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

[Martin Davis]

Yes, the plan is to port the new overlay code to GEOS, and then expose it
in PostGIS.  The function design suggested in Dan's previous work seems
reasonable, so the new PostGIS overlay functions will probably look like
that.

I'm making good progress on the code.  Still hoping for an early fall
arrival in GEOS and PostGIS.


On Mon, Jul 15, 2019 at 12:21 AM Giunta Igor <Igor.Giunta at tg.ch> wrote:

> Hi Martin
>
> I just found some exchanges here:
>
>
> http://osgeo-org.1560.x6.nabble.com/Fixed-precision-for-ST-Intersection-ST-Union-etc-td5255487.html
>
>
>
> In the meanwhile GEOS3.6 has been sent out with
> GEOSGeom_{set,get}Precision according to
>
> http://osgeo-org.1560.x6.nabble.com/GEOS-3-6-0-released-td5292606.html
>
>
>
> On the PostGIS side I don't find any correspndance.
>
> Is your work going to integrate this GEOS functions into PosGIS or your
> approach is independent?
>
>
>
>
>
>
>
> *Von:* postgis-users <postgis-users-bounces at lists.osgeo.org> *Im Auftrag
> von *Martin Davis
> *Gesendet:* Mittwoch, 3. Juli 2019 18:02
> *An:* PostGIS Users Discussion <postgis-users at lists.osgeo.org>
> *Betreff:* Re: [postgis-users] PostGIS new geometry type with defined
> precision?
>
>
>
> 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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