From IOSN-InWent FOSS GIS & Sahana Training

Contents 1 Overview 2 Server Configuration 3 Map File Configuration 4 Configuring Openlayers

Overview

Sahana using GoogleMap or OpenLayer as a map source for it's GIS features. With OpenLayer framework we can fetch not only online maps from public map service (YahooMap, MultiMap etc.) but also from our own WMS (Web Map Service) server. We can build WMS server using the opensource MapServer. All we need is:

1. MapServer installed ($> sudo apt-get install mapserver-bin)
2. Map file (shapefile) or PostGIS database (For this example we'll use Map shapefile)
3. Some html files and configuration map (*.map)

Server Configuration

Roughly here are the structure of the web server directory (if we're using shapefile, not PostgreSQL/PostGIS):

/var/www/sahana
/var/www/mentawai
/var/www/mentawai/view.html
/var/www/mentawai/blablabla.map
/var/www/mentawai/(*.shp, *.shx, *.prj, *.dbf files)

Map File Configuration

File blablabla.map is the map file, to create it we can use qGIS, GRASS, MapBender etc. , example:

 MAP
   NAME 'Kemiringan Lereng'
   SIZE 550 400
   EXTENT 98.506380 -3.212124 100.579115 -0.929394
   UNITS dd
   SHAPEPATH '/var/www/mentawai'
   STATUS on
   IMAGECOLOR 255 255 255
   IMAGETYPE png24
   PROJECTION
    	"init=epsg:4326"
   END
   WEB
    MINSCALE 0
    TEMPLATE "/var/www/mentawai/view.html"
    IMAGEPATH "/var/www/tmp/"
    IMAGEURL "/tmp/"
    METADATA
     wms_title                        "View1"
     wms_onlineresource               "http://127.0.0.1/cgi-bin/mapserv?map=/var/www/mentawai/slope.map&"
     wms_srs                          "EPSG:4326"
    END #METADATA
   END  #WEB
   LAYER  #slope.shp
    NAME 'kelas_kemiringan'
    DATA kelas_kemiringan 
    METADATA
     gix_layername        "kelas_kemiringan"
     gix_layerfieldnames  "cat|label"
     gix_layerfieldalias  "Kategori|Kelas Slope"
     wms_abstract         "Kelas kemiringan Kepulauan Mentawai"
     wms_srs              "EPSG:4326 EPSG:32747"
     wms_title            "Kelas kemiringan"
     wms_latlonboundingbox "98.506380 -3.212124 100.579115 -0.929394"
    END  #METADATA
    TOLERANCE 3
    TOLERANCEUNITS pixels
    LABELCACHE on
    STATUS on
    TRANSFORM true
    TYPE polygon #BENTUK
    CLASS
     NAME 'kelas_kemiringan 1'
     TEMPLATE '/var/www/mentawai/view.html'
     EXPRESSION ([cat]=1)
     STYLE
       COLOR 66 150 220
       BACKGROUNDCOLOR 255 255 255
     END  #STYLE
    END #CLASS
    CLASS
     NAME 'kelas_kemiringan 2'
     TEMPLATE '/var/www/mentawai/view.html'
     EXPRESSION ([cat]=2)
     STYLE
       COLOR 66 150 0
       BACKGROUNDCOLOR 255 255 255
     END  #STYLE
    END #CLASS
    CLASS
     NAME 'kelas_kemiringan 3'
     TEMPLATE '/var/www/mentawai/view.html'
     EXPRESSION ([cat]=3)
     STYLE
     COLOR 66 0 220
     BACKGROUNDCOLOR 255 255 255
    END  #STYLE
   END #CLASS
  END  #LAYER

Configuring Openlayers

1. In menu Administration > Config Utils > Config Values, there's some OpenLayers configuration that we can adjust. This is the part where we define how many layer that we'd like to use.
   
2. By default Sahana only provides maximum 2 layers for WMS, but we can do a little hacks to create more than 2 layers:
   1. $> sudo gedit /home/username/sahana/mod/gis/conf.inc
   2. Copy and change the [2]'s part (duplicating to 3 or more for examples...)
   3. Before:
      ...
      $conf['ol_wms_2_description'] = ;
      $conf['ol_wms_2_name'] = 'VMap1';
      ...
   4. After:
      ...
      $conf['ol_wms_2_description'] = ;
      $conf['ol_wms_2_name'] = 'VMap1';
      ...
      $conf['ol_wms_3_description'] = ;
      $conf['ol_wms_3_name'] = 'VMap1';
      ...
3. By default Sahana also using JPG in some part of the WMS feature so sometimes we need to hack another file to change it to transparent PNG
   1. $> sudo gedit /home/username/sahana/mod/gis/plugins/openlayers/openlayers-fns.php
   2. (Mr. Dudi will posting the modified script on the mailing list, also there'll be some coordination with Sahana's main developer)