[postgis-users] A table of DE-9IE patterns and types of topological relations

[Martin Davis]

Good to hear.  I did run it through an online color accessibility checker,
so I guess that has worked out.

On Mon, Apr 18, 2022 at 7:20 PM Jim Klassen <klassen.js at gmail.com> wrote:

> It looks a lot better to me.
>
> On 4/18/22 16:52, Martin Davis wrote:
>
> Is this any better?
>
> https://postgis.net/docs/manual-dev/using_postgis_query.html#DE-9IM
>
> On Mon, Apr 18, 2022 at 2:31 PM Jim Klassen <klassen.js at gmail.com> wrote:
>
>> As an aside, I am noticing these graphics probably aren't very accessible
>> to people with vision impairments.  There is a lack of meaningful alt-text,
>> a general fuzziness/soft edges, and use of several colors of similar
>> lightness.  In particular, the red is hard to separate out in grayscale and
>> the red is the part that is most important as it is describing the part of
>> the image that applies to that grid cell.
>>
>> I'm not sure if it will come through on the list, but I've converted the
>> 3x3 grid image from [1] to grayscale below as an example.  I know I'd have
>> a very hard time picking out which section was what if I didn't already
>> know the answer ahead of time.
>>
>>
>>
>> [1] https://postgis.net/workshops/postgis-intro/_images/de9im3.jpg
>>
>> On 4/15/22 15:08, Shaozhong SHI wrote:
>>
>> This is very interesting.
>>
>> However, this needs to be further detailed with a table to explain a
>> variety of cases and uses.
>>
>> Regards,
>>
>> David
>>
>> On Fri, 15 Apr 2022 at 02:48, Paul Ramsey <pramsey at cleverelephant.ca>
>> wrote:
>>
>>> https://postgis.net/workshops/postgis-intro/de9im.html
>>>
>>> > On Apr 14, 2022, at 4:35 PM, Shaozhong SHI <shishaozhong at gmail.com>
>>> wrote:
>>> >
>>> > The use of ST_Relate appears very attractive.  However, there appears
>>> not yet a table detailing DE_9IE patterns and types of topological
>>> relations.
>>> >
>>> > There also appears that not much literature on the use of it for data
>>> quality assurance or things like deriving quality data from raw data.
>>> >
>>> > Can anyone enlighten me?
>>> >
>>> > Regards,
>>> >
>>> > David
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