[mapserver-users] MapServer Tile Indexes

[Rahkonen Jukka (MML)]

Hi,


There seems to be 37800 aerial photos in my tileindex, 10000 x 10000 or 12000 x 12000 pixels each, and system works like a charm. I wouldn't call 69.2 GB as a massive dataset.

First thing to do is to stop using ASCII GRID which must be one of the most unsuitable formats for a web map service. Server must always open the whole image into memory because format does not support direct access to region of interest. Your mode=map requests puts Mapserver to read all your 466 ASCII GRID files into memory.

Convert your DSM files into tiled GeoTIFFs, create overviews, and set a reasonable maxscaledenom for the layer so that no more than 40 or so files are opened from the tileindex layer. Make a layer group and use some other layer at small scales. All this is FAQ and you should find lot of reading from the internet. The "Geoserver on steroids" presentations are good start. The challenge is the same for all server brands.

-Jukka Rahkonen-

Wright, Simon M wrote:

Dear All

I'm trying to use the MapServer Tile Indexes to create a map service, and ultimately a WMS, of some DSM data but am getting an Internal Server Error.

The DSM data are organised as 466 5 × 5 km rasters with a resolution of 1 × 1 m with a total size of 69.2 GB.  The data format is Esri ASCII GRID.

To test the use of Tile Indexes in MapServer I used the gdaltindex to create an index shapefile for just twenty of the 5 × 5 km rasters and created a basic map file:

MAP
       IMAGETYPE            PNG
       EXTENT               240000 100000 250000 150000
       SIZE                 400 2000
       PROJECTION
              "init=epsg:27700"
       END
       LAYER
              NAME          "tiled-rasters"
              STATUS        ON
              TILEINDEX     "/datastore/b81071f2-85b3-4e31-8506-cabe899f989a/b81071f2-85b3-4e31-8506-cabe899f989a_copy/index_file"
              TILEITEM      "location"
              TYPE          RASTER
              PROJECTION
                     "init=epsg:27700"
              END
       END
END


When I request an image of the map with the URL http://localhost:8080/cgi-bin/mapserv?map=/vagrant/maps/tiled-rasters.map&layer=tiled-rasters&mode=map I get an "Internal Server Error".

Therefore I created a second index shapefile using the gdaltindex tool that only contained one of the 5 × 5 km rasters and updated the map file to point to the second index shapefile.  When I request an image of the map I can see an image of the DSM data as expected.

Therefore, am I asking too much of the tile indexing approach in MapServer to work against a massive dataset - 69.2 GB in 466 raster datasets - or have MapServer users been able to get tile indexing too work in MapServer against large data volumes and can provide some guidance.

Many thanks in advance of any help that MapServer users can offer.



Best wishes, Simon.

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