[geos-devel] WKT Precision

Andrew Hershberger andrew.d.hershberger at gmail.com
Tue Jan 5 18:55:13 PST 2021


I exposed these features in GEOSwift earlier last year, and I do remember
finding the behavior a bit confusing. Here are some links to the community
request that led me to expose it and the resulting change:

https://github.com/GEOSwift/GEOSwift/issues/196
https://github.com/GEOSwift/GEOSwift/pull/197


On Tue, Jan 5, 2021 at 6:39 PM Martin Davis <mtnclimb at gmail.com> wrote:

> And for the record, I am -10 on outputting scientific notation, except for
> extremely large numbers (say > 10^20 - which should rarely occur in real
> data).  It just makes the output hard to read.
>
> On Tue, Jan 5, 2021 at 4:35 PM Martin Davis <mtnclimb at gmail.com> wrote:
>
>>  setTrim and setRoundingPrecision are GEOS-specific (not in JTS).
>>
>> What JTS has is WKTWriter.setPrecisionModel().  What that does is to set
>> the max number of decimal places according to the precision supplied (e.g.
>> scale = 10 produces 1 decimal, scale = 100 produces 2, etc)
>>
>> I like the simplicity of having setRoundingPrecision always apply to the
>> decimal places.  I can't really envision a scenario where there is any
>> point in reducing the sig figs (i.e. lopping off digits to the L of the
>> decimal place) since they would have to be output as zeroes anyway, so
>> there is no savings.
>>
>> And I would think having trim = true as the default would be most
>> friendly, since there doesn't seem to be any value in keeping trailing
>> zeroes after the decimal point.
>>
>> On Tue, Jan 5, 2021 at 3:41 PM Paul Ramsey <pramsey at cleverelephant.ca>
>> wrote:
>>
>>> What do people think is the best practice for outputing WKT precision?
>>
>>
>> (Also, what do these knobs (setTrim, setRoundingPrecision) mean in JTS
>>> world? I'm guessing our behaviour is *not* an exact analogue.
>>>
>>
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