[mapserver-dev] MS RFC 107 again

Tamas Szekeres szekerest at gmail.com
Tue Aug 19 04:18:36 PDT 2014

Hi Devs,

This RFC <http://mapserver.org/development/rfc/ms-rfc-107.html> has been
abandoned a bit, but I'd like to see it in MapServer 7.0, too.
The proposed changes are fairly straightforward, but requires to modify
several files.

Up to this time we haven't found any compatible solution which would
satisfy with the client's need and would require smaller amount of
modifications, but the proposed changes have been implemented locally at
the client and works without problems for quite a long time.

Do we have any specific issues which would prevent me from calling a vote
on it?

Best regards,


2014-03-26 14:43 GMT+01:00 Tamas Szekeres <szekerest at gmail.com>:

> Hi Devs,
> We had a small discussion here in the codesprint, whether we should apply
> this RFC as it stands or not. In fact I understand that the proposed
> changes are fairly system wide, but let us review the issues that should
> anyway be handled in some way.
> I've also discussed with the client who has raised this problem
> originally, mainly to refresh my memory related to all aspects. It must
> also be added that applying the proposed changes in a local build could
> indeed solve all issues they had. So the problems are as follows:
> 1. Correction code should be applied at the client when using
> setExtent/getExtent in mapscript. This is fairly odd for most users who
> would prefer to go with the edge of pixel extent model. We could however
> provide variants for   setExtent/getExtent which mimics the  edge of pixel
> extent model at the interface.
> 2. The current code regarding to the geographical width yields incorrect
> result from the WMS side, which should probably be reverse corrected if the
> query has been originated from WMS specifically. Actually the user would
> expect to have the map drawn at the specified extent, but mapserver
> considers as if a smaller extent has been specified by the user. When using
> geo width dependent rendering (MINGEOWIDTH/MAXGEOWIDTH) the layers may
> unexpectedly be drawn at a given zoom level where it should not normally be
> drawn.
> 3. The user wants to draw a given extent, but actually a smaller amount of
> features are provided in the view. Given a large extent (like a whole
> continent) half pixel difference in each directions is not negligible
> 4. Smaller amount of features are retrieved from the database which the
> WMS client may expect. We should probably reverse correct the extent when
> setting the spatial filter against the database to get the correct set of
> the features drawn on the map.
> Lastly to add the other way to look at it is the original
> mapserver implementation for this is very, very old and not OGC compliant
> which is now the de-facto standard. It was originally done for a specific
> purpose as I understand it (integration with ERDAS reading the discussion
> related to this).
> Perhaps it is time to review this to be in line with OGC standards and the
> other mapping engines. Also I don't buy the argument about 'the effect on
> all existing map files out there' is a valid one. I don't think users would
> notice any difference. Besides the approach suggested have been
> configurable in the map file.
> Best regards,
> Tamas
> 2014-01-01 15:43 GMT+01:00 Tamas Szekeres <szekerest at gmail.com>:
>> Hi Devs,
>> Happy New Year All!
>> According to this thread
>> <http://osgeo-org.1560.x6.nabble.com/Questions-regarding-to-the-extent-scale-calculations-in-MapServer-td5091493.html>
>> I've ringed in to write an RFC about the proposed changes.
>> Please find RFC-107 for review submitted to the documentation tree:
>> http://mapserver.org/development/rfc/ms-rfc-107.html
>> Let me know about your suggestions.
>> Best regards,
>> Tamas
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