[mapserver-users] Make PROJECTION mandatory?

Jeff McKenna jmckenna at gatewaygeomatics.com
Mon Apr 27 13:30:15 PDT 2020


I do look forward to approving pull requests from all of the people 
talking now of doc updates ;)  I really look forward to this.  :)  -jeff



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



On 2020-04-27 5:04 p.m., Mark Volz wrote:
> Hello,
> Just to add in my two cents to this.
> 
> 1) I don’t think we should have to specify a projection at the <Map> and <Layer> level if they are the same as that would seem redundant to me.   However, it should be allowed if a user wants to specify the projection at both levels.
> 2) Perhaps it would be good form (but not required) to allow "PROJECTION NONE" to explicitly specify to any client that the scalebar, legend, static map, etc is not intended to be projected onto a particular part of the earth.
> 
> Thanks!
> Sincerely,
> Mark Volz, GISP
> 
> -----Original Message-----
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> Subject: mapserver-users Digest, Vol 147, Issue 28
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>     1. Re: Make PROJECTION mandatory? (Basques, Bob (CI-StPaul))
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Mon, 27 Apr 2020 19:16:52 +0000
> From: "Basques, Bob (CI-StPaul)" <bob.basques at ci.stpaul.mn.us>
> To: Steve Lime <sdlime at gmail.com>, Jeff McKenna
>          <jmckenna at gatewaygeomatics.com>
> Cc: Mapserver <mapserver-users at lists.osgeo.org>
> Subject: Re: [mapserver-users] Make PROJECTION mandatory?
> Message-ID:
>          <CH2PR09MB43948CAABF943E79676E9EB0F7AF0 at CH2PR09MB4394.namprd09.prod.outlook.com>
> 
> Content-Type: text/plain; charset="utf-8"
> 
> 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://linkprotect.cudasvc.com/url?a=https%3a%2f%2fgatewaygeo.com%2f&c=E,1,uRKu6N_CiiNLLVVq0e47_QXUkZM4g9vqte-aBcbYyDH1b7WnS1Ln_b1a9kqHV0iwGwOUs3KazTLN-kMthOESPP3PB65XPBsYDNo99uct63RwastB0y4d0JpRk50,&typo=1
> 
> 
> 
> 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://linkprotect.cudasvc.com/url?a=https%3a%2f%2fmapserver.org%2fma
>> pfile%2fprojection.html&c=E,1,0fhb3f14X4JnWaND9-ffdGhd-Dt86B_opKe9hGsU
>> rG9BAz5MAFfY4va3fbKeVLpkpU7_UF3pNaH-rfzX6lyAkuRFz_4jFWPHVTfeNvPEY5eLCH
>> yJIN7bQ1TIPip6&typo=1 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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