>> In future a person or program using data defined as NAD83(CSRS) will
>> reasonably expect sub-meter datum accuracy, for that is the purpose of
>> the datum. if this is not the case, it should not call itself such.
>
> The accuracy of any data is irrelevant to the projection it's in though. I
> c
On Wed, Jul 29, 2009 at 9:48 AM, Matt Wilkie wrote:
> Hi Robert, thank you for contributing your insight, it helps!
>
> > cs2cs -v is quite clear about what it's doing, OGR not so much.
> >
> > Using the "straight" Proj EPSG defs on my system:
> > $ cs2cs -v +init=epsg:3579 +to +init=epsg:4617
>
Hi Robert, thank you for contributing your insight, it helps!
> cs2cs -v is quite clear about what it's doing, OGR not so much.
>
> Using the "straight" Proj EPSG defs on my system:
> $ cs2cs -v +init=epsg:3579 +to +init=epsg:4617
...
> No datum transform will happen (ellipses match, and +towgs8
On Wed, Jul 29, 2009 at 5:25 AM, Matt Wilkie wrote:
>
> Let's see if I have this straight then: if I specify -t_srs epsg:4617 and
> not
> +nadgrid, no datum transformation occurs, even though the output .prj file
> says it has?
If your projection definition in Proj4/OGR has a datum defined it w
Let's see if I have this straight then: if I specify -t_srs epsg:4617 and not
+nadgrid, no datum transformation occurs, even though the output .prj file
says it has?
-matt
Francesco P. Lovergine wrote:
>
> On Fri, Jul 24, 2009 at 09:09:27AM -0700, Matt Wilkie wrote:
>>
>> Now back to GDAL and
On Fri, Jul 24, 2009 at 09:09:27AM -0700, Matt Wilkie wrote:
>
> Now back to GDAL and related projects: does the fact that there is no proj4
> NAD83(CSRS) datum parameter mean the X-to-NAD83(CSRS) transformation is not
> happening?
>
AFAIK for Canada you can download the freely available NTv2 f
> I suspect EPSG does not define a NAD83(CSRS) datum
> because it needs a dynamic reference frame definition,
> which cannot be approximated decently with a seven parameters
> transformation, anyway. So it would be not a proper approach.
For clarity, EPSG does define a NAD83(CSRS) datum, it's
> Is there a difference between NAD83 and NAD83 CSRS ?
> (the difference between NAD83/GRS80 and WGS84/WGS84
> is usually neglectable).
I have been operating on the presumption there must be _some_ kind of
important difference else they wouldn't have gone through the bother of
formulating and es
On Thu, Jul 23, 2009 at 10:13:42AM -0700, Matt Wilkie wrote:
>
> I came across this curiosity while trying to figure out what the
> equivalent proj4 parameters were to epsg:3579. Using
> "+datum=nad83(csrs)" and combinations thereof result in
> "datum_unknown" being written to the .prj file.
> ((i
Matt,
testepsg EPSG:3579 shows : +proj=aea +lat_1=61.66 +lat_2=68
+lat_0=59 +lon_0=-132.5 +x_0=50 +y_0=50 +ellps=GRS80 +units=m
+no_defs
So it looks like it doesn't have the datum information. I think proj won't
make any datum transformation then. If your input data is alr
Hello All,
I've recently noticed that projecting with ogr2ogr (and I presume
gdalwarp since they share so much) and using epsg codes adds information
to .prj files that apparently proj doesn't know about. For example:
# ogr2ogr -f "esri shapefile" -t_srs epsg:3579 (...)
will write this .pr
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