Dataset API

You can find Geospatial Services, also known as Dataset API, on the dataset detail page for the selected dataset:
- Web Feature Service (WFS)
- Web Map Service (WMS)
- ArcGIS REST API (ARCGIS)

What are GeoSpatial Services?

GeoSpatial Services are application development or programming interfaces for users and developers to utilize the datasets provided on Common Spatial Data Infrastructure (CSDI) Portal in developing relevant application or programs for users in different aspects. The open standard Web Feature Service (WFS), Web Map Service (WMS) and ArcGIS rest service are provided under our Geospatial Services.

What are WFS, WMS and ArcGIS rest service?

WFS and WMS both follow the standards set by the Open Geospatial Consortium (OGC), an international standards organization that promotes and develops open standards for geospatial data and services.

With WFS, users can access vector data and perform various operations, such as querying, filtering, and data retrieval.

With WMS, users can access map images and display them in their web browser or desktop GIS software.

ArcGIS rest service is similar to WFS, which provides service using ESRI structure.

How do I access WFS, WMS and ArcGIS rest service on CSDI Portal?

To access the WFS, WMS and ArcGIS rest service, simply navigate to Metadata Page of an dataset and click GeoSpatial Service under Other Resources and Services Section. Select and click the service (WFS/WMS/ARCGIS) you wish to use. The Service URL will be copied automatically.

How do I customize my WFS/WMS/ArcGIS rest service request based on the copied URL?

Please select WFS/WMS/ArcGIS rest service for details:

WFS URL Format

https://[WFS URL]?[SERVICE]&[VERSION]&[REQUEST]&[TYPENAME]&[OUTPUTFORMAT]&[SRSNAME]&[BBOX]&[COUNT]

WFS Example URL

https://portal.csdi.gov.hk/server/services/common/landsd_rcd_1648571595120_89752/MapServer/WFSServer?service=WFS&version=2.0.0&request=GetFeature&typename=GEO_PLACE_NAME&outputFormat=GeoJSON&srsname=EPSG:4326&bbox=22.262474243164064,114.1035038986206,22.32152575683594,114.25302095794677&count=100

WFS Query Parameters

Parameter	Sample Value	Description
SERVICE	WFS	Service name. Value is “WFS”.
VERSION	2.0.0	Service version. Values are “1.0.0”, “1.1.0” & “2.0.0” (recommended).
REQUEST	GetFeature	Requested operation. Typical values are "GetFeature", “GetCapabilities”, etc.
TYPENAME	GEO_PLACE_NAME	Collection of feature instance(s) to be returned. TYPENAMES can be obtained via “GetCapabilities”.
OUTPUTFORMAT	GeoJSON	The returned data format. Common formats include “GeoJSON”, “GML32”, “CSV”, etc.
SRSNAME	EPSG:4326	Spatial Reference System. Supported values are “EPSG:4326” and “EPSG:2326”.
BBOX#	22.262474243164064, 114.1035038986206, 22.32152575683594, 114.25302095794677	Bounding Box. Values should be in the format of “minx,miny,maxx,maxy”.
COUNT#	100	Number of features to be returned. The maximum value is “10,000”.

# Optional Parameters

Sample Source Code and Preview

WMS Query Parameters

Parameter	Sample Value	Description
SERVICE	WMS	Service name. Value is “WMS”.
VERSION	1.3.0	Service version. Values are “1.0.0”, “1.1.0” ,“1.1.1” & “1.3.0” (recommended).
REQUEST	GetMap	Requested operation. Typical values are "GetMap", “GetCapabilities”, etc.
LAYERS	0	Layer(s) to be displayed. Layer names can be obtained via “GetCapabilities”.
FORMAT	image/png	Image format to be returned. Typical values are “image/png”, “image/jpeg”, “image/tiff”, etc.
TRANSPARENT#	TRUE	Image transparency. Values are “TRUE” or “FALSE”.
STYLES		Styles. Leave this value blank if no style to specify.
WIDTH	871	Pixel width of the image to be returned.
HEIGHT	344	Pixel height of the image to be returned.
CRS	EPSG:4326	Coordinate Reference System. Supported values are “EPSG:4326” and “EPSG:2326”.
BBOX	22.262474243164064, 114.1035038986206, 22.32152575683594, 114.25302095794677	Bounding Box. Values should be in the format of “minx,miny,maxx,maxy”.

# Optional Parameters

ArcGIS rest service Query Parameters

Parameter	Sample Value	Description
layerId	0	The target layer ID of ArcGIS rest service
f	geojson	The response format. Values: json \| geojson
returnGeometry#	true	If true, the result set includes the geometry associated with each result. The default is true.
spatialRel#	esriSpatialRelIntersects	The spatial relationship to be applied on the input geometry while performing the query. The supported spatial relationships include intersects, contains, envelope intersects, within, and so on. Values: esriSpatialRelIntersects \| esriSpatialRelContains \| esriSpatialRelCrosses \| esriSpatialRelEnvelopeIntersects \| esriSpatialRelIndexIntersects \| esriSpatialRelOverlaps \| esriSpatialRelTouches \| esriSpatialRelWithin \| esriSpatialRelRelation
geometry	{ "xmin":790055.3340887552, "ymin":820490.2153311807, "xmax":829191.0925707127, "ymax":859625.9738131382, "spatialReference": { "wkid":2326 } }	The geometry to apply as the spatial filter. The structure of the geometry is the same as the structure of the JSON geometry objects returned by the ArcGIS rest service. In addition to the JSON structures, for envelopes and points, you can specify the geometry with a simpler comma-separated syntax. Syntax: geometryType=esriGeometryEnvelope&geometry={xmin: -104, ymin: 35.6, xmax: -94.32, ymax: 41} geometryType=esriGeometryEnvelope&geometry=-104,35.6,-94.32,41 geometryType=esriGeometryPoint&geometry=-104,35.6
geometryType#	esriGeometryEnvelope	The type of geometry specified by the geometry parameter. The geometry type can be an envelope, point, line, or polygon. The default geometry type is an envelope. Values: esriGeometryPoint \| esriGeometryMultipoint \| esriGeometryPolyline \| esriGeometryPolygon \| esriGeometryEnvelope
inSR#	2326	The spatial reference of the input geometry. Values: 2326 \| 4326 \| 3857
outSR#	4326	The spatial reference of the output geometry. Values: 2326 \| 4326 \| 3857
where#	DISTRICT LIKE 'TW'	A WHERE clause for the query filter. Any legal SQL WHERE clause operating on the fields in the layer is allowed.
outFields#	*	The list of fields to be included in the returned result set. This list is a comma-delimited list of field names. If you specify the shape field in the list of return fields, it is ignored. To request geometry, set returnGeometry to true. You can also specify the wildcard "*" as the value of this parameter. In this case, the query results include all the field values.

# Optional Parameters

How do I work with the data returned by a WFS/WMS/ArcGIS rest service request?

You can work with the data returned by a WFS/WMS/ArcGIS rest service request using a compatible software tool, such as a GIS or web mapping application. You can also use a variety of analysis and visualization tools to explore and analyze the data further.

You can refer to the following page for instructions on how to add and visualize WFS, WMS and ArcGIS rest service data in QGIS using the specified WFS/WMS URL.

Adding WFS, WMS and ArcGIS rest service to QGIS

Where can I find documentation and tutorials for using WFS, WMS and ArcGIS rest service?

You can use the information and sample source code on this page as a reference while using WFS, WMS and ArcGIS rest service. For further technical information on WFS, WMS and ArcGIS rest service, you may make reference to the following OGC/ArcGIS standards.

OGC Standard - Web Feature Service (WFS)
OGC Standard - Web Map Service (WMS)
ArcGIS rest service

You may also see following technical guides.

OGC e-Learning - Data Access Standards WFS
OGC e-Learning - Visualization Standards WMS
ESRI - Communicating with a WFS service in a web browser
ESRI - Communicating with a WMS service in a web browser
ESRI - Feature service

CSDI Portal provides Data Query Service (DQS). It provides a simple way to extract spatial data using an HTTP-based API. Developers can customize a query, preview the results, and extract data in JSON format.

You can compose a query string using dataset id and layer name. Additionally, you can refine the query string by specifying four parameters including bbox, limit of return records, offset, and data fields.
You can compose the query string by entering values for each parameters.
Once all parameters are configured, click the “Execute” button to view the results in GeoJSON format.
For more information, please watch the video “Introduction to Data Query Service”

Dataset API

Accessing dataset using our Geospatial Services

What are GeoSpatial Services?

What are WFS, WMS and ArcGIS rest service?

How do I access WFS, WMS and ArcGIS rest service on CSDI Portal?

How do I customize my WFS/WMS/ArcGIS rest service request based on the copied URL?

WFS URL Format

WFS Example URL

WFS Query Parameters

Sample Source Code and Preview

WMS URL Format

WMS Example URL

WMS Query Parameters

Sample Source Code and Preview

ArcGIS rest service

ArcGIS rest service Example URL

ArcGIS rest service Query Parameters

Sample Source Code and Preview

How do I work with the data returned by a WFS/WMS/ArcGIS rest service request?

Where can I find documentation and tutorials for using WFS, WMS and ArcGIS rest service?

Data Query Service

Using Data Query Service