Question
Specifying WMS pixel size
Can I specify the pixel size when requesting an image from a WMS service? I'm using a Search evelope in the WMS reader then writing to a tiff file. The image I end up with has 14m pixels, but I would like 0.5m pixels, which is the full resolution of the Aerial Photography.
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Hi,
that would depend on your WMS service implementation. According to the WMS standard (version 1.1.1), you specify a bouding box with an SRS and the height and width (in pixels) of the image you want to retrieve. It is then up to the WMS server to decide which layers and how to style the requested image. The relationship between pixels and ground units is inferred indirectly from these parameters, depending on the setup of your WMS style sheets.
The easiest way to test is to copy the URL sent to the WMS server from the FME log and paste it into the address bar of your favorite browser. You can then play around with the parameters BBOX, HEIGHT and WIDTH to see what is possible. Be aware that certain combinations of these values might give a stretched result, which might not be what you want.
The standards are described here (http://www.opengeospatial.org/standards/wms), if you need further details.
David
Thanks. I will have to figure out some way then to calculate the right height and width values based on the min max xy coordinates of a rectangle that the user will draw on a webmap. Was hoping FME had already built something to do that for me.