1.1. Introduction to MapServer#
MapServer is a real-time map publishing system based on the fat server/thin client mode. When the client sends a data request, the server processes the spatial data in real time and sends the generated data to the client. The core part of MapServer is the map operation module written in C language, and the implementation of many functions of MapServer itself depends on some open source or free libraries.
The core part of MapServer is the map manipulation module written in C language, and many of its functions rely on some open source or free libraries. Using the support of GEOS and OGR/GDAL for a variety of vector and raster data, the projection transformation is carried out in real time through the Proj.4 shared library. MapServer follows OGC series specifications and can integrate PostGIS and open source database PostgreSQL, and store and SQL query the geospatial data. Based on a series of client-side JavaScript APIs such as ka-map, MapLab, Cartoweb and Chameleon to support the transmission and expression of geospatial data, and comply with a series of WMS, WFS, WCS, WMC, SLD, GML and Filter Encoding formulated by OGC specification.
1.1.1. Development history of MapServer#
MapServer is an open source geospatial data rendering engine written in C language. It originated from the University of Minnesota (UMN), NASA and the Minnesota Department of Natural Resources (MNDNR) in the mid-1990s. A collaborative project - ForNet, and later the TerrSIP project. Government support played a big role in the early development of MapServer.
This is an open source software released under the MIT-style License for publishing spatial data and interactive map applications on the Web, supporting all major operating systems, including Windows, Linux, Mac OS X, etc. Its positioning is not to implement a full-featured GIS, but to provide most of the core GIS functions for Web applications.
In 1994, Steve Lime, the father of MapServer, and his MapServer were familiar to more people. MapServer is not isolated in its development and growth, but has been supported by many open source communities and open source enthusiasts. In November 2005, the MapServer Foundation was established with the aim of “promoting a professional open source network mapping development environment and community. Even though it initially focused on network mapping projects, it hopes to provide funding to other open source geographic information projects”, not only promotes the professional development of MapServer, but also promotes the development of the entire open source network mapping technology.
With the further development of open source geographic information system software and the further optimization of open source network mapping environment, in February 2006, the MapServer Foundation was officially renamed the Open Source Geospatial Foundation (OSGeo), and Autodesk added MapGuide as an open source code to the foundation. It will further promote the development of MapServer.
1.1.2. Characteristics of MapServer#
MapServer is a popular open source project for displaying dynamic spatial maps on the Internet. It has the following characteristics:
Support for displaying and querying hundreds of grid, vector and database formats. Supported vector formats: ESRI shapefiles, PostGIS, ArcSDE of ESRI, etc. (implemented by OGR library). Supported grid formats: TIFF/GeoTIFF, EPPL7, etc. (implemented through the GDAL library). For shapefile files, you can build a quad tree spatial index.
Ability to run on many different systems (Windows, Linux, Mac OS X, etc.)
Available in two ways: CGI (for CGI, Ajax, Flex developers) and MapScript (For Php, Java, C # developers), native CGI is the most efficient
Support for popular scripting languages and development environments (PHP, Python, Perl, Ruby, Java, .NET)
On-the-fly projection
High quality rendering model
The output of custom template is fully supported.
Many off-the-shelf open source application environments
MapFile is the core of MapServer. It organizes various map elements into a hierarchical object system, and define the data source, the data format used, user interaction and support for the OGC protocol.
Support the font standard TrueType jointly developed by Microsoft and Apple.
Block (tiled) vector and raster data are supported.
Automatic control of map elements (such as scale, legend, reference, etc.).
The image scale is adjusted automatically.
Generate thematic maps using logical or regular expressions.
Feature annotations (including dimension conflict resolution).
MapServer can be configured dynamically through URLs.
Dynamic projection transformation is supported.
Support for several Open Geospatial Consortium network specifications: WMS (client/server), non-transactional WFS (client/server), WCS (server only), WMC, SLD,GML and Filter Encoding.
In its most basic form, MapServer is an inactive CGI program on a Web server. When a request is sent to MapServer, it uses the information and Mapfile passed in the requested URL. Creates an image of the requested map, the request can return the legend, ruler, reference map and variable values passed by CGI.
Compared with the many WebGIS solutions provided by commercial enterprises, MapServer is an open source project. This means that you can use MapServer for free and have the right to modify, copy and redistribute it yourself, MapServer has many advantages as well:
MapServer is an open source real-time map publishing system based on fat server / thin client mode. When the client sends data requests, the server processes the spatial data in real time and sends the generated data to the client. The core part of MapServer is the map operation module written in C language, and many of its functions depend on some open source or free libraries.
Using GEOS, OGR/GDAL to support a variety of vector and raster data, real-time projection transformation through the Proj.4 shared library. At the same time, it also integrates PostGIS and the open source database PostgreSQL to store and query geospatial data, and supports the transmission and expression of geospatial data based on a series of client-side JavaScript APIs such as ka-map, MapLab, Cartoweb, and Chameleon. A series of specifications such as WMS, WFS, WCS, WMC, SLD, GML and Filter Encoding formulated by OGC.
MapServer creates a map image based on spatial information stored in a digital format. It can handle vector and raster data. MapServer can render more than 20 different vector data formats, including shapefile,PostGIS and ArcSDE geometric features OPeNDAP,Arc/Info coverage and Census TIGER files.
Not all information displayed on the map must be in vector format. For example, aerial or satellite photos of an area can be displayed behind the rendered vector data to understand more clearly how these vector elements relate to the characteristics of the real world. MapServer reads two grid formats natively: GeoTIFF and EPPL7. However, you can read more than 20 formats (including Windows bitmaps, GIF, and JPEG) through the GDAL package, although MapServer understands and can render these grid types, it cannot mark images with spatial information.
1.1.3. Components of MapServer#
One of the realization methods of WebGIS is to use Common Gateway Interface (CGI) technology. On the server side, the WebServer and the GIS spatial database are connected through the CGI application program, and the client side can query and analyze the spatial data only by using the browser [2]. The University of Minnesota in the United States provides a WebGIS solution: MapServer, which uses CGI technology.
MapServer is an open source WebGIS project developed in C language. It is a real-time map publishing system based on fat server / thin client mode. When the client sends data requests, the server processes the spatial data in real time and sends the generated data to the client.
MapServer supports a three-tier architecture:
Application layer: client browser
Middle tier: MapServer CGI module / scripting language + MapScript, Web server
Storage tier: GIS spatial database
A simple MapServer consists of the following parts, as shown in the figure:
Schematic of MapServer principle#
MapFile
Structured text configuration files for MapServer applications. It defines the field of the map and is used to tell MapServer where the data is and where to output the image. It also defines the map layer. Including their data source, projection and notation. It must have a .map extension, otherwise MapServer will not recognize it. MapFile files organize various map elements into a system of objects with hierarchical relationships. Data sources, data formats used, user interaction and support for the OGC protocol are also defined in MapFile. Objects included in MapFile and their hierarchical relationships:
Geographic Data
MapServer can take advantage of many types of geographic information data sources. The default is the ESRI data format, and other formats of data are also supported.
HTMLPages
It is the interface between the user and MapServer, usually located at the web root. In its simplest form, MapServer can be called to place a static map image on an HTML page. To make the map interactive, the image is placed on an HTML form on the page.
MapServer CGI
Binary executables. It can receive requests to return images, data, etc., located in the cgi-bin or scripts directory of the web server. The user of the WEB server must have execute permissions on these directories. For security reasons, they cannot be in the root directory of the web. By default, this program is called mapserv.
WEB/HTTP Server
The HTML page is provided when the user’s browser is hit. You need a working Web (HTTP) server. For example, Apache or Microsoft’s IIS, they are on the same machine where you installed MapServer.
1.1.4. Two modes of MapServer#
MapServer can be regarded as the general name of two independent modules: MapServer CGI module and MapScript module. On the server side, any module can be used to write WebGIS programs. However, they use the same configuration file MapFile.
MapServer can run in two different modes: CGI and MapScript. In CGI mode, MapServer runs as a CGI script in the Web server environment. This is easy to set up and produce fast, direct applications. In MapScript mode, you can access MapServer API from Perl,Python or PHP. The MapScript interface allows flexible, feature-rich applications that can still take advantage of MapServer’s template tools.
1.1.5. Comparison between MapServer and GeoServer#
MapServer and GeoServer are both widely used open source WebGIS tools. Both publish maps through the Internet and are often compared. MAPSERVER is also OGC-compliant WMS and non-transactional WFS, based on CGI and written in C++; GEOSERVER is written in Java (you need to install Java SDK (not JRE) to run it), based on servlet and using the struts framework.
Functionally: MapServer is weaker than GeoServer, QGIS and stronger than UDIG.
Efficiency: Mapserver’s support for WMS (Web Map service) is more efficient, while Geoserver is better at attribute queries combined with WFS (Web Feature service) specifications.
In addition to functional comparison, special attention should be paid to the technical selection during development. MapServer focuses on map service functions and can be used as project components (or even core components), but other functions need to be implemented by developers most of the time; GeoServer is a relatively complete suite, which can basically be used as a product after deployment and installation.
MapServer is not a full-featured GIS, it does not provide integrated DBMS (Database Management System) tools, it has limited analytical capabilities, and there are no georeferencing tools.
Which is better? It’s hard to tell, depending on how you want to publish your data and what language you’re better at using. Both are excellent and have excellent documentation and user base. GEOSERVER enables you to edit spatial data online and generate thematic maps. Maps are published in XML files. MAPSERVER is good at generating thematic maps and is more mature than ever. Maps are published through text configuration files.
Which one is more appropriate? I advocate using MapServer if you just publish the map and don’t allow modification, it’s easier to maintain. GeoServer was chosen because of wanting better features such as online editing and database support like PostgreSQL or Oracle spatial database, another advantage of GeoServer is that there is a free client software UDIG.
Characteristics of MapServer#
Provides two ways of working, the CGI way (for CGI, AJAX, FLEX developers) and the MapScript way (for Php, Java, C#, Python developers). The native CGI method is the most efficient, and with TileCache, large-scale map tile data can be quickly generated. Compared with commercial or open source platforms based on .Net and J2EE, MapServer is more suitable for high-load large-scale Internet map applications. MapServer is a map service software written based on C, which is faster than GeoServer written in JAVA. Moreover, the history of MapServer is longer than that of GeoServer, and even the performance of MapServer is comparable to that of commercial ArcIMS.
Characteristics of GeoServer#
GeoServer（http://geoserver.org/ ）is a J2EE compliant and implements the WCS, WMS and WFS specifications , supports TransactionWFS (WFS-T), and its technical core is the integration of the well-known Java-developed GIS tools GeoTools.
For spatial information storage, it supports ESRI Shapefile and spatial databases such as PostGIS, Oracle, and ArcSDE, and the output GML files meet the requirements of GML2.1.
Because it is pure Java, it is more suitable for complex environmental requirements, and because of its open source, development organizations can flexibly implement specific target requirements based on GeoServer, which are lacking in commercial GIS components.
As a pure Java implementation, GeoServer is deployed in application servers, such as Tomcat; its WMS and WFS components respond to requests from browsers or uDig to access configured spatial databases, such as PostGIS, OracleSpatial, etc., and generate Maps and GML documents are transferred to the client.
GeoServer has the following advantages:
Written in Java language, standard J2EE framework, based on servlet and STRUTS framework, supporting efficient Spring framework development;
Compatible with WMS and WFS features, support WFS-T specification;
Efficient database supports PostGIS, ShapeFile, ArcSDE,Oracle, MySQL, etc.
Support hundreds of projections;
Ability to output network maps to formats such as jpeg, gif, png;