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Implementing MapServer As Web Map Service (WMS) Applications for Spatial Data Sharing and Interoperability Case Study at Center For Marine Resources Surveys, National Coordinating Agency For Surveys And Mapping (BAKOSURTANAL)
 Suseno E-mail: seno@bakosurtanal.go.id |
 Ati Rahadiati E-mail: ati@bakosurtanal.go.id. |
Data spatial productions at center for marine resources surveys and another center at Bakosurtanal are growing rapidly. The integration each center / unit are not satisfactory made yet. The integration capabilities of a Spatial data allow disparate data sets to be brought together to create a complete picture of a situation. Peoples and Organizations are waiting for spatial data that Bakosurtanal produced.
The contribution of spatial data to society and people's life is not satisfactory made yet. Spatial data needs to be shared as soon as possible to accelerate and supporting government and organization for decision making and sustainable social and economic development, but it is difficult to implement due to the heterogeneity of spatial data. Therefore, web service based solution to facilitate the integration and share of spatial data
MapServer as open source (free) software are able to make spatial data sharing and integration enables. Customizing Mapserver as Web Map Services (WMS) made spatial data can be accessed over the Internet. With this, accessibility, integrity and interoperability enables the integration of data between organizations and across applications and industries, resulting in the generation and sharing of more useful information.
1. INTRODUCTION
National Spatial Data Infrastructure (NSDI) has been establish in Indonesia in the last decade. Each department has been seriously take action on their contribution in NDSI. Bakosurtanal as NSDI initiator and coordinator survey and mapping for spatial data producer also developing internal Spatial Data Infrastructure (SDI) supported by each center.
Each center focus on spatial data productions, data processing and data analysis but the integration are not satisfactory made yet before. This situation are contradictory that on the one hand the huge funds was spent and the large volume of spatial data was produced, on the other hand proper or usable data was scarce or data could not be shared or interoperated because of data itself. Today, Each Center are developing spatial data sharing and interoperability applications enables using various technology.
Society, departments and organizations are waiting for spatial data that Bakosurtanal produced. On high speed technology era spatial data sharing and interoperability should not be a huge problems, Internet protocol can be a solutions for this reason. Center for Marine Resources, one of centers at Bakosurtanal in supporting SDI made a great progress by developing web map service for spatial data sharing. This paper expose method spatial data sharing and interoperability enable over the internet.
2. Approach
The technical implementation of spatial data sharing and interoperability include three methods, namely data format exchange method, direct data access method and the Open Geo-data Interoperability Specification (OGIS) -based method. These three technical methods are in the different application field respectively and are improved constantly (Feng Wang).
In this discussion, OGIS - based method will only be exposes. OGIS was founded by Open GIS Consortium (OGC) in 1996 and the aim was to transparently get geographic data needed by end users in a heterogeneous distributed environment.
Web Service and XML have become mainstream technique to construct platform-spanned heterogeneous application and data exchange. Web services interoperate (communicate) through an XML-based protocol known as Simple Object Access Protocol (SOAP). This is an XML API to the functions provided by a Web service. Each Web service "advertises" its SOAP API using a mechanism called Web Services Description Language, allowing easy discovery of any service's capabilities.
Web services provide an open, interoperable, and highly efficient framework for implementing systems. They are interoperable because each piece of software communicates with each other piece via the standard SOAP and XML protocols.
3. System / Tools
There are several tools to create web service from free into commercial software. On This paper, Mapserver is the best choice on building Web Map Services (WMS). MapServer is an open source development environment for building spatially-enabled internet applications. It can run as a CGI program or via Mapscript which supports several programming languages.
4. An Implementation of Spatial Data as WMS
Mapserver that used to develop WMS is mapserver for windows (MS4W) and it run as CGI Program. Step by step to create WMS is :
a) Setting up Mapserver
WMS requests are handled by the "mapserv" CGI program. MS4W support already for this program. To access WMS server user need to complete HTTP URL including the http:// prefix, hostname, scriptname, potentially a "map=" parameter, and and terminated by "?" or "&".
Here is a valid online resource URL:
http://pssdal.bakosurtanal.go.id/cgi-bin/mapserv.exe?map=kodt.map&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetCapabilities
By creating a wrapper script on the server it is possible to hide the "map=" parameter from the URL and then your server's online resource URL could be something like:
http:// pssdal.bakosurtanal.go.id/cgi-bin/map?
b) Mapfile
Each instance of WMS server needs to have its own mapfile. It is just a regular MapServer mapfile in which some parameters and some metadata entries are mandatory. Most of the metadata is required in order to produce a valid GetCapabilites output. GetCapabilities return an XML document with metadata of the Web Map Server's information.
NAME WMS-KODT
STATUS ON
EXTENT 117.76 0.74 118.50 1.19
SIZE 400 300
SHAPEPATH "/spasial/data/50000/"
IMAGECOLOR 255 255 255
FONTSET "/ms4w/apps/pssdalweb/spasial/etc/fonts.txt"
SYMBOLSET "/ms4w/apps/pssdalweb/spasial/etc/symbols.sym"
UNITS dd
WEB
IMAGEPATH "/ms4w/tmp/ms_tmp/"
IMAGEURL "/ms_tmp/"
METADATA
"wms_title" "Kutai Timur" ##required
"wms_onlineresource" "http://pssdal.bakosurtanal.go.id/cgi-bin/mapserv.exe?map=kodt.map&request=GetCapabilities&"
"wms_srs" "epsg:4326"
"wms_feature_info_mime_type" "plain/text"
END
END
PROJECTION
"init=epsg:4326" ##required
END
#
# Start of layer definitions
#
LAYER # Hidrologi
NAME hidr
METADATA
"wms_title" "Hidrologi" ##required
"wms_feature_info_mime_type" "plain/text"
END
DATA "hidr/hidr11"
STATUS ON
TYPE POLYGON
PROJECTION
"init=epsg:4326"
END
CLASS
NAME "Keterangan"
COLOR 190 198 97
OUTLINECOLOR 0 0 0
END
END # Hidrologi
.....
......
LAYER # Dissolved Oxygen Kutai Timur
Group "Dissolved Oxygen"
NAME diox1
METADATA
"wms_title" "Dissolved Oxygen" ##required
"wms_feature_info_mime_type" "plain/text"
"queryable" "true"
"searchfield" "DO"
"fields" "DO:DO"
END
DATA "diox/diox1"
STATUS ON
TYPE POINT
CLASS
TEMPLATE "ttt_query.html"
SYMBOL 7
SIZE 5
COLOR 128 0 128
OUTLINECOLOR 128 0 128
END
END # Dissolved Oxygen Kutai Timur
END # Map File
c) Testing
Mapfile have to check the XML capabilities returned by server to make sure nothing is missing. Using a web browser, access into server's online resource URL to which you add the parameters "SERVICE=WMS&VERSION=1.1.1&REQUEST=GetCapabilities" to the end, e.g.
http://pssdal.bakosurtanal.go.id/cgi-
bin/mapserv?map=diox.map&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetCapabilities& This should return a document of MIME type application/vnd.ogc.wms_xml, browser is likely going to prompt to save the file. Save and open it in a text editor and returned XML from the WMS server. If get an error message in the XML output then take necessary actions. If everything went well, you should have a complete XML capabilities document. Testing with real client to access a new WMS server.
5. WMS Snapshot
XML capabilities returned by server
Testing WMS using Real Client (ArcGIS)
Testing WMS using Real Client (GIS Portal)
6. Conclusion and future work
With WMS specification, it has become easy to publish and share any geo-spatial information on the Internet. WMS, which is currently popular in actual applications, basically creates maps (PNG – Portable Network Graphics, or JPEG formats) of the requested area, which standard browsers can render. Thus, users do not have to copy huge data sets to local systems. Spatial data sharing doesn’t made on WMS feature yet. For future work need to implement Web Feature Service (WMS) that returnig Geographic Markup Language, WFS supplies users with the geographic features that satisfy their filtering criteria.
References
Feng Wang, Yunfei Shi, Xuguang Qin, Huan Zhang, Spatial Data Sharing And Interoperability Based On Web Spatial Data Service And GML, ISPRS Workshop on Updating Geo-spatial Databases with Imagery & The 5th ISPRS Workshop on DMGISs
ESRI, 2005, Spatial Data Standards and GIS Interoperability, An ESRI White Paper
Mapserver, Documentation of MapServer, http://mapserver.gis.umn.edu/
Jeff McKenna, 2006, WMS Servers with MapServer, www.dmsolutions.ca
Maged N. Kamel Boulos; Kiyoshi Honda, 2004,Web GIS in Practice: Publishing Your Health Maps and Connecting to Remote WMS Sources Using the Open Source UMN MapServer and DM Solutions MapLab, http://www.medscape.com/viewarticle/524924