[MetaCRS] Datum Transformation Issues

[Richard Greenwood]

On Wed, Feb 22, 2017 at 12:21 PM, Nick Fordes <nick.fordes at locusview.com>
wrote:

> Yes -
>
> I am hoping to achieve a sub-meter transformation between the two datums.
> Also - we would ideally like to go from ITRF 2008 to Is Proj4js an
> appropriate tool to do this?  Can it handle a grid shift transform?
>

proj4js does not support grid shift transformations. Proj4 does but the
epsg codes don't always reference the grid shift files. The Proj4 North
American grid shift files that I'm aware of are tied to State Plane
coordinate systems. I'm not aware of a grid shift file(s) covering the
whole continent, which is what it looks like you're wanting?

Rich



> Thanks,
>
> Nick
>
>
> On Wed, Feb 22, 2017 at 1:02 PM Richard Greenwood <
> richard.greenwood at gmail.com> wrote:
>
>> On Wed, Feb 22, 2017 at 10:26 AM, Nick Fordes <nick.fordes at locusview.com>
>> wrote:
>>
>> Hi -
>>
>> I am using the Proj4js library and am having trouble successfully
>> transforming coordindates from ITRF 2008 (EPSG:5332) to NAD83 (2011)
>> (EPSG:6317).
>>
>>
>> Are you getting an error or incorrect results? The espg definitions for
>> 5332 and 6317 are the same (see below) but that's not to say they are
>> correct.
>>
>> # ITRF2008 <5332> +proj=geocent +ellps=GRS80 +units=m +no_defs  <>
>> # NAD83(2011) <6317> +proj=geocent +ellps=GRS80 +units=m +no_defs  <>
>>
>>
>> I have bee successful in entering coordinates into the following tool and
>> generating results for going from WGS83 (EPSG4326) to NAD83 (2011)
>> (EPSG:6317), however, there is no transformation applied.
>>
>>
>> "NAD" datums are tied to the North American continental plate, "WGS"
>> datums are tied to the center of the earth. To get meter or sub-meter
>> accuracy transformations you need to use a grid shift transform. Is that
>> what you're looking for when you say that no transformation is applied?
>>
>>
>>
>>
>> --
>> Richard W. Greenwood, PLS
>> www.greenwoodmap.com
>>
>


-- 
Richard W. Greenwood, PLS
www.greenwoodmap.com
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