[raster]: Clarify meaning of neighborhood width/height (distance in 2.1)

[robe]

I guess I don't use the neighborhood map algebra functions much. Leo asked what our convention is for neighborhood width/height (distance)

is it distance from reference cell or the total width/height that includes the center cell (which would seem to make it always odd)

I realized I embarassingly don't know the answer and just assumed it was radius (distance from center). Our docs don't help much. They are ambiguous.

I always assumed we measured as distance from reference cell so

2,2 —> means a matrix of 5x5 11011 (where 0 is the center cell)

but other stuff I've read seems to contradict that assumption and define it as the total width/height (5x5)

[Bborie Park]

The convention is the number of pixels from the reference cell.

So, specifying ngbwidth = 1 and ngbheight = 2 of ST_MapAlgebraFctNgb() would mean a 3 x 5 neighborhood.

1 1 1
1 1 1
1 0 1
1 1 1
1 1 1

Is this for 2.1 or 2.0? The title seems to indicate 2.1 while the milestone is set for 2.0.4

[robe]

I was meaning both. It was unclear for me in both docs. By convention we mark it for the earliest version we plan to change.

Distance seems a clearer concept — but distancex,distancey is absolutely equivalent to ngbwidth, ngbheight (of 2.0) which is what I wanted to clarify. So my assumption is correct on both counts?

[robe]

fixed for 2.1.0 at r11177

[Bborie Park]

Yes. Your assumption is correct.

[robe]

clarified for 2.0 at r11178