________________________________________ edgar.soldin wrote: On 14.12.2014 21:13, Rahkonen Jukka (Tike) wrote: > Hi, > > 1) In WMS is is only compulsory to advertize WGS84 bounding box -> as long as > OpenJUMP is missing CRS support zoom to bounds will not work generally. > However, additional BBOX:es do exist often and zoom to layer is possible to > perform. >> 2) As Michaël wrote, automatic zoom to bounds should not be done if project >> already has layers - vector, raster or other WMS layers
> just out of interest. why? just noticed we also do not do it for a second > dataset opened. wouldn't a user > expect to see what he just opened? If you are digitizing something like a lamp posts in Hamburg and you add some background imagery from nation wide WMS service you probably do not want automatic zoom to whole country. >> 3) Bounding boxes which are advertised by the WMS server may be wrong. > wouldn't the wms image placed wrongly then as well? or are there bboxes > separate from the image georeference? Yes, the bounding boxes of the GetCapabilities are only metadata which tell the maximum extents of the layer. On our server I tend to set the same bounding box that covers whole Finland for all the layers. When a map is requested from WMS service the request contains exact BBOX "please send me an image to fill this box". >> 4) Zoom to extents of the WMS layer does not necessarily show any map >> because the layer may have more strict scale range. > how would one find out these scale ranges? especially in a client like OJ. >From GetCapabilities. The name of the element depends on the WMS version, in >WMS 1.3.0 they are MinScaleDenominator/MaxScaleDenominator. However, those are >not mandatory elements. You can find an example from http://demo.opengeo.org/geoserver/wms?service=WMS&request=GetCapabilities&version=1.3.0. There you can also see a long list of supported projection and that BoundingBoxes are missing for most of them. >> >> I would say that [2] should be taken into account when implementing and the >> most robust zoom to layer should be based on re-projected WGS84 BBOX [1]. > because WGS84 BBOX is the most reliable? Because it is the one that for sure exists. Of course you could check the BBOX of the requested projection and if it is not found, WGS84 BBOX. Or withour CRS support just try if the BBOX of requested projections exists and if not, just forget it. >> [3] and [4] are mainly something that users should be aware, though WMS >> GetCapabilities may contain some info about the valid scale range. > is this usually interpreted by client software and given to the user? Usually not. QGIS does interpret scale hints and build "Zoom to best scale" according to those if I remember right. >>As a helper feature for recognizing the wrong BBOXes there could be a >>function that converts the BBOXes from the server GetCapabilities into >>vector polygons. > is that an idea to address my former question? still leaves, how other > softwares address it, do they at all? I have never seem a client that tries to draw the bounding boxes. However, I can imagine two good use cases: A WMS server manager like me could fast check if that part of GetCapabilities looks good and server is well configured. For example we have services with tens of layers and some misconfugured BoundingBox would be hard to notice. Another use case is the end user of WMS server that serves many layers with different bounding boxes. For example the server that Andrei Nacu is using is hosting some world wide layers but also some which cover only Bucharest. -Jukka- > ..thanks ede ------------------------------------------------------------------------------ Download BIRT iHub F-Type - The Free Enterprise-Grade BIRT Server from Actuate! Instantly Supercharge Your Business Reports and Dashboards with Interactivity, Sharing, Native Excel Exports, App Integration & more Get technology previously reserved for billion-dollar corporations, FREE http://pubads.g.doubleclick.net/gampad/clk?id=164703151&iu=/4140/ostg.clktrk _______________________________________________ Jump-pilot-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel ------------------------------------------------------------------------------ Download BIRT iHub F-Type - The Free Enterprise-Grade BIRT Server from Actuate! Instantly Supercharge Your Business Reports and Dashboards with Interactivity, Sharing, Native Excel Exports, App Integration & more Get technology previously reserved for billion-dollar corporations, FREE http://pubads.g.doubleclick.net/gampad/clk?id=164703151&iu=/4140/ostg.clktrk _______________________________________________ Jump-pilot-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
