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From "patrick o'leary" <pj...@pjaol.com>
Subject Re: [spatial] Cartesian "Tiers" nomenclature
Date Wed, 30 Dec 2009 00:54:06 GMT
Marvin, then by all means write your own sir



On Tue, Dec 29, 2009 at 4:13 PM, Marvin Humphrey <marvin@rectangular.com>wrote:

> On Tue, Dec 29, 2009 at 03:55:22PM -0800, Marvin Humphrey wrote:
>
> > I'll save conclusion #2 for a separate email.
>
> Conclusion # 2
> ==============
>
> The concepts used in spatial contrib are easy -- much easier than I'd come
> to
> assume, given how drawn out this conversation has gotten.  (Projections are
> hard, but I already grok them, and they play a minor role.)  In fact,
> spatial
> contrib works almost exactly like I would have expected.  Some places I've
> worked have implemented almost exactly the same algorithms independently.
>
> I continue to disagree with Patrick about elevating the word "tier".  There
> doesn't seem to be anything special about it.  In fact, the "tiers" in
> spatial
> contrib refer to zoom levels which are always powers of two...
>
>    tier 0: 1x1 =  1 tile
>    tier 1: 2x2 =  4 tiles
>    tier 2: 4x4 = 16 tiles
>    ...
>
> ... but for this algorithm, different rasterization resolutions need not
> proceed by powers-of-two.  IMO CartesianGrid is better, as it encapsulates
> the
> same data using more popular terminology.  You could also say that a
> CartesianGrid has a resolution zoom level, and that in this implementation
> it's tied to a power-of-two "tier".  However, assigning such a meaning to
> the
> word "tier" is arbitrary.
>
> I might even suggest ZoomLevel as an alternative to CartesianTier, and
> bounce
> the term "Rasterization" out there for kicks.
>
> On the other hand, "Cartesian Tile" would not be appropriate at all as a
> substitute for "Cartesian Tier".  My sense is that "tile", "box", and
> "cell"
> are all basically the same and refer to a single rectangle, while
> Tier/Grid/ZoomLevel/etc. are composites encapsulating multiple
> tiles/boxes/cells.
>
> Marvin Humphrey
>
>

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