Drawing Raster Query Results

[Steve Lime]

Result sets can span many layers and data types so it can get messy very quickly.

Steve

>>> On 4/23/2007 at 4:48 PM, in message
<f3b73b7d0704231448j82fd0fwd93ad441737ec146 at mail.gmail.com>, Tamas Szekeres
<szekerest at GMAIL.COM> wrote:
> Frank,
> 
> I'm personally not too pleased with the current resultcache approach
> as the primary solution of storing a results of a query. Why don't we
> add the results to a predefinied inline layer? This approach would
> provide all of the facilities for styling the results as we have
> normally for a layer. The user could additionally swich on/off this
> layer or eventally start a subsequent query based on this previous
> query in another layer for example.
> Threating the raster layers as point layers is a bit quicky for me.
> 
> Best regards,
> 
> Tamas
> 
> 
> 2007/4/23, Frank Warmerdam <warmerdam at pobox.com>:
>> Folks,
>>
>> A couple years ago I implemented support for "query" against a raster layer.
>> Such queries essentially return a list of point features, generally one for
>> each pixel that satisfies the query criteria.
>>
>> Recently a user has run into problems when they try to draw a map of the
>> query result.  This isn't something I've ever tried before, and to be 
> honest,
>> I'm a bit vague on how queries are normally used in MapServer.  I assumed 
> they
>> were mostly used for populating tabular results which does work fine.
>>
>> The drawing a query layer for a map result doesn't work properly, as 
> documented
>> in:
>>
>>    http://trac.osgeo.org/mapserver/ticket/2069 
>>
>> The question, to my mind, is whether it makes sense to try and draw point
>> features from a raster query result on a map, and if we did so how do we
>> differentiate styling used for the raster from styling used for the query
>> results which are a very different sort of data.
>>
>> I'm tempted to modify msDrawQueryLayer() to do nothing raster layers, but to
>> issue a debug message indicating that the layer is being skipped since 
> drawing
>> raster query results is considered an unclear request.
>>
>> If anyone has an opinion contrary to my idea to disallow this, please let me
>> know on this list, or via the ticket.
>>
>> Best regards,
>> --
>> ---------------------------------------+--------------------------------------
>> I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com 
>> light and sound - activate the windows | http://pobox.com/~warmerdam 
>> and watch the world go round - Rush    | President OSGeo, http://osgeo.org 
>>