Author: Roman

The GIS service

GIS services expose encapsulated GIS functions through Web interfaces and provide them to the client applications. Developers are often exposed to the use of services at this level.

ArcGIS Server service

Common services include MapServer (Dynamic map service/Slice map service) and FeatureServer (Feature Service).

Dynamic map service

The map server generates map data images in real time according to the request parameters

Commonly used data are map range, display layer, image size. As shown in figure:

Slice map service

Now more and more map services use tile technology, the basic map we are in contact with the base map is tile map. The tile map pyramid model is a multi-resolution hierarchical model, from the bottom of the tile pyramid to the top, the resolution is lower and lower, but the geographical range of the representation remains the same.

Slicing service features

  1. Has a unique tile class and tile row number
  2. The higher the tile level, the more tiles that make up the map, the more detailed the information that can be seen
  3. The tiles of a tile level map are made up of four tiles cut from each tile of the lower level, forming a tile pyramid

Slice service compared to dynamic map service

  1. Since the images in slice map service do not need to be generated by the server in real time, they are stored on the hard disk of the server, so the performance of the server is greatly improved.
  2. Slice map service has limited functions due to the pre-existence of images, such as the inability to hide a layer in the service.

Slice the storage

  1. Loose (unencrypted)

  1. The row and column number of the compact (encrypted) slicing service

Elements of the service

Used to publish the element layer in the spatial database, and support the operation of adding, deleting, checking and changing the element of the layer.

GeoServer

Usually, we use GeoServer to publish OGC standard services. GeoServer (Geographic Information System Server) is the J2EE implementation of OpenGIS Web server specification. It can easily publish map data by using GeoServer.

Common service types are WMS,WMTS,WFS, and WCS

Web Map Service (WMS)

A method of presenting spatial information in the form of maps. This specification defines three operations:

GetCapabitities, GetMap, GetFeatureInfo. GetCapabitities returns service-level metadata;

GetMap is used to return a map image whose geographic reference coordinates have been defined.

GetFeatureInfo is an optional parameter that returns special features that can be represented on a map.

Web Map Tile Service (WMTS)

WMTS is a cache technical standard proposed by OGC. It cuts the map into tiles of different sizes on the server side. This greatly reduces the load on the server side, making it less stressful, so that the user can have a better experience when using it.

WMTS uses tile matrix to cut the map. A map is cut into multiple tiles, and each tile has a unique identifier. These tiles have different resolutions.

The WMTS interface supports three types of resources:

  1. ServiceMetadata (ServiceMetadata) resources: describes the functions performed by the server and the specific information it contains.

  2. A map block resource represents a small piece of map information expressed on a layer in a map collection.

  3. The FeatureInfo resource returns information about a feature element in a map at a specific pixel location in the corresponding block.

Web Feature Service (WFS)

This service returns map images at the graph level.

The specification defines five operations: GetCapabilites, DescribeFeatureType, GetFeature, Transaction, and LockFeature.

  • GetCapabilites returns to the Web server to trace documents;

  • DescribeFeatureType returns an XML document that describes the structure of relevant elements that provide services;

  • GetFeature returns a service that is an instance of the element provided by the address request;

  • Transaction services Transaction requests;

  • LockFeature is an operation to lock an element type instance. It is used to lock an element instance when multiple transactions operate on the same element.

Web Coverage Service (WCS)

The main function of this service specification is to publish and share image data containing spatial location on the network.

The service consists of three operations: GetCapabilities, GetCoverage, and DescribeCoverageType.

  • GetCapabilities returns an XML document that describes the service and data set. Its main function is to determine the type of query, the type of data, and whether the acquired data is operable before it is executed.

  • The GetCoverage operation is executed after the GetCapabilities operation;

  • DescribeCoverageType Returns a complete description of the map layer based on the client’s operation requirements.

Static resource data services

GIS static resource data, such as tiles, terrain, 3dtiles, etc., can also be published using HTTP containers (such as IIS,TOMCAT,Nginx,Node, etc.) in addition to GIS server.

This method is simple and convenient, and the service efficiency is high

Internet online map service

The use of maps has exploded in recent years. Frequent use of mapping apis, such as Google Maps, Autonavi, Bing Maps, etc. These map services make the public access to a large amount of geographic data, and also promote the development of GIS industry.

The characteristics of

  1. High real-time data
  2. High data accuracy
  3. Comprehensive service types
  4. Various styles of products

Map world

Map Heaven and Earth is the “national geographic information public service platform” built by the National Bureau of Surveying, Mapping and Geographic Information. As the official geographic information service website in China. At present, it is the only public service platform with standard coordinate system and authoritative and credible data in China. The main service standards are issued to OGC standard.