[Qgis-user] Upsampling TIN

[Saber Razmjooei]

Hi,

If you want to see your TIN as raw data, without interpolation and
conversion to gridded format, best to have it supported as a "mesh layer":
https://docs.qgis.org/3.4/en/docs/user_manual/working_with_mesh/mesh_properties.html

To add support for it, you need to have it in MDAL:
https://github.com/lutraconsulting/MDAL/

There are processing tools to convert it to regular vector or raster (at
user-defined resolution), but you should be able to work with the native
nodes/edges/surfaces directly from QGIS.

Regards
Saber

On Fri, 4 Oct 2019 at 18:09, Falk Huettmann <fhuettmann at alaska.edu> wrote:

> Hi,
> I agree with Barend and Nicolas here.
>
> It's a typical and essential question that we get all the time, like,
> can we re-grid and subsample pixels ?
> =>You can, technically, but you stay just within the same data,
> and thus, create nothing new or meaningful.
>
> In other words, it should not be done.
>
> There is a lot wrong with re-sampling, gridding, within DEMs, with merging
> grids,
> reprojecting and interpolation surfaces. And GIS techs are pretty guilty
> of that,
> so are their supervisors.
> The tools we provide should point that out clearly and not allow for it.
>
> Key to those questions remain 'ethics', metadata of course (!) and then
> always a comparison as a benchmark for
> accuracy and to see the actual gain of such re-samplings.
>
> (but let's agree that TINs are only one way of getting a surface, often
> not the best one,
> when compared to the 'truth'. Playing around with them for best output is
> not a bad idea)
>
>   Very best
>     Falk Huettmann
>
>
>
>
> On Fri, Oct 4, 2019 at 4:00 AM Nicolas Cadieux <
> nicolas.cadieux at archeotec.ca> wrote:
>
>> Hi,
>>
>> You cannot invent new data between point without doing an interpolation.
>> Your choice of interpolation will determine the quality of this data.  The
>> only way I can think of is to create a raster from this TIN.  Then,
>> resample (re-interpolated) this raster with a finer pixel and then make a
>> new TIN.  This may create a finer TIN but this will significantly alter the
>> original data.  You would need to evaluate the results and keep a backup of
>> the old files.
>>
>> Alternative, I would try with Mesh Lab.  It’s open source and probably
>> has Mesh densification methods that would be more adapted.  Cloud Compare
>> also has interesting algorithms.
>> Nicolas
>>
>> > Le 4 oct. 2019 à 03:40, joolek <joolek.o at gmail.com> a écrit :
>> >
>> > Hi Experts,
>> >
>> > I've tried so many software's without success.
>> > Is it possible to upsample existing TIN? What I mean is for example
>> divide each triangle into two for example. Not interpolation but somehow...
>> subdivide or add more vertices between existing one?
>> > Thank you for all your time
>> > J
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-- 
Saber Razmjooei
www.lutraconsulting.co.uk
+44 (0)7568 129733
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