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I am hoping to get help with what I need to do in order to allow a user on my OpenLayers map to download a portion of a GeoTiff they are viewing through a WMS. The data is hosted through GeoServer. I would like the user to be able to simply click a button and download the bounds of the original file

I am not sure what steps I need to take in order to begin this process. I have worked a lot with serving geospatial data. But never in a way which allows the user to download the data. Any guide in the right direction would be great. Thanks!

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up vote 5 down vote accepted

i think you should use WCS instead of WMS for sharing raster datasets on the Web. AFAIK, wms dont have this capabilities for sharing tiff images.

From Wikipedia:

Unlike OGC Web Map Service (WMS), which portrays spatial data to return static maps (rendered as pictures by the server), the Web Coverage Service provides available data together with their detailed descriptions; defines a rich syntax for requests against these data; and returns data with its original semantics (instead of pictures) which may be interpreted, extrapolated, etc., and not just portrayed.

Unlike OGC Web Feature Service (WFS), which returns discrete geospatial features, the Web Coverage Service returns coverages representing space/time-varying phenomena that relate a spatio-temporal domain to a (possibly multidimensional) range of properties. As such, WCS focuses on coverages as a specialized class of features and, correspondingly, defines streamlined functionality.

and you can check out WCS info for geoserver here.

Benefits of WCS

WCS provides a standard interface for how to request the raster source of a geospatial image. While a WMS can return an image it is generally only useful as an image.The results of a WCS can be used for complex modeling and analysis, as it often contains more information. It also allows more complex querying - clients can extract just the portion of the coverage that they need.

WCS output formats

Georeferenced formats:

    GeoTiff - (format=geotiff)
    GTopo30 - (format=gtopo30)
    ArcGrid - (format=ArcGrid)
    GZipped ArcGrid - (format=ArcGrid-GZIP)

i hope it helps you..

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Thanks! That def is what I need. Haven't worked with WCS before - its just been one of those that I am used to skipping over. –  KyleK Nov 15 '12 at 14:20
    
Word of warning about WCS - not many people use it and support for it is lacking. When I used it a few years ago, even the "reference standard" had quite a few glaring bugs (hopefully since fixed). Its also massively processor intensive depending on what you're doing compared to WMS/WFS. –  GIS-Jonathan Nov 15 '12 at 14:26
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