[mapserver-users] MapServer Projections and Extents Tutorial

[Rahkonen Jukka (MML)]

Hi,

The other side is that hand written extents tend to go wrong every now and then, layer data and extents may change over the time, and for some data sources it is not heavy at all to read the extents on-the-fly. But big database tables without up-to-date statistics and Oracle in general can be awfully slow.

-Jukka Rahkonen-

Seth G wrote:


Thanks Tanya.

I'm going to run a few tests with a database connection to see what queries are generated to calculate the layer extents for WMS/WFS, and then may make a suggestion to update the MapServer docs.

Seth

On 02/11/2016 22:12, TC Haddad wrote:
Hi Seth,

I do agree that it should be *highly* recommended to set the extents of each LAYER, as people are often unaware what a huge speed advantage it is to have this already set. I found it to be particularly true for WFS.

I believe you should set the layer extents in the native coordinates of the layer, and let Mapserver take it from there.

Tanya

On Wed, Nov 2, 2016 at 11:38 AM, Seth G <geographika at gmail.com<mailto:geographika at gmail.com>> wrote:
Hi all,

A draft tutorial has been completed on use of projections in MapServer: https://geographika.github.io/tutorial/quickstart/projections.html
Comments and feedback welcome. This relates to http://mapserver.org/development/rfc/ms-rfc-115.html

There are a couple of things I came across that are still unclear to me relating to extents.

  *   Setting the EXTENT for a map has no effect when accessing via WMS, apart from the BoundingBox of the GetCapabilities metadata. Data is not restricted/limited.Not setting this leaves the MAP level BoundingBox extent as -1,-1,-1,-1. Should the MAP EXTENT have any other effects?

  *   The help for LAYER EXTENT states "In most cases you will not need to specify this, but it can be used to avoid the speed cost of having MapServer compute the extents of the data" - however all BoundingBox extents for each layer are automatically calculated from the source data in the WMS GetCapabilities request. I presume this could become quite slow with more and more layers. Is it/should it be recommended to manually set these (either with wms_extent in the LAYER METADATA or using LAYER EXTENT)?

Thanks for any clarifications on the above.

Regards,

Seth
--
web: http://geographika.co.uk
twitter: @geographika

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