[mapserver-users] Make PROJECTION mandatory?

[Basques, Bob (CI-StPaul)]

All,

I can second Steve’s idea.  We were using Mapserver for years before we needed to pay attention to projections, because all of our data wasin our local coordinate system.   We now work projection across all map services for all layers, either by explicitly stating the projection or having it scripted at the web server call.  Some cases it won’t matter, if ever, and others it will be instrumental in getting a site working with many and varied projected datasets being combined.

I would agree that it should be a topic more prominently displayed/noted in the documentation.

Bobb


From: mapserver-users <mapserver-users-bounces at lists.osgeo.org> On Behalf Of Steve Lime
Sent: Monday, April 27, 2020 1:21 PM
To: Jeff McKenna <jmckenna at gatewaygeomatics.com>
Cc: Mapserver <mapserver-users at lists.osgeo.org>
Subject: Re: [mapserver-users] Make PROJECTION mandatory?

Think Before You Click: This email originated outside our organization.

I would prefer to pursue as a documentation/communication exercise first. It's not that I don't agree that PROJECTION blocks are generally recommended but making them required and introducing artificial projections to deal with cases when projections aren't used (embedded legends, scale bars and other static map elements) will touch a lot of code. It's also a major breaking change that would potentially break a large percentage of mapfiles going forward.

--Steve

On Mon, Apr 27, 2020 at 8:43 AM Jeff McKenna <jmckenna at gatewaygeomatics.com<mailto:jmckenna at gatewaygeomatics.com>> wrote:
Hi Jukka,

I personally consider defining PROJECTION blocks at the MAP level and
all LAYERs mandatory, in my day-to-day work, for each and every mapfile.
  If you do not specify all of these, MapServer makes assumptions and
you are just asking for trouble downstream through WMS clients etc.
(your users)

I also do not rely on any PROJECTION AUTO magic either, for my paying
clients.

These are all nice tricks but in critical production environments I stay
away from them; instead, find the source projection, and define the MAP
projection block and all LAYER projection blocks.

I'm not sure this answers your questions, but this was my 'gut reaction'
to your message.  I believe we have the same thinking here.

-jeff



--
Jeff McKenna
MapServer Consulting and Training Services
https://gatewaygeo.com/



On 2020-04-27 10:36 a.m., Rahkonen Jukka (MML) wrote:
> Hi,
>
> Recent Mapserver buids require PROJ and GDAL
> https://mapserver.gis.umn.edu/ja/development/rfc/ms-rfc-127.html. That
> means that every Mapserver can support PROJECTION blocks both at the MAP
> level and within LAYER. And because there are no more builds without
> Proj support there is no real need for writing mapfiles without
> PROJECTION blocks. Therefore I suggest that such mapfiles should be
> considered invalid in the future. If it is for some reason too strict
> requirement, what if we at least edit the documentation
> https://mapserver.org/mapfile/projection.html so that it really
> encourages users to write the PROJECTION blocks. GetCapabilities could
> also show something like
> <!-- WARNING: No explicit source projection defined for layer
> 'my_layer'. -->
>
> Having layers without PROJECTION saves users from writing this much text:
>
> “PROJECTION "init=epsg:3857" END
>
> but when the user meets any problem with accessing data or rendering the
> first thing to check is the projection. In the mailing list it means one
> more question-answer round before getting closer to the real problem –
> if the problem was not in the projection, as it very often is.
>
> If source data are in local coordinate system it would be better to
> define also that explicitly with a special keyword like PROJECTION “LOCAL”.
>
> Would other user consider making projection compulsory rather as an
> improvement or inconvenience?
>
> -Jukka Rahkonen-
>
>
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>


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