WMS — Web Map Service

The WMS (Web Map Service) allows you to render styled map tiles from GeoServer layers. This guide covers all five WMS operations and their parameters.

All requests go to: https://graph.quarticle.ro/graph/layers/wms/

Authentication: Add the Authorization: YOUR_API_KEY header to all requests.

GetCapabilities

Discover available layers, styles, projections, and output formats published in GeoServer.

Purpose: Metadata discovery — understand what layers are available and what operations they support.

Required Parameters

Parameter	Value	Example
`service`	`WMS`	`service=WMS`
`version`	`1.3.0`	`version=1.3.0`
`request`	`GetCapabilities`	`request=GetCapabilities`

Response

Returns an XML document listing all available layers with their:

Bounding boxes (spatial extent)
Available projections (SRS)
Styles
Data types

cURL
JavaScript
Python

curl -X GET "https://graph.quarticle.ro/graph/layers/wms/GetCapabilities" \
  -H "Authorization: YOUR_API_KEY" \
  --data-urlencode "service=WMS" \
  --data-urlencode "version=1.3.0" \
  --data-urlencode "request=GetCapabilities"

const apiKey = process.env.QARTA_API_KEY;

fetch('https://graph.quarticle.ro/graph/layers/wms/GetCapabilities?' +
  new URLSearchParams({
    service: 'WMS',
    version: '1.3.0',
    request: 'GetCapabilities'
  }), {
  headers: { 'Authorization': `${apiKey}` }
})
  .then(r => r.text())
  .then(xml => {
    // Parse XML document
    const parser = new DOMParser();
    const doc = parser.parseFromString(xml, 'text/xml');
    const layers = doc.querySelectorAll('Layer');
    console.log(`Found ${layers.length} layers`);
  });

import requests
import xml.etree.ElementTree as ET

api_key = os.getenv('QARTA_API_KEY')

response = requests.get(
  'https://graph.quarticle.ro/graph/layers/wms/GetCapabilities',
  params={
    'service': 'WMS',
    'version': '1.3.0',
    'request': 'GetCapabilities'
  },
  headers={'Authorization': f'{api_key}'}
)

root = ET.fromstring(response.text)
layers = root.findall('.//{http://www.opengis.net/wms}Layer')
print(f'Found {len(layers)} layers')

DescribeLayer

Get metadata about a specific layer's WFS or WCS source.

Purpose: Find the corresponding WFS typeNames parameter for a WMS layer.

Required Parameters

Parameter	Description
`service`	`WMS`
`version`	`1.1.1`
`request`	`DescribeLayer`
`layers`	Comma-separated layer names. Example: `GRAPHRASTER:light_pollution`

Optional Parameters

Parameter	Description
`exceptions`	Exception format. Default: `application/vnd.ogc.se_xml`

Example

cURL

curl -X GET "https://graph.quarticle.ro/graph/layers/wms/DescribeLayer" \
  -H "Authorization: YOUR_API_KEY" \
  --data-urlencode "service=WMS" \
  --data-urlencode "version=1.1.1" \
  --data-urlencode "request=DescribeLayer" \
  --data-urlencode "layers=GRAPHRASTER:light_pollution"

GetMap

Render a map tile (PNG image) for a given area, layers, and style.

Purpose: Generate styled map images for display on web maps or in applications.

Required Parameters

Parameter	Description	Example
`service`	`WMS`	`WMS`
`version`	`1.3.0`	`1.3.0`
`request`	`GetMap`	`GetMap`
`layers`	Comma-separated layer names	`GRAPHRASTER:light_pollution`
`styles`	Comma-separated style names (or empty for defaults)	`` (empty) or `light_style`
`srs` / `crs`	Spatial Reference System (EPSG code)	`EPSG:3857` (Web Mercator)
`bbox`	Bounding box: `minx,miny,maxx,maxy` in SRS units	`975947.9771,6657970.9118,1533632.5355,7037098.5720`
`width`	Width of output in pixels	`256`
`height`	Height of output in pixels	`256`
`format`	Output format	`image/png`

Optional Parameters

Parameter	Description	Example
`transparent`	Whether background is transparent	`true`
`bgcolor`	Background color in RRGGBB hex format	`FFFFFF`
`exceptions`	Exception format	`application/json`
`time`	Time value for temporal layers	`2023-01-01T00:00:00Z`
`sld`	URL to external SLD document	`https://example.com/style.sld`
`sld_body`	URL-encoded SLD XML	(see examples)

Example: Basic 256×256 Tile

cURL
JavaScript
Python

curl -X GET "https://graph.quarticle.ro/graph/layers/wms/GetMap" \
  -H "Authorization: YOUR_API_KEY" \
  --data-urlencode "service=WMS" \
  --data-urlencode "version=1.3.0" \
  --data-urlencode "request=GetMap" \
  --data-urlencode "layers=GRAPHRASTER:light_pollution" \
  --data-urlencode "styles=" \
  --data-urlencode "srs=EPSG:3857" \
  --data-urlencode "bbox=975947.9771,6657970.9118,1533632.5355,7037098.5720" \
  --data-urlencode "width=256" \
  --data-urlencode "height=256" \
  --data-urlencode "format=image/png" \
  --data-urlencode "transparent=true" \
  -o tile.png

const apiKey = process.env.QARTA_API_KEY;

const params = new URLSearchParams({
  service: 'WMS',
  version: '1.3.0',
  request: 'GetMap',
  layers: 'GRAPHRASTER:light_pollution',
  styles: '',
  srs: 'EPSG:3857',
  bbox: '975947.9771,6657970.9118,1533632.5355,7037098.5720',
  width: '256',
  height: '256',
  format: 'image/png',
  transparent: 'true'
});

const url = `https://graph.quarticle.ro/graph/layers/wms/GetMap?${params}`;
const imgElement = document.querySelector('img');
imgElement.src = url;
imgElement.onload = () => console.log('Tile loaded');

import requests

api_key = os.getenv('QARTA_API_KEY')

response = requests.get(
  'https://graph.quarticle.ro/graph/layers/wms/GetMap',
  params={
    'service': 'WMS',
    'version': '1.3.0',
    'request': 'GetMap',
    'layers': 'GRAPHRASTER:light_pollution',
    'styles': '',
    'srs': 'EPSG:3857',
    'bbox': '975947.9771,6657970.9118,1533632.5355,7037098.5720',
    'width': '256',
    'height': '256',
    'format': 'image/png',
    'transparent': 'true'
  },
  headers={'Authorization': f'{api_key}'}
)

with open('tile.png', 'wb') as f:
  f.write(response.content)

Tips

EPSG:3857: Use for web map tiles (Web Mercator projection)
EPSG:4326: Use for reprojected data (lat/lon, rarely for tiles)
SRS vs CRS: WMS 1.1.x uses srs, WMS 1.3.0 uses crs (GeoServer accepts both)
format=image/png: Produces smaller, 8-bit PNG tiles
transparent=true: Allows background to show through (useful for overlays)
Multiple layers: Separate with commas: layers=layer1,layer2,layer3

GetFeatureInfo

Query feature attributes at a pixel location on a rendered map.

Purpose: "Click to query" — get attribute values from a location on a map.

Required Parameters

All GetMap parameters, plus:

Parameter	Description	Example
`query_layers`	Layers to query (subset of `layers`)	`GRAPHRASTER:light_pollution`
`x`	X coordinate of query point (in pixels)	`5`
`y`	Y coordinate of query point (in pixels)	`5`

Optional Parameters

Parameter	Description
`info_format`	Response format: `text/html`, `application/json`, `text/plain`
`feature_count`	Max features to return. Default: `1`

Example

cURL

curl -X GET "https://graph.quarticle.ro/graph/layers/wms/GetFeatureInfo" \
  -H "Authorization: YOUR_API_KEY" \
  --data-urlencode "service=WMS" \
  --data-urlencode "version=1.3.0" \
  --data-urlencode "request=GetFeatureInfo" \
  --data-urlencode "layers=GRAPHRASTER:light_pollution" \
  --data-urlencode "query_layers=GRAPHRASTER:light_pollution" \
  --data-urlencode "styles=" \
  --data-urlencode "srs=EPSG:3857" \
  --data-urlencode "bbox=975947.9771,6657970.9118,1533632.5355,7037098.5720" \
  --data-urlencode "width=256" \
  --data-urlencode "height=256" \
  --data-urlencode "x=128" \
  --data-urlencode "y=128" \
  --data-urlencode "info_format=application/json"

GetLegendGraphic

Retrieve a rendered legend image for a layer and style.

Purpose: Display layer legend in your application.

Required Parameters

Parameter	Description	Example
`service`	`WMS`	`WMS`
`version`	`1.0.0`	`1.0.0`
`request`	`GetLegendGraphic`	`GetLegendGraphic`
`layer`	Layer name	`GRAPHRASTER:light_pollution`
`styles`	Style name	`light_style` or empty
`format`	Image format	`image/png`

Optional Parameters

Parameter	Description
`width`	Width in pixels (default: 20)
`height`	Height in pixels (default: 20)
`rule`	Specific rule from style (if applicable)
`scale`	Standardized scale denominator
`sld`	URL to external SLD document
`sld_body`	URL-encoded SLD XML
`language`	Language for labels

Example

cURL

curl -X GET "https://graph.quarticle.ro/graph/layers/wms/GetLegendGraphic" \
  -H "Authorization: YOUR_API_KEY" \
  --data-urlencode "service=WMS" \
  --data-urlencode "version=1.0.0" \
  --data-urlencode "request=GetLegendGraphic" \
  --data-urlencode "layer=GRAPHRASTER:light_pollution" \
  --data-urlencode "format=image/png" \
  --data-urlencode "width=40" \
  --data-urlencode "height=40" \
  -o legend.png

Error Handling

If a GetMap or GetCapabilities request fails, the error is returned in the requested exception format:

<?xml version="1.0" encoding="UTF-8"?>
<ServiceExceptionReport version="1.3.0">
  <ServiceException>
    Layer 'invalid_layer' not found
  </ServiceException>
</ServiceExceptionReport>

Or as JSON if exceptions=application/json:

{
  "code": "InvalidLayer",
  "message": "Layer 'invalid_layer' not found"
}

Common errors:

InvalidLayer: Layer name doesn't exist. Check GetCapabilities.
InvalidSRS: SRS/CRS code not supported. Typical: EPSG:3857, EPSG:4326.
InvalidBBox: Bounding box format incorrect or out of range.
Unauthorized: API key is missing or invalid.

Next Steps

GeoServer Overview
WFS Guide — Query raw feature data
Map Visualization Use Case — Embed WMS in web maps

GetCapabilities​

Required Parameters​

Response​

DescribeLayer​

Required Parameters​

Optional Parameters​

Example​

GetMap​

Required Parameters​

Optional Parameters​

Example: Basic 256×256 Tile​

Tips​

GetFeatureInfo​

Required Parameters​

Optional Parameters​

Example​

GetLegendGraphic​

Required Parameters​

Optional Parameters​

Example​

Error Handling​

Next Steps​

GetCapabilities

Required Parameters

Response

DescribeLayer

Required Parameters

Optional Parameters

Example

GetMap

Required Parameters

Optional Parameters

Example: Basic 256×256 Tile

Tips

GetFeatureInfo

Required Parameters

Optional Parameters

Example

GetLegendGraphic

Required Parameters

Optional Parameters

Example

Error Handling

Next Steps