WFS AND WMS TIPS AND TRICKS

WFS and WMS were developed by the Open Geospatial Consortium (OGC), an international not for profit organization.

Web Map Services (WMS) is a standardized HTTP protocol used to styling & render data into a map (image) and perform identify operations.

Web Feature Services (WFS) is a standardized HTTP protocol used to access/query/analyze feature attributes.

Thanks to Michelle Douville for all her hard work on these services and documentation.

AUDIENCE
AGO Content Creators	Data Publishers	Data Custodians	Data Managers	Data Stewards	Metadata Editors

Resources
Request Types
Output Formats
Example Requests
Pagination
Sample Applications

RESOURCES

BC Data Catalogue Search Results for WMS

Links

Description of BC Government’s Web Mapping Frameworks and Services https://bcgov.github.io/bcwebmaps-options/ (available from here too https://developer.gov.bc.ca/?q=spatial )

Geoserver WFS Outputformat types are JSON, JSONP, GML(s), CSV, and Shapefile
- https://docs.geoserver.org/latest/en/user/services/wfs/outputformats.html
Geoserver CQL Filter
- https://docs.geoserver.org/stable/en/user/tutorials/cql/cql_tutorial.html#cql-tutorial
WMS/WFS can be accessed through existing application programming interfaces (API) such as Leaflet, ArcGIS API for Javascript, and Openlayers.
WMS/WFS can be accessed can be accessed via client applications suchs as ArcGIS Desktop/Pro and QGIS.
Don’t forget curl and wget!

REQUEST TYPES

Types of WMS Requests:

<GetCapabilities>
<GetMap> 
<GetFeatureInfo> 
<GetLegendGraphic>

Types of WFS Requests:

<GetCapabilities>
<DescribeFeatureType>
<GetFeature> 

WMS/WFS requests can be made for all layers or as a separate service each layer/feature class:

OUTPUT FORMATS

WMS Output Options

<Format>image/png</Format>
<Format>application/atom+xml</Format>
<Format>application/json;type=geojson</Format>
<Format>application/json;type=topojson</Format>
<Format>application/json;type=utfgrid</Format>
<Format>application/pdf</Format>
<Format>application/rss+xml</Format>
<Format>application/vnd.google-earth.kml+xml</Format>
<Format>application/vnd.google-earth.kmz</Format>
<Format>application/x-protobuf;type=mapbox-vector</Format>
<Format>image/geotiff</Format>
<Format>image/geotiff8</Format>
<Format>image/gif</Format>
<Format>image/jpeg</Format>
<Format>image/png; mode=8bit</Format>
<Format>image/svg+xml</Format>
<Format>image/tiff</Format>
<Format>image/tiff8</Format>
<Format>image/vnd.jpeg-png</Format>
<Format>text/html; subtype=openlayers</Format>
<Format>text/html; subtype=openlayers2</Format>
<Format>text/html; subtype=openlayers3</Format>

WFS Output Options

<ows:Value>application/gml+xml; version=3.2</ows:Value>
<ows:Value>GML2</ows:Value>
<ows:Value>HTML</ows:Value>
<ows:Value>KML</ows:Value>
<ows:Value>SHAPE-ZIP</ows:Value>
<ows:Value>application/json</ows:Value>
<ows:Value>application/vnd.google-earth.kml xml</ows:Value>
<ows:Value>application/vnd.google-earth.kml+xml</ows:Value>
<ows:Value>csv</ows:Value>
<ows:Value>gml3</ows:Value>
<ows:Value>gml32</ows:Value>
<ows:Value>json</ows:Value>
<ows:Value>text/javascript</ows:Value>
<ows:Value>text/xml; subtype=gml/2.1.2</ows:Value>
<ows:Value>text/xml; subtype=gml/3.1.1</ows:Value>
<ows:Value>text/xml; subtype=gml/3.2</ows:Value>

EXAMPLE REQUESTS

WMS `GetMap` Example:

http://openmaps.gov.bc.ca/geo/pub/ows?
SERVICE=WMS&
VERSION=1.1.1&
REQUEST=GetMap&
FORMAT=application/openlayers&
TRANSPARENT=true&
STYLES=1748&
LAYERS=pub:WHSE_FOREST_VEGETATION.VEG_COMP_LYR_R1_POLY&
SRS=EPSG:3005&
WIDTH=512&HEIGHT=440&
BBOX=1069159.051186301%2C1050414.7675306%2C1074045.5446851396%2C1054614.0978811644

WFS `GetFeature` Example:

http://openmaps.gov.bc.ca/geo/pub/ows?
service=WFS&
version=2.0.0&
request=GetFeature&
typeName=pub:WHSE_CADASTRE.PMBC_PARCEL_FABRIC_POLY_SVW&
count=1&
outputFormat=json

Response in JSON:

{"type": "FeatureCollection","features": [{"type": "Feature","id": "WHSE_CADASTRE.PMBC_PARCEL_FABRIC_POLY_SVW.fid--7b8e502a_1677cdee8cf_498b","geometry": {"type": "Polygon","coordinates": [[[1121268.689,481286.634],[1121313.079,481348.863],[1121288.326,481374.623],[1121224.966,481286.119],[1121268.689,481286.634]]]},"geometry_name": "SHAPE","properties": {"PARCEL_FABRIC_POLY_ID": 27,"PARCEL_NAME": "006620256","PLAN_NUMBER": "VIP1993","PIN": null,"PID": "006620256","PID_NUMBER": 6620256,"PARCEL_STATUS": "Active","PARCEL_CLASS": "Subdivision","OWNER_TYPE": "Private","PARCEL_START_DATE": null,"MUNICIPALITY": "Parksville, City of","REGIONAL_DISTRICT": "Regional District of Nanaimo","WHEN_UPDATED": "2016-04-21Z","FEATURE_AREA_SQM": 3260.4354,"FEATURE_LENGTH_M": 264.7362,"OBJECTID": 77398905,"SE_ANNO_CAD_DATA": null}}],"totalFeatures": 1573818,"numberMatched": 1573818,"numberReturned": 1,"timeStamp": "2018-12-05T06:06:21.364Z","crs": {"type": "name","properties": {"name": "urn:ogc:def:crs:EPSG::3005"}}}

Tip: Prettify JSON to make it easier to read.

More complex examples

WMS `GetMap`

Dams in the Cariboo District (CQL filter), output as GeoJSON:

http://openmaps.gov.bc.ca/geo/pub/ows?
SERVICE=WMS&
VERSION=1.1.1&
REQUEST=GetMap&
FORMAT=application/json;type=geojson&
LAYERS=pub:WHSE_WATER_MANAGEMENT.WRIS_DAMS_PUBLIC_SVW&
HEIGHT=1024&WIDTH=1024&
STYLES=3959&
SRS=EPSG:4326&
CQL_FILTER=%22DISTRICT_PRECINCT%22%20LIKE%20%27Cariboo%25%27&
BBOX=-139.46653152270716,39.3982201780243,-110.0651303636062,68.79962133712526

N.B. even for a JSON request, height and width must be specified. Weird, huh?

WMS `GetFeatureInfo`

i (or x) and j (or y) refer to the query point on the map

Land Parcel Information at a specified location, output as an HTML table:

https://openmaps.gov.bc.ca/geo/ows?
SERVICE=WMS&
VERSION=1.3.0&
REQUEST=GetFeatureInfo&
BBOX=48.40785014436799116,-123.36256681214997855,48.41958084268204487,-123.34925222208043749&
CRS=EPSG:4326&
WIDTH=538&HEIGHT=474&
LAYERS=pub:WHSE_CADASTRE.PMBC_PARCEL_FABRIC_POLY_SVW&
QUERY_LAYERS=pub:WHSE_CADASTRE.PMBC_PARCEL_FABRIC_POLY_SVW&
INFO_FORMAT=text/html&
I=109&
J=187&
FEATURE_COUNT=10

Crown Tenures within a bounding box, output as text:

https://openmaps.gov.bc.ca/geo/pub/WHSE_TANTALIS.TA_CROWN_TENURES_SVW/ows?
service=WMS&
request=GetFeatureInfo&
version=1.1.1&
layers=pub:WHSE_TANTALIS.TA_CROWN_TENURES_SVW&
styles=2214&
format=text/xml&
srs=EPSG:4326&
width=970&height=485&
bbox=-123.35,50.60393449638617,-123,51.593907018763396&query_layers=pub:WHSE_TANTALIS.TA_CROWN_TENURES_SVW&
feature_count=500&
x=50&y=50

WFS `GetFeature`

WELL_STATUS attribute and geometry of the Water Well with Well Tag # 65501, output as JSON:

http://openmaps.gov.bc.ca/geo/ows?
service=WFS&
version=2.0.0&
request=GetFeature&
typeName=WHSE_WATER_MANAGEMENT.GW_WATER_WELLS_WRBC_SVW&
outputFormat=application/json&
SrsName=EPSG:4326&
CQL_FILTER=WELL_TAG_NUMBER=65501&
PROPERTYNAME=WELL_STATUS

Major Cities that fall within a Vancouver Island bounding box, output as JSON:

https://openmaps.gov.bc.ca/geo/pub/ows?
SERVICE=WFS&
VERSION=2.0.0&
REQUEST=GetFeature&
outputFormat=json&
typeName=WHSE_BASEMAPPING.BC_MAJOR_CITIES_POINTS_500M&
SRSNAME=EPSG:3005&
CQL_FILTER=WITHIN%28GEOMETRY%2C%20POLYGON%20%28%28830772.7%20367537.4%2C%201202463%20367537.4%2C%201202463%20651616.7%2C%20830772.7%20651616.7%2C%20830772.7%20367537.4%29%29%29

The CQL_FILTER being applied is WITHIN(GEOMETRY,POLYGON((830772.7 367537.4, 1202463 367537.4, 1202463 651616.7, 830772.7 651616.7, 830772.7 367537.4))). In this case, URL encoding first is necessary to send the request.

Wells within 100 meters of a point:

https://openmaps.gov.bc.ca/geo/pub/ows?
SERVICE=WFS&
VERSION=2.0.0&
REQUEST=GetFeature&
outputFormat=application/json&
typeName=WHSE_WATER_MANAGEMENT.GW_WATER_WELLS_WRBC_SVW&
CQL_FILTER=DWITHIN(GEOMETRY,POINT(1161815%20452123),100,meters)

Community Health Service Area that intersects with a given point:

https://openmaps.gov.bc.ca/geo/pub/ows?
service=WFS&
version=1.0.0&
request=GetFeature&
typeName=pub:WHSE_ADMIN_BOUNDARIES.BCHA_CMNTY_HEALTH_SERV_AREA_SP&
srsname=EPSG:4326&
cql_filter=INTERSECTS(SHAPE,POINT(1224584.57951%20469989.94624))&propertyName=CMNTY_HLTH_SERV_AREA_NAME,LOCAL_HLTH_AREA_NAME,HLTH_SERVICE_DLVR_AREA_NAME,HLTH_AUTHORITY_NAME&
outputFormat=application/json

PAGINATION

Max number of feature limit and work-around for larger datasets

Most openmaps.gov.bc.ca services have a maximum of 10000. A WFS GetCapabilities request with version 2.0.0 will tell you what the maximum features limit is.

<ows:Constraint name="CountDefault">
<ows:NoValues/>
<ows:DefaultValue>10000</ows:DefaultValue>
</ows:Constraint>
</ows:Operation>

Drawing on the Geoserver docs:

Maximum number of features — Maximum number of features that a WFS GetFeature operation should generate, regardless of the actual number of query hits. A WFS request can potentially contain a large dataset that is impractical to download to a client, and/or too large for a client’s renderer. Maximum feature limits are also available for feature types.”

How to find out if your request will exceed the limit? Add resulttype=hits to your WFS request (for environmental monitoring stations in this example):

https://openmaps.gov.bc.ca/geo/pub/ows?SERVICE=WFS&VERSION=2.0.0&REQUEST=GetFeature&outputFormat=csv&typeNames=WHSE_ENVIRONMENTAL_MONITORING.EMS_MONITORING_LOCN_GROUPS_SVW&propertyName=OBJECTID&resulttype=hits

The result will include: numberMatched="13641"

Alternatively, if you make the request without resulttype=hits and just so happen to get 10000 features returned, that’s a good hint you are hitting the limit.

If your request might exceed the feature limit, the solution is pagination - paging through the results in chunks in order to get all the features you are after.

Paging example

To page successfully, we must add three parameters to our request:

count (in WFS v2) or maxFeatures (in WFS v1) limiting features to return below the maximum
sortBy set to the primary key for the table (hopefully there is an ObjectID or similar attribute)
startIndex set to 0, but incrementing by the count value for additional requests

Returning to our monitoring station request with 13631 features, we can use a count of 5000, sorting by ObjectID, starting at index 0 (first request):

https://openmaps.gov.bc.ca/geo/pub/ows?
SERVICE=WFS&VERSION=2.0.0&
REQUEST=GetFeature&
outputFormat=csv&
typeNames=WHSE_ENVIRONMENTAL_MONITORING.EMS_MONITORING_LOCN_GROUPS_SVW&
propertyName=OBJECTID&
count=5000&
sortBy=OBJECTID&
startIndex=0

To get the next page, we increase the startIndex to 5000. And then finally increment to 10000 for the last page.

SAMPLE APPLICATIONS

OpenLayers Preview

Example of an Openlayers output format for preview and exploring:

http://openmaps.gov.bc.ca/geo/pub/ows?
SERVICE=WMS&
VERSION=1.1.1&
REQUEST=GetMap&
FORMAT=application/openlayers&
TRANSPARENT=true&STYLES=7738&
LAYERS=pub%3AWHSE_MINERAL_TENURE.HSP_MJR_MINES_PERMTTD_AREAS_SP&
SRS=EPSG:3005&
WIDTH=512&HEIGHT=441&
BBOX=1048725.4914577596%2C996424.7407280033%2C1068271.4654531137%2C1013222.0621302609

Leaflet Example App

A simple leaflet app that has some of the WMS parameters as URL parameters -
http://delivery.openmaps.gov.bc.ca/kml/m/lfg103/lfwmsi2.html?l=WHSE_MINERAL_TENURE.HSP_MJR_MINES_PERMTTD_AREAS_SP&s=7738&a=MINE_GUID&f=MINE_GUID%3D%27d214e340-4575-4225-8dde-4f9504d5748f%27

Add WMS Layers

var map = new L.Map('map', {
center: [52, -123.3],
zoom: 5
//layers: [mqLayer]
});
	 L.esri.tiledMapLayer({
url: 'http://maps.gov.bc.ca/arcserver/rest/services/province/roads_wm/MapServer',
maxZoom: 15
}).addTo(map);
	 // layer name parameter
var l = getURLParameters("l");
	 // style name parameter
var s = getURLParameters("s");
	 // filter attribute parameter
var a = getURLParameters("a");
	 // filter statement parameter
var f = getURLParameters("f");
var owsrootUrl = 'http://openmaps.gov.bc.ca/geo/ows';
var fclayer = L.tileLayer.wms(owsrootUrl, {
format: 'image/png',
transparent: true,
	styles: s,
layers: l
}).addTo(map);

Add WFS Layers and Zoom to

var parameterswfs = L.Util.extend(defaultParameterswfs);
 var URL = owsrootUrl + L.Util.getParamString(parameterswfs);
 var WFSLayer = null;
 var ajax = $.ajax({
  url : URL,
  dataType : 'jsonp',
  jsonpCallback : 'getJson',
  success : function (response) {
   
   WFSLayer = L.geoJson(response, {
     style: function (feature) {
         return {
         stroke: true,
         fillColor: '00FFFF',
         fillOpacity: 1
         };
     },
     onEachFeature: function (feature, layer) {
         popupOptions = {maxWidth: 200};
         // does this feature have a property named popupContent?
         if (feature.properties && feature.properties.popupContent) {
          layer.bindPopup(feature.properties.popupContent);
         }
     }
   });
            
   WFSLayer.addTo(map);
   console.log(response);

   var corner1 = L.latLng(response.features[0].properties.bbox[1], response.features[0].properties.bbox[0]);
   var corner2 = L.latLng(response.features[0].properties.bbox[3], response.features[0].properties.bbox[2]);
   bounds = L.latLngBounds(corner1, corner2);
   console.log(bounds)
   console.log(corner1)
   console.log(corner2)
   if (bounds) {
              map.fitBounds(bounds, {maxZoom: 15});

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