Thanx Martin
it sounds promising.. can we somehow give any help at this conceptual stage?


Von: postgis-users <[email protected]> Im Auftrag von 
Martin Davis
Gesendet: Mittwoch, 3. Juli 2019 16:54
An: PostGIS Users Discussion <[email protected]>
Betreff: Re: [postgis-users] PostGIS new geometry type with defined precision?

JTS already provided a mechanism to specify a precision for geometry, and this 
is respected by a number of operations as well (notably the overlay operations 
intersection et al and buffer - but not the spatial predicates, yet).  GEOS 
should provide this as well, or is close to doing so.  And I'm currently 
working on a new implementation of overlay to improve robustness, which will 
improve fixed precision computation as well.

The issue of handling fixed precision for predicates is a good question.  I 
have an algorithm in the conceptual stages for this.  But it may be difficult 
to make it consistent with the overlay operations on a performant way.  I 
intend to write up a survey of the options soon.

My current thinking is that precision will be specified as a parameter to 
geometry operations.  No new type will be required. It might be nice to have 
precision specified in column metadata somehow, but not sure how this could work

On Wed, Jul 3, 2019, 5:48 AM Darafei "Komяpa" Praliaskouski 
<[email protected]<mailto:[email protected]>> wrote:
Hi,

Can you describe how the operations like Intersection should behave in such 
type? E.g. if you have a type with 0 decimals (say), and have a line going from 
(0,0) to (1,1) intersect with a line going from (1, 0) to (0, 1) - what is the 
intersection point that is going to be reported? Will that ST_Intersection in 
turn ST_Intersects=true with original point?

There are a number of such requests across the years but nobody seems to 
propose a working algebra for such type, and without it it's not going to get 
implemented.

On Wed, Jul 3, 2019 at 2:43 PM Giunta Igor 
<[email protected]<mailto:[email protected]>> wrote:
How can a precision be assigned to a geometry, e.g. a point/line/polygon to 3 
decimals, in order that any input/output will be given in that precision 
(without usage of rounding functions like snap2grid)
How can the problem be tackeld? Shall we request to include new types? Or shall 
we rather let develop a new feature?

I guess we are not the first users facing this problem.


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Darafei Praliaskouski
Support me: http://patreon.com/komzpa
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