[postgis-users] electronic GIS data scale
thy at 42.dk
Tue Jan 6 13:48:00 PST 2009
On Tue, Jan 06, pcreso at pcreso.com wrote:
> I disagree that it is not pertinent to use scale with vector data. I
> think it can be quite relevant:
> Much vector data has been digitised from hard copy. Hard copy always
> has a scale, which it is useful to record with the digitised data.
Agreed, but this is provenance metadata. It is not a scale for the
vector data in any meaningful sense.
> Also, Postgis is frequently used as a data server for web mapping
> applications. These use zoom/scale layers, and different datasets are
> enabled at different scales. Managing this information in the database
> is very helpful for data driven applications, which can use this
> information to generate different outputs depending on the view scale.
Again agreed, but this scale is in metres per pixel, whereas the scale
when digitizing is unitless. So you'd also do well to save the unit of
... et nemo ex vobis interrogat me: »Quo vadis?«
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