[Qgis-user] NTV2 Grid Shits

[Tyler Veinot]

Since you guys both know more about PROJ4 than I do I thought I would just
tag this question on;
Where is QGIS/PROJ4 with support for vertical datums? Is there a way I can
attach a vertical datum to a CRS in PROJ4?
Tyler

On Mon, Oct 23, 2017 at 9:09 AM, Tyler Veinot <tylerkveinot at gmail.com>
wrote:

> Andre;
> It seems QGIS does not like my gsb file, I downloaded the NTV2 gsb from
> NRCan and pointed to it and it worked. For some reason the one specific for
> PEI does not. However, the grid shift could be the same as far as I know;
> cannot find any information on what mathematical principles are used to
> define the shift to correct the coordinates.
> Tyler
>
> On Mon, Oct 23, 2017 at 8:01 AM, André Joost <andre.joost at arcor.de> wrote:
>
>> Am 20.10.2017 um 20:19 schrieb Tyler Veinot:
>>
>>> Andre;
>>> Again, sorry accidently sent the email mid writing. Where was I....
>>> Right so I added
>>>
>>> nadgrids=PE7783V2.gsb a number of ways trying to sort it based on online
>>> information and how some other CRS's were setup within QGIS but nothing
>>> worked yet.
>>>
>>
>> It might be better to post the full string.
>>
>>
>> When I add the directory to my gsb where do I add it in the line and does
>>> it need quotes?
>>>
>>
>> If you have blanks in folder names, surely.
>>
>> HTH,
>> André Joost
>>
>>
>>
>>>
>>> On Fri, Oct 20, 2017 at 2:55 PM, Andre Joost <andre+joost at nurfuerspam.de
>>> >
>>> wrote:
>>>
>>> Am 20.10.2017 um 14:31 schrieb Tyler Veinot:
>>>>
>>>> Anyone knowledge in using grid shift files (gsb) with QGIS?
>>>>> I have a local CRS NAD27 Double Stereographic Imperial that I need to
>>>>> transform to NAD83 CSRS 2010 Epoch. I have the CRS properly defined
>>>>> using
>>>>> the provincial description
>>>>>
>>>>>
>>>> Can you add your custom CRS? Maybe you have +datum=nad27 which uses the
>>>> main nadcon transformation file. use +ellps=clrk66
>>>> +nadgrids=/path/to/your/file
>>>>
>>>>   but QGIS using its Clark 1866 to GRS80
>>>>
>>>> transformation puts the points a little off from the NTV2 coordinate
>>>>> transformation software we have. I have the GSB used (even though it
>>>>> says
>>>>> ATS77 the provincial geomatics guys tell me it shits NAD27 and ATS77
>>>>> into
>>>>> CSRS 2010 NAD83). I followed some directions on putting the file in a
>>>>> specific folder and restarted QGIS set the settings to always ask for
>>>>> grid
>>>>> shift file for transformations yet I do not see the one I put in there
>>>>> in
>>>>> my list to pick from.
>>>>>
>>>>>
>>>> Can you explain where that setting should be?
>>>>
>>>>
>>>> I also tried to install a plugin for NTV2 transformations but cannot
>>>>
>>>>> activate it. When I go to Activate Additional Providers in my
>>>>> Processing
>>>>> Toolbox where NTv2 Datum Transformations resides I get the "Specified
>>>>> Path
>>>>> does not exist: C:\PROGA~1\QGIS~1.18\bin" error that I have not yet
>>>>> managed
>>>>> to resolve. To my understanding has something to do with GRASS plugins
>>>>> and
>>>>> past versions of QGIS.
>>>>>
>>>>>
>>>> You can workaround that GRASS error by creating that folder, or changing
>>>> the folder entry for GRASS 7 to an existing folder.
>>>> But to use your grid in the plugin, you would need some python code
>>>> around
>>>> it, like the other grids have in C:\Users\<username>\.qgis2\pyt
>>>> hon\plugins\ntv2_transformations
>>>> Without that processing would not know about your grid.
>>>>
>>>> HTH,
>>>> André Joost
>>>>
>>>>
>>>>
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>>>>
>>>
>>
>>
>
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