[postgis-users] PostGIS new geometry type with defined precision?

[Giunta Igor]

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


Von: postgis-users <postgis-users-bounces at lists.osgeo.org> Im Auftrag von Martin Davis
Gesendet: Mittwoch, 3. Juli 2019 16:54
An: PostGIS Users Discussion <postgis-users at lists.osgeo.org>
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 <me at komzpa.net<mailto:me at komzpa.net>> 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 <Igor.Giunta at tg.ch<mailto:Igor.Giunta at tg.ch>> 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
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