Introduction to Web Datasource

The Web engine can directly access the services provided by WFS, WMS, WCS, REST and other Map Service providers. This kind of engine is to process the Web server that conforms to the industry standard on the network as the Datasource of SuperMap. Through it, the map and data published on the network can be completely combined with the map and data of SuperMap, and the application can be integrated into the technical system of SuperMap, thus expanding the application field of SuperMap data engine. The Web Data source is a read-only engine.

The desktop product supports the following WebData sources:

1.OGC Standard Service (W * S)

2. REST Services

3. Google Maps Service (GoogleMaps)

4. Map Service (MapWorld)

5. OpenStreetMap

6. Global Topographic Map Service

7. Examples of Services

OGC Standard Service (W * C)

OGC Concept Understanding

  • GML: Geography Markup Language, OGC's geography markup language, whose model uses OGC's simple object model to organize files based on XML syntax and file formats.
  • URI: Locate using the resource identifier. To open the OGC service using the desktop client, you need to enter the address of the request body, that is, the URI. It generally consists of three parts: the naming mechanism for accessing resources, the host name for storing resources, and the name of the resource itself, which is represented by a path. The path structure is: HTTP://< server >: < port >/iserver/services. Among
    • server: The server address of the Publich Service.
    • port: The port number of the Publich Service.
    • service component: The name of the configured service component or set of service components. For example, the Map service component map-world is configured by default for SuperMap iServer.
    • service interface: name of the service interface configured and bound by the service component. For example, SuperMap iServer is configured with the service interface of WMS version 1.1.1 by default, and its service interface name is wms111.
  • Version negotiation: Version Number Negotiation that there are different versions of OGC web service standards, which are identified by numbers. In general, the versions implemented or supported between the client and the server are often different, and version negotiation sets the rules for how to achieve version synchronization between the client and the server. The rules are as follows:
    1. If the server implements the version number requested by the client, the server must send the data for that version.
    2. If the client sends a higher version of the request that the server does not recognize, the server must send the highest version that is lower than requested version.
    3. If the client requests a version that is lower than all versions supported by the server, the server must send the lowest version it supports.
    4. If the client does not recognize the version returned by the server, it stops communicating with the server and requests a version that is less than version returned by the server and that the client recognizes.
    5. If a client requests a version that is lower than version supported by all servers, and the server responds with a minimum version of the server according to Rule 3, but the client still does not recognize the higher version, the client sends a request with a higher version than server responded with.
      6. The
    6. version negotiation process is repeated until a mutually agreed version is reached or the client decides that it is no longer able to interact with a particular server.

OGC Service Introduction

WMS (Web Map Service), or Web Map Service, which conforms to the WMS implementation specification developed by the OGC (Open Geospatial Consortium, Open Geospatial Consortium). This standard defines three operations for creating and displaying maps: GetCapabilities, GetMap, and Get FeatureInfo. The standard defines three main operations for creating and displaying maps, including:

At present Desktop support opens the following WMS versions:

WCS (Web Coverage Service, Web Overlay Service) service, which conforms to the WCS implementation specification developed by OGC (Open Geospatial Consortium, Open Geographic Consortium).

WCS is a specification defined by OGC to share Geographic Spatial Data on the Web in the form of "Coverage". "Coverage" refers to data that can return the value of any specified point in a form that is easy to input into the model. The WCS service implements the sharing of the raster Image Dataset in the form of "Coverage".

At present The desktop supports opening data for WCS version 1.0.0.

  • WMS Service
    1. Get Capabilities, which is used to get service-level metadata. This action is required.
    2. GetMap, the core operation for getting a map image with well-defined geospatial parameters and size. This action is required.
    3. Get FeatureInfo, which is used to get the information of some special features displayed on the map. This operation is optional.
    • WMS 1.1.1
    • WMS 1.3.0
  • WFS Service

    WFS (Web Feature Service): The Web Feature Service, which conforms to the WFS implementation specification developed by the OGC (Open Geospatial Consortium, Open Geographic Consortium). This standard is primarily used to return GML encodings at the feature level. WFS allows clients to retrieve GML encoded GeoSpatial Data from multiple network Feature Services. Different WFS clients support different character sets, so the Encode Type of the request body is inconsistent when the request is sent.

    Remark

    Currently, WFS Datasource only supports the Data Browse feature.

  • WCS
  • WMTS

    WMS Map Service can flexibly respond to various requests.Every time the client sends a request, the server will visualize the data in real time, and then return the results in the form of pictures.However, in the case of a large number of visits, frequent requests need to occupy a large amount of resources for calculation, resulting in a decline in responsiveness. In order to provide the responsiveness of Map Service, it is necessary to reduce the time of visualization processing on the server side, so there is a service that improves the responsiveness by caching, and WMTS is one of them.

    WMTS, a Web Map Tiles service (Web Map Tile Service) that conforms to the WMTS specification specified by the OGC. The WMTS standard defines operations that allow users to access Tile maps and is the first OGC service standard to support REST access.

    WMTS is a cache technology standard proposed by OGC, which provides a standardized scheme of Publish Map Service using predefined Tile. Cache the map which is cut into Tiles of a certain size on the server side, only provide the service of these pre-defined single Tiles to the client, and put more Data Processing operations such as layer overlay on the client, so as to alleviate the pressure of Data Processing on the GIS server side and improve the user experience.

    WMTS uses the Tile matrix set (Tile matrix set) to represent the cut map, as shown in Figure 1. A Tile is a matrix cell that contains geographic data. A map is divided into many Tiles according to a certain The size of tiles to form a Tile matrix. One or more Tile matrices constitute a set of Tile matrices. Different Tile matrices have different scales, and each Tile matrix is identified by the Tile matrix identifier (generally the serial number of the Tile matrix, the layer with the lowest resolution is the 0th layer, which is arranged upward in turn). WMTS stipulates that each layer can specify multiple Tile matrix sets, each Tile matrix set has its own coordinate reference system, and each Tile matrix in the Tile matrix set corresponds to each level of scale.

    of Tile matrices
    Figure 1: Set

    Each Tile matrix has the following characteristics:

    Each Tile in

    the Tile matrix is identified by the Tile's row number (TileRow) and column number (TileCol). The row and column values are calculated from the Tile where the upper left corner of the Tile matrix is located. The starting row and column values are (0, 0), which increase downward and rightward in turn, as shown in Figure 2.

    Figure 2: Tile matrix

    WMTS 1.0.0 supports three implementation models:

    Currently, KVP and REST implementations are provided.

    The resources

    that WMTS requests from the server can be either procedure-oriented or resource-oriented. From the process-oriented concept, WMTS 1.0.0 defines three operations: GetCapabilities, GetTile, and Get FeatureInfo, where Get FeatureInfo is an optional operation. From the resource-oriented concept, WMTS 1.0.0 defines three resources: ServiceMetadata, Tile (Tile Data), and FeatureInfo (Feature information). Corresponding to the Get Capabilities, Get Tile, and Get FeatureInfo operations respectively.

    1. If the WMTS service uses Basic username and password authentication, you need to add the parameter AUTHORIZATION = Basic in the URL.

      The proposal
    1. of WMTS The concept
    2. of WMTS
      • Use your own Tile size as a scale.
        • The width (TileWidth) and height (TileHeight) of each Tile, defined
      • by pixels, is the size of the Tile.
        • The Upper Left Coordinates of the
      • matrix bounding box (TileMatrixminX, TileMatrixmaxY).
        • The width (MatrixWidth) and height (MatrixHeight) of a matrix defined
      • in terms of tiles, such as the number of tiles.
      3. Implementation Model
    3. of WMTS
      • HTTP KVP (Key-Value Pair) mode
      • SOAP mode
      • REST mode
      1. Get Capabilities, which returns the service metadata, that is, the service capabilities and information content.
      2. Get Tile to return the Tile map (Tile).
      3. Get FeatureInfo, which returns the Feature information (FeatureInfo) displayed on the Tile map, is an optional operation.
    4. WMTS Special Instructions
  • TMS

    TMS (Tile Map Service): Slice Map Service, which conforms to the TMS specification specified by OGC, allows on-demand access to map slices, and supports Modify.

    TMS is a Tile that has been cut and stored on the service, which has higher performance and faster access. However, you cannot operate on a Tile that has already been cut.

 

For more information on OGC services, please refer to the OGC (Open Geospatial Consortium, Open Geospatial Consortium) specification, http://www.opengeospatial.org .

REST service

REST-Representational State Transfer (Representational State Transfer) is a software architecture style proposed by Dr. Roy Fielding in 2000. Web services with a RESTful architectural style are simpler and easier to use than replicated SOAP services. The RESTful service of SuperMap provides RESTful GIS service for GIS users.

REST emphasizes the view of the whole network from the perspective of resources, and the REST-based architecture is a resource-oriented Architecture (ROA). The resource may be specific data, and may also be a service that can implement some functions, the client application uses a Uniform Resource Identifier (URI) Unique identifier, and the client application uses the URI to obtain the expression of the resource. Obtaining these representations causes the client Application to make a state transition, that is, a representational state transition.

REST typically uses existing popular protocols and standards such as HTTP, URI, XML, and HTML. SuperMap UGC REST services have the following characteristics:

  1. Each resource provided by the server is Unique Identified by a URI, but a resource can be identified by multiple URIs.
  2. The REST service uses the standard methods of the HTTP protocol, including GET, POST, PUT, and DELETE methods, which respectively correspond to the four operations of the resource, namely, obtaining, creating, modifying, and deleting.
  3. Provide representation of resources in multiple formats, such as XML, JSON, HTML, and so on.
  4. All of the information that a REST service needs to process a resource request is contained within the request.

Google Maps Service (GoogleMaps)

For Google eMap Service, read-only, cannot create.

Google Maps is an electronic Map Service provided by Google, including vector maps, Remote Sensing Imagery of different resolutions, and some Terrain Data. The desktop is integrated with the Google Maps engine, and in the case of network connectivity, the Google Maps service can be accessed directly in the desktop product. Currently supports access to the following Map Types:

  • Roadmap: a standard roadmap, such as a normal map shown on the Google Maps mapping site.
  • Satellite: Satellite Image layer.
  • Terrain: a map used to display terrain and vegetation.
  • Hybrid: a hybrid layer containing Satellite Image and route map, and a transparent layer displaying main street and address names on the satellite image.

Google Maps website: http://maps.google.com.

Note: The current default Server Address http://maps.google.com may not be able to display the map normally in China. After opening, the map will be blank. However, foreign users can use this function normally.

For users in China, you can switch Server Address to http://www.google.cn/maps and try to access the map again.

Sky Map Service (MapWorld)

Map Service released for Sky Map. Read-only, cannot create.

Map Service is an authoritative, credible and unified geographic information service provided by the State Bureau of Surveying and Mapping for the public, and it is the most complete geographic information service website in China. The Sky Map website provides a large amount of basic geographic information resources, including Global's vector terrain service and Remote Sensing Imagery, National Area's map data, navigation Digital Map data, and some urban three-dimensional street view data. The desktop integrates the SkyMap engine. When the network is connected, the SkyMap Service can be directly accessed in the desktop product. Currently supported Layer types are:

  • BackgroundMap: a background layer, which can be used as a base map.
  • AnnoMap: Chinese annotation layer.
  • AnnoMapE: English annotation layer.
  • Terrain: Terrain Layer, Coordinate System is WGS _ 1984, which can be directly loaded into the scene for use.

Map website: www.tianditu.cn.

GEOVIS Earth

GEOVIS Earth is an online digital earth exploration portal for mass users, providing users with rich digital content and instant interactive experience with rich spatio-temporal Data browsing, analysis and interactive digital content capabilities. The GEOVIS Earth engine is integrated in the desktop, and the GEOVIS Earth service can be directly accessed in the desktop product when the network is connected. At present, GEOVIS Earth provides three Map Services: vector, image and terrain.

GEOVIS Earth website: https://geovisearth.com.

SIWEI earth

SIWEI earth provides the slice image service of one map in the global region. The data is processed by unified fusion and mosaic. It has the characteristics of strong consistency and high timeliness in image quality and color. It supports online operation service. Users can access and apply it through the browser without Download Data. The desktop integrates the SIWEI earth engine, and the SIWEI earth service can be directly accessed in the desktop product when the network is connected.

SIWEI earth website: https://siweiearth.com.

Kailide (CareLand)

The vector map provided by Kailide only has data in China, including administrative divisions at all levels, road networks, water systems, POI and other elements. The map uses Mercator coordinate system, the highest display level is 18, the elements are clear and complete, and it can be called as a service. The desktop is integrated with Kailide Map Engine, and in the case of network connectivity, Kailide Map Service can be directly accessed in the desktop product.

Kellett website: https://map.careland.com.cn.

Century Space Images

The Internet-based full-resolution image online application service provided by 21st Century Space Technology Application Co., Ltd. The data resolution of domestic land and some island areas is sub-meter level, and the shooting time is mainly in 2019 and 2020. The service uses Mercator Projected Coordinate System, the highest display level abroad is 7, and the highest display level in China is 18.

Century Zhiyun Remote Sensing ImageryOnline Services Platform Website: https://mapcube.21atcloud.com.cn.

Global Topographic Map Service

It can be divided into two categories: California Map service and Dark Topographic Map service. It is a global shading map provided in Raster Tile format. The global shading map based on global DEMs shows the ups and downs of the global surface by using shadows and color gradients. At the same time, the data of vegetation, towns, glaciers and wasteland are superimposed, which is convenient for users to directly use this map as a base map to show specific thematic elements.

The topographic map service is divided into ten Display Scales. In order to make the terrain Display Effects better, each Display Scale uses Terrain Data with different resolutions, which is resampled from DEMs with a resolution of 1800 m.

Where, California Map is the global light-color topographic map data; Dark Top ographic Map is the global blue-black topographic map data. The data can be viewed in a browser at the following address:

California Map：https://maptiles.supermapol.com/iserver/services/map-Hillshade/rest/maps/WorldTerrainBase

Dark Topographic Map：https://maptiles.supermapol.com/iserver/services/map-Hillshade/rest/maps/WorldTerrainBlueDark

Examples of services

Interested users can visit the following addresses to experience some of the services provided by the iServer server.