[GRASS-user] meaning of "geometry"

[Dave Roberts]

Thanks Rich.  Comments interspersed.

On 10/25/16 13:33, Rich Shepard wrote:
> On Tue, 25 Oct 2016, Dave Roberts wrote:
>
>> So now when I see "geometry" in a manual page or GRASS-user posting I
>> interpret that to mean "vertices, nodes, centroids, and associated
>> categories ordered by the (not necessarily consecutive) layer numbers" as
>> that's the essential nature of a record in the coor file that manages all
>> this.
>
>> Obviously that's more operational than conceptual so I was wondering
>> where the concept of geometry is actually defined.
>
> Dave,
>
>   If I may contribute a thought or two to this thread: there are two
> definitions of 'geometry' which we all use. One definition is coordinate
> geometry which can be described as where points on a geographic surface are
> located; the x, y values.
>

Right, this is what most of us think of immediately.

>   Then there's object geometry. When setting a dinner table it's common to
> place plates, glasses, and flatware in designated positions relative to
> each
> other. Same with the controls in a vehicle: the accelerator is on the
> right,
> the brake in the center and the clutch on the left (at least here in the
> US; it's been decades since I drove in the UK).
>
>   If we think of GRASS' geometry as object geometry, the placement of
> vector
> objects relative to each other it might lessen any confusion.
>

But here again is the confusion.  The position of objects relative to 
each other is independent of the number of layers associated with each 
object.  And so it seems to me that when GRASS users talk about 
"geometry" they mean space AND layers combined because they are 
inseparable in the implementation.  Perhaps we need a new word for 
spatial realization and attributes combined rather than geometry.

Thanks, Dave