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#1 2007-10-25 20:48:09

Margaret788
Member
Registered: 2007-07-30
Posts: 3

Using scales

Hi there

I've found the list of scales for 18 levels of zoom but am not sure how to use them. 

Is there any way of finding what zoom level you are at at any time without just counting?  In any case, on counting, I seem to find 19 levels of zoom, or does the first one, a strip of multiple worlds, count as 0?

I'm OK with using the respresentative fractions given but does this not depend on the resolution you are using at the time?  Is there a 'standard' size of window for which these scales are correct?

Thanks in advance for any explanations.

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#2 2007-10-26 09:37:54

Lambertus
Administrator
From: Apeldoorn (NL)
Registered: 2007-03-17
Posts: 3,269
Website

Re: Using scales

The number of zoomlevels and zoomfactors can differ with every map. The higher zoomlevels impose an exponential growth in tiles and harddisk space needed. So every website can decide to provide tiles for only a certain amount of zoomlevels. A zoomlevel shows the same data on both a low resolution or a high resolution screen. Most (if not all) maps based on OpenStreetMap data are using OpenLayers as the map software. I suggest you'd take a look over there for the definitions of zoomlevels.

If you view the map on http://www.openstreetmap.org the zoomfactor can be found if you look at the 'permalink' link on the bottom-right side of the map. The map on http://informationfreeway.org shows a ruler.


Mapping tools: Garmin GPSmap 60CSx, Giant Terrago 2002

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