's Yard
us-ch 20.11684023368047 U.S. Surveyor's Chain
us-mi 1609.347218694437 U.S. Surveyor's Statute Mile
ind-yd 0.91439523 Indian Yard
ind-ft 0.30479841 Indian Foot
ind-ch 20.11669506 Indian Chain
See also:
http://osdir.com/ml/gis.mapserver.user/2004-04/msg00759.html
>> What about:
>> a) go down and just change the current behavior to just use
>> decimal degrees. Rationale: CRS with DMS are not usable anyways,
>> so we don't have backwards compatibility issues from that pov
>
> Any way we can only do that when lenient is true?
>
>> b) alternatively, add a flag to control the DMS/degree behavior.
>
> I would prefer to add a flag; even if the default value is true.
Cool. Any reasoning behind the preference?
Cheers
Andrea
--
Andrea Aime
OpenGeo - http://opengeo.org
Expert service straight from the developers.
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