[Mobilitydb-users] Query regarding intersection of a temporal point with Z dimension and polygon

[Sharath S Bhargav]

Hello Esteban,

The method st_3DIntersection is required for true 3D intersection. While
st_intersection does return results with points having 3 dimensions by
averaging the Z dimension value. But the results returned from MobilityDB
seem to indicate that is also not supported since I get a tbool with only
false values. Can I assume that MobilityDB does not support 3 dimensions in
any of the intersection functions even in a 2.5D fashion?
If the tintersect function could return true by just considering the 2
dimensions of the trajectory and average out the Z dimension that would
also work for me. I expected this behaviour since MobilityDB delegates the
spatial calculations to PostGIS and PostGIS does actually do the same and
return the intersecting line string as shown in the query example. So
considering PostGIS response, I was hoping MobilityDB could return a true
period set. It would be great if you could kindly clarify the behaviour in
this scenario. Apologies if I seem to be asking trivial questions, I am new
to the Spatio-Temporal Databases.

On Sat, Mar 13, 2021 at 3:14 AM Esteban Zimanyi <estebanzimanyi at gmail.com>
wrote:

> Dear Sharath
>
> As I mentioned before, MobilityDB delegates to PostGIS the calculation of
> the spatial operations. According to what you described, to implement your
> scenario you require to use the PostGIS method ST_3DIntersection
> https://postgis.net/docs/ST_3DIntersection.html
> It is stated in the above link that this method needs SFCGAL backend.
>
> We have never used MobilityDB together with SFCGAL. We could envision
> starting this exploration in the future, but currently we have many other
> things in the development pipeline of MobilityDB.
>
> If you want to start this exploration, we could provide you guidance in
> this regard and depending on our availability, we can also extend
> MobilityDB to make this happen.
>
> Esteban
>
>

-- 
Regards,
Sharath
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