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

[Martin Davis]

We're still at least a month out from having PostGIS code to release, but
once it's out feedback will be appreciated.

On Wed, Jul 3, 2019, 8:21 AM Giunta Igor <Igor.Giunta at tg.ch> wrote:

> 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>
> 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> 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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