Re: MySQL GIS


colinr23@xxxxxxxxx wrote:
> as long as all your data is stored in the same units, distance
> calculations should be correct. If you have datasets in different
> projections, you'll have to convert them prior to doin calculations,
> maybe with a custom written function. The actual nuts and bolts for
> the calculations should be easy enough to find. I'd convert all my
> data in arc then load it into mysql once its all in the same projection.

I don't know too much about projections actually...

I'm guessing putting the data in the same projection guarantees that
each unit will be equidistant, so that the distance measurements will
work properly on a plane. Is that right?

One more thing, if that is true, then I'm guessing a projection can't
work, for example, for the whole world, they would have to be confined
to a limited space. Otherwise, how would the units be equidistant?

Maybe I'm being naive about this, but can PostGIS make proper distance
calculations w/just lat/lon? Or does it have to be using some other
projection?

.

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