[mapserver-commits] r12706 - trunk/docs/en/mapcache
svn at osgeo.org
svn at osgeo.org
Wed Oct 26 13:04:27 EDT 2011
Author: tbonfort
Date: 2011-10-26 10:04:27 -0700 (Wed, 26 Oct 2011)
New Revision: 12706
Removed:
trunk/docs/en/mapcache/grids.txt
Modified:
trunk/docs/en/mapcache/config.txt
trunk/docs/en/mapcache/index.txt
Log:
add doc for grids
Modified: trunk/docs/en/mapcache/config.txt
===================================================================
--- trunk/docs/en/mapcache/config.txt 2011-10-26 14:53:52 UTC (rev 12705)
+++ trunk/docs/en/mapcache/config.txt 2011-10-26 17:04:27 UTC (rev 12706)
@@ -22,8 +22,7 @@
<services>...</services>
</mapcache>
-Concepts
---------------------------------------------------------------------------------
+.. _mapcache_sources:
Source
================================================================================
@@ -234,6 +233,7 @@
+.. _mapcache_grids:
Grid
================================================================================
@@ -241,44 +241,167 @@
A grid is the matrix that maps tiles on an area, and consists of a
spatial reference, a geographic extent, resolutions, and tile sizes.
-There are for now two predefined grids you can use with "default" openlayers
-settings:
+Mandatory Configuration Options
+--------------------------------------------------------------------------------
-* the "WGS84" grid corresponds to the grid that openlayers will request if
- you use:
+* **<size>**: The width and height of an individual tile, in pixels. Must be
+ specified as to positive integers separated by a space character. The most
+ common entry for this is:
+
+ .. code-block:: xml
+
+ <size>256 256</size>
-.. code-block:: javascript
-
- var layer = new OpenLayers.WMS("foobar","http://myserver/mapcache",{LAYERS:layername});
+* **<extent>**: The geographical extent covered by the grid, in ground units (e.g.
+ meters, degrees, feet, ...). Must be specified as 4 floating point numbers
+ separated be spaces, order like minx, miny, maxx, maxy. The (minx,miny) point
+ defines the origin of the grid, i.e. the pixel at the bottom left of the bottom-
+ leftmost tile is always placed on the (minx,miny) geographical point.
-* the "g" grid corresponds to the case when you wish to overlay tiles on top of googlemaps:
+ The (maxx,maxy) point is used to determine how many tiles there are for each
+ zoom level.
+
+ .. code-block:: xml
+
+ <extent>-180 -90 180 90</extent>
-.. code-block:: javascript
-
- var options = {
- projection: new OpenLayers.Projection("EPSG:900913"),
- units: "m",
- maxResolution: 156543.0339,
- maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34,20037508.34) };
+* **<srs>**: The projection of the grid, usually given by it epsg identifier. The
+ actual meaning of the value put here isn't used directly by mapcache to compute
+ reprojections, it is only used to lookup which grid to use when receiving WMS
+ requests.
+
+ .. code-block:: xml
+
+ <srs>epsg:4326</srs>
- map = new OpenLayers.Map( 'map', options );
- var gmap = new OpenLayers.Layer.Google("Google Streets",
- {
- 'sphericalMercator': true,
- 'maxExtent': new OpenLayers.Bounds(-20037508.34,-20037508.34,20037508.34,20037508.34),
- visibility: true
- }
- );
+ .. note::
+
+ This is the value that is passed on to the :ref:`source <mapcache_sources>`
+ when requesting a tile that is not already cached for the current grid. You
+ must make sure that the source that is queried is capable of returning
+ image data for this srs.
- var wms = new OpenLayers.Layer.WMS(
- "WMS",
- "/mapcache",
- { layers: 'osm', },
- {
- gutter:0,
- ratio:1
- });
+* **<units>**: The ground units used by the grid's projection. This entry is not
+ used directly by mapcache aside from calculating scales for the WMTS capabilites
+ document. Allowed values are:
+ * **m**: meters
+ * **dd**: decimal degrees
+ * **ft**: feet
+
+ .. code-block:: xml
+
+ <units>dd</units>
+
+* **<resolutions>**: This is a list of resolutions for each of the zoom levels
+ defined by the grid. This must be supplied as a list of positive floating
+ point values, separated by a space and ordered from largest to smallest. The
+ largest value will correspond to the grid's zoom level 0. Resolutions are
+ expressed in "units-per-pixel", depending on the unit used by the grid (e.g.
+ resolutions are in meters per pixel for most grids used in webmapping).
+
+ .. code-block:: xml
+
+ <resolutions>0.703125000000000 0.351562500000000 0.175781250000000 8.78906250000000e-2 4.39453125000000e-2 2.19726562500000e-2 1.09863281250000e-2 5.49316406250000e-3 2.74658203125000e-3 1.37329101562500e-3 6.86645507812500e-4 3.43322753906250e-4 1.71661376953125e-4 8.58306884765625e-5 4.29153442382812e-5 2.14576721191406e-5 1.07288360595703e-5 5.36441802978516e-6</resolutions>
+
+
+Optional Configuration Options
+--------------------------------------------------------------------------------
+
+* **<srsalias>**: This tag can be specified multiple times, and allows the user
+ to add multiple srs entries for a given grid. This is especially usefull if
+ the epsg id for a given projection has evolved over time, or to support other
+ catalogues than the epsg one (which is the only catalog supported by the wms
+ specification).
+
+ .. code-block:: xml
+
+ <srs>EPSG:310024802</srs>
+ <srsalias>IGNF:GEOPORTALFXX</srsalias>
+ <srsalias>EPSG:310024001</srsalias>
+
+* **<metadata>**:
+
+ * **<title>**: The name of the grid, in human readable form. Appears in the
+ capabilities documents.
+
+ .. code-block:: xml
+
+ <title>This grid covers the area blah blah blah</title>
+
+ * **<WellKnownScaleSet>**: see the WMTS keyword. This will add a
+ WellKnownScaleSet entry to the WMTS capabilites document. It is up to the
+ user to make sure that the supplied resolutions for the grid actually match
+ the pre-defined WellKnownScaleSet.
+
+ .. code-block:: xml
+
+ <WellKnownScaleSet>urn:ogc:def:wkss:OGC:1.0:GoogleCRS84Quad</WellKnownScaleSet>
+
+
+Preconfigured Grids
+--------------------------------------------------------------------------------
+
+There are three predefined grids you can use without referencing them in the
+mapcache.xml file:
+
+* the "WGS84" grid corresponds to a grid where the whole world is rendered on
+ 2 times 1 256x256 pixel tiles at level 0 (i.e. the (-180,-90,180,90) extent
+ fits on a 512x256 image). It goes down to zoom level 17.
+
+ .. code-block:: xml
+
+ <grid name="WGS84">
+ <metadata>
+ <title>GoogleCRS84Quad</title>
+ <WellKnownScaleSet>urn:ogc:def:wkss:OGC:1.0:GoogleCRS84Quad</WellKnownScaleSet>
+ </metadata>
+ <extent>-180 -90 180 90</extent>
+ <srs>EPSG:4326</srs>
+ <units>dd</units>
+ <size>256 256</size>
+ <resolutions>0.703125000000000 0.351562500000000 0.175781250000000 8.78906250000000e-2 4.39453125000000e-2 2.19726562500000e-2 1.09863281250000e-2 5.49316406250000e-3 2.74658203125000e-3 1.37329101562500e-3 6.86645507812500e-4 3.43322753906250e-4 1.71661376953125e-4 8.58306884765625e-5 4.29153442382812e-5 2.14576721191406e-5 1.07288360595703e-5 5.36441802978516e-6</resolutions>
+ </grid>
+
+* the "g" grid corresponds to the case when you wish to overlay tiles on top of
+ googlemaps, and is the default tiling scheme used in webmapping applications.
+ This grid goes down to zoom level 18. Level 0 is a single 256x256 tile. This
+ grid's default srs is EPSG:900913 which is non-standard, but in wider use than
+ than its official EPSG:3857 entry.
+
+ .. code-block:: xml
+
+ <grid name="GoogleMapsCompatible">
+ <metadata>
+ <title>GoogleMapsCompatible</title>
+ <WellKnownScaleSet>urn:ogc:def:wkss:OGC:1.0:GoogleMapsCompatible</WellKnownScaleSet>
+ </metadata>
+ <extent>-20037508.3427892480 -20037508.3427892480 20037508.3427892480 20037508.3427892480</extent>
+ <srs>EPSG:900913</srs>
+ <srsalias>EPSG:3857</srsalias>
+ <units>m</units>
+ <size>256 256</size>
+ <resolutions>156543.0339280410 78271.51696402048 39135.75848201023 19567.87924100512 9783.939620502561 4891.969810251280 2445.984905125640 1222.992452562820 611.4962262814100 305.7481131407048 152.8740565703525 76.43702828517624 38.21851414258813 19.10925707129406 9.554628535647032 4.777314267823516 2.388657133911758 1.194328566955879 0.5971642834779395</resolutions>
+ </grid>
+
+* the "GoogleMapsCompatible" grid is nearly identical to the "g" grid, except
+ its default srs is EPSG:3857 instead of EPSG:900913.
+
+ .. code-block:: xml
+
+ <grid name="GoogleMapsCompatible">
+ <metadata>
+ <title>GoogleMapsCompatible</title>
+ <WellKnownScaleSet>urn:ogc:def:wkss:OGC:1.0:GoogleMapsCompatible</WellKnownScaleSet>
+ </metadata>
+ <extent>-20037508.3427892480 -20037508.3427892480 20037508.3427892480 20037508.3427892480</extent>
+ <srs>EPSG:3857</srs>
+ <srsalias>EPSG:900913</srsalias>
+ <units>m</units>
+ <size>256 256</size>
+ <resolutions>156543.0339280410 78271.51696402048 39135.75848201023 19567.87924100512 9783.939620502561 4891.969810251280 2445.984905125640 1222.992452562820 611.4962262814100 305.7481131407048 152.8740565703525 76.43702828517624 38.21851414258813 19.10925707129406 9.554628535647032 4.777314267823516 2.388657133911758 1.194328566955879 0.5971642834779395</resolutions>
+ </grid>
+
Tileset
================================================================================
Deleted: trunk/docs/en/mapcache/grids.txt
===================================================================
--- trunk/docs/en/mapcache/grids.txt 2011-10-26 14:53:52 UTC (rev 12705)
+++ trunk/docs/en/mapcache/grids.txt 2011-10-26 17:04:27 UTC (rev 12706)
@@ -1,10 +0,0 @@
-.. _mapcache_grids:
-
-********************************************************************************
-Tile Grids
-********************************************************************************
-
-:Author: Thomas Bonfort
-:Contact: tbonfort at terriscope.fr
-
-TBD
Modified: trunk/docs/en/mapcache/index.txt
===================================================================
--- trunk/docs/en/mapcache/index.txt 2011-10-26 14:53:52 UTC (rev 12705)
+++ trunk/docs/en/mapcache/index.txt 2011-10-26 17:04:27 UTC (rev 12706)
@@ -22,7 +22,6 @@
caches
formats
dimensions
- grids
featureinfo
proxying
tile_assembling
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