## jump-pilot-devel

 [JPP-Devel] WMS and Min/Max scale From: Paul Austin - 2007-12-10 19:18:19 ```Does anyone know the formulas to convert between the ScaleHint in a WMS request and the corresponding min/Max scale on a WMS layer? Cheers, Paul ```
 Re: [JPP-Devel] WMS and Min/Max scale From: Rahkonen Jukka - 2007-12-11 10:00:17 ```Hi, I suppose you have read the OGC specification: "Layers may include a element that suggests minimum and = maximum scales for which it is appropriate to display this layer. Because WMS output is = destined for output devices of arbitrary size and resolution, the usual definition of = scale as the ratio of map size to real-world size is not appropriate here. The following = definition of Scale Hint is recommended. Consider a hypothetical map with a given Bounding = Box, width and height. The central pixel of that map (or the pixel just to the = northwest of center) will have some size, which can be expressed as the ground distance in meters = of the southwest to northeast diagonal of that pixel. The two values in ScaleHint are the = minimum and maximum recommended values of that diagonal. It is recognized that this = definition is not geodetically precise, but at the same time the hope is that by = including it conventions will develop that can be later specified more clearly." What scale are you interested in? ScaleHint gives approximately the = real world size of a pixel, and I guess that for converting it to = traditional map scale you need to know the pixel density of the media = used for presenting the image (screen, paper).=20 -Jukka Rahkonen- > Puolesta Paul Austin > L=E4hetetty: 10. joulukuuta 2007 21:17 > Vastaanottaja: JUMP Developer > Aihe: [JPP-Devel] WMS and Min/Max scale >=20 > Does anyone know the formulas to convert between the=20 > ScaleHint in a WMS request and the corresponding min/Max=20 > scale on a WMS layer? >=20 > Cheers, > Paul >=20 > -------------------------------------------------------------- > ----------- > SF.Net email is sponsored by:=20 > Check out the new SourceForge.net Marketplace. > It's the best place to buy or sell services for just about=20 > anything Open Source. > http://sourceforge.net/services/buy/index.php > _______________________________________________ > Jump-pilot-devel mailing list > Jump-pilot-devel@... > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel >=20 ```
 Re: [JPP-Devel] WMS and Min/Max scale From: Andreas Schmitz - 2007-12-11 10:05:11 Attachments: application/pgp-signature ```Rahkonen Jukka wrote: Hi, > "Layers may include a element that suggests minimum and maximum scales > for which it is appropriate to display this layer. Because WMS output is destined for > output devices of arbitrary size and resolution, the usual definition of scale as the ratio of > map size to real-world size is not appropriate here. The following definition of Scale > Hint is recommended. Consider a hypothetical map with a given Bounding Box, width > and height. The central pixel of that map (or the pixel just to the northwest of center) will > have some size, which can be expressed as the ground distance in meters of the southwest > to northeast diagonal of that pixel. The two values in ScaleHint are the minimum and > maximum recommended values of that diagonal. It is recognized that this definition is > not geodetically precise, but at the same time the hope is that by including it conventions > will develop that can be later specified more clearly." > > What scale are you interested in? ScaleHint gives approximately the real world size of a pixel, and I guess that for converting it to traditional map scale you need to know the pixel density of the media used for presenting the image (screen, paper). The WMS 1.3.0 specification may also give hints, since they changed the meaning of the ScaleHints (and renamed it to Min/MaxScaleDenominator. See Chapter 7.2.4.6.9 Scale denominators. Best regards, Andreas -- l a t / l o n GmbH Aennchenstrasse 19 53177 Bonn, Germany phone ++49 +228 18496-11 fax ++49 +228 1849629 http://www.lat-lon.de http://www.deegree.org ```