I believe the 3rd dimension is sometimes used as time (instead of elevation).
Example:
> 5.19. Trajectory Functions Abstract
> These functions support working with trajectories. A trajectory is a linear
> geometry with a measure (M value) on each coordinate. The measure values must
> increase along the line. Spatio-temporal data can be modelled by using
> relative times (such as the epoch) as the measure values.
https://postgis.net/docs/manual-3.1/reference.html
You might be able to use QGIS to help visualize this, though I haven't used it
with 3d data, so I can't provide any more concrete guidance on that front.
Jim
On May 23, 2022 2:17:28 AM EDT, Rory Meyer <rory.me...@vliz.be> wrote:
>Afternoon everyone,
>
>I'm assisting a PhD student with their work and I think PostGIS could provide
>some interesting tools. The problem is that it's using spatial data in a non
>GIS way.
>
>The student is monitoring the settling behaviour of oyster sprats (larvae) to
>determine the natural features that lead up to oyster reefs. The experiment is
>to have a bunch of sprats in a petri dish, simulate a predator or existing
>oyster reef using chemicals, and to measure the settlement behaviour over
>several hours using a webcam mounted above the petri-dish. The initial steps
>would be to use computer vision tools to get an (x,y,t) vector for each oyster
>sprat, or movement segment, for the duration of the experiment. Using PostGIS
>functions to build trajectories, calculate average/min/max speed per segment,
>see if there are any intersections between multiple sprats, possibly map
>trajectories to behaviours. I'm not sure what else, I'm not a biologist.
>
>My question is how do you do this with a non-spatial SRID? Can I just use
>pixel locations as X,Y fields, set the SRID to 0 and get pixels/sec out of any
>ST_funcs? Is there some previous work done on creating a camera specific SRID
>(probably a bit overkill) to take into account distortions and transform
>pixel/sec to meter/sec?
>
>Regards,
>Rory
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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