mapsize

Rob Atkinson rob at socialchange.net.au
Fri Mar 17 19:12:40 EST 2000


FYI

The current behaviour, which is to create the smallest possible extent
that includes, and is centred on,  the requested extent and conforms to
the aspect ratio of the image, is as specified in the OpenGIS Consortium
Web Map Server specification.

A perl wrapper for mapserv to conform to the OGC specification is under
construction. We'll be putting it up on  public CVS site as soon as we
can.

Steve, I have asked this before - is it possible, and can you provide an
example, of specifying the projection to be used from the CGI
parameters?

Future plans include actually parsing the .map file to create the
"Capabilities Document" in XML required for OGC conformance. (Its
currently hand built)

Also, a modified version of the mapimage Applet that uses the OGC
protocol to get a base map and allows Javascript control of the extent
to fetch will be posted. Just need to check the copyright on the
original code to see if this is OK.

The community will be free to take these and modify them further.

Regards

Rob Atkinson

Frank Lochter wrote:

>  Hi Steve,
> I have a small problem and would like to discuss this here.
>
> 1. When I specify a bbox (lat, lon), then the result map should  fit
> exactly within this BBox.
> 2. When I specify a width and height, the result bitmap should have
> this width and height.
> 3. What is when I specify bbox and width and height? Then something is
> over defined!
>     - I assume, the result should exactly fit in the bbox AND the
> bitmap should fit exactly in one
>       dimension width or height and the other dimension of the bitmap
> should be calculated
>       on the fly!
> - I get something unexpected when the map server extracts the bbox,
> especially when I
> like to integrate the bitmap into an other application and assume,
> that the bitmap has the
> bbox, that I used to generate it.
>
> Is there any way to get what I assume in 3. !
>
> Sincerely
>
> Frank Lochter
>
> Stephen Lime wrote:
>
>> Yup, the extent is recaclulated based on the shape of the extent and
>> the window
>> size/shape. You are gauranteed to see the whole extent plus a bit
>> more. The
>> algorithm fits your requested extent in either x or y dimension
>> (whichever fits
>> best) and then pads the other dimension as needed. This has to be
>> done in
>> order to get the right map to image transformation. You wouldn't
>> necessarily
>> have to actually display data outside the actual requested extent
>> but that would
>> result in a great deal of blank space in the resulting image, so the
>> computed extent
>> is used to select/clip data.
>>
>> Steve
>>
>> Stephen Lime
>> Internet Applications Analyst
>>
>> Minnesota DNR
>> 500 Lafayette Road
>> St. Paul, MN 55155
>> 651-297-2937
>>
>> >>> Ralf Puchert <puchert at gfz-potsdam.de> 03/16/00 10:33AM >>>
>> Hello,
>>
>> When we use
>>
>> http://130.
>> 1.52.178/cgi-bin/mapserv?mode=map&layer=elevation&mapext=
>> -180+-10+180+90&map=/var/mapserver/global/global.map&mapsize=500+250
>>
>> the outputmap has the wrong southernmost latitude.
>> It seems to be that something is overdefined.
>> Will the produced map whithin geographic coordinates expanded
>> to the width and height values of the bitmap or
>> will the geographic bounding box be recalculated ?
>>
>> Sincerely
>>
>> Ralf Puchert
>
> --
> Dr. Frank Lochter
> Data Centre
> GFZ Potsdam
> Telegrafenberg A3
> 14473 Potsdam
> fon. +49-331-288-1701
> fax. +49-331-288-1703
> url   http://www.gfz-potsdam.de/~marco
>



--
_______________________________________________________________
Rob Atkinson                        Email: rob at socialchange.net
Director
Social Change Online         Mob: 0419 202 973
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