Opened 6 years ago

Closed 6 years ago

Last modified 6 years ago

#2032 closed enhancement (invalid)

Higher dimension support for ST_ClosestPoint

Reported by: strk Owned by: pramsey
Priority: medium Milestone: PostGIS 2.1.0
Component: postgis Version: 2.0.x
Keywords: Cc:

Description

When you look for "the closest point" I think you want a point with all dimensions in it. At least Z, if the first geometry had one.

What's the closest point to 'POINT(6 0)' on 'LINESTRING(0 0 0, 10 0 40)' ?

I think it should be 'POINT(5 20)', and not 'POINT(5 0)'

Change History (3)

comment:1 Changed 6 years ago by nicklas

I'm still around :-)

First, I guess you mean that today's function returns 'POINT(6 0)' and not 'POINT(5 0)'.

Then I think that you suggest the answer 'POINT(5 0 20)' and not 'POINT(5 20)', right?

I disagree. ST_ClosestPoint is a 2d function. When I implemented ST_3dClosestPOint we had (Regina and me I think) a discussion about if we couldn't include the 3d-functionality in the ST_ClosestPoint function. The reason we didn't is that you should be aware about what dimensions is used in the calculation. You can work on data sets where you are not aware of the z-value. And then you will just get very strange 2d-results. If you want the z-value in the calculation you should use ST_3DClosestPoint. But I see htt ST_3DClosestPoint is handling this situation in a strange way. I will open a ticket on that.

comment:2 Changed 6 years ago by robe

Resolution: invalid
Status: newclosed

comment:3 Changed 6 years ago by strk

For reference the ticket about weird result by ST_3DClosestPoint is #2034

But I'd note that ST_Intersection() returns 3dZ if any input is 3dZ...

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