Web Mapping Tools

Examples for accessing USGS Astrogeology WMS services with GDAL, OpenLayers, and Leaflet

Overview

The USGS Astrogeology Science Center provides Web Map Service (WMS) endpoints for planetary data. This guide demonstrates how to access these services using GDAL configuration files and web mapping libraries.

GDAL WMS Configuration

Overview

GDAL can retrieve images from WMS layers using XML configuration files, enabling command-line access to planetary base maps and elevation data.

Basic Usage

gdal_translate -of PNG gdal_MDIM21.xml mdim21_out.png

This command retrieves data from a WMS layer and exports it as a PNG image.

WMS Configuration Files

Mars MDIM 2.1 Mosaic

Access the Mars Digital Image Mosaic (MDIM 2.1):

<GDAL_WMS>
  <Service name="WMS">
    <Version>1.1.1</Version>
    <ServerUrl>http://planetarymaps.usgs.gov/cgi-bin/mapserv?map=/maps/mars/mars_simp_cyl.map</ServerUrl>
    <SRS>EPSG:4326</SRS>
    <ImageFormat>image/jpeg</ImageFormat>
    <Layers>MDIM21</Layers>
  </Service>
  <DataWindow>
    <UpperLeftX>280</UpperLeftX>
    <UpperLeftY>45</UpperLeftY>
    <LowerRightX>290</LowerRightX>
    <LowerRightY>35</LowerRightY>
    <SizeX>1000</SizeX>
    <SizeY>1000</SizeY>
  </DataWindow>
  <Projection>EPSG:4326</Projection>
  <BandsCount>3</BandsCount>
  <DataType>Byte</DataType>
</GDAL_WMS>

Key Parameters:

• ServerUrl: WMS endpoint URL
• Layers: Layer name (MDIM21)
• ImageFormat: image/jpeg for RGB imagery
• BandsCount: 3 (RGB)
• DataType: Byte (8-bit)

Mars MOLA Elevation

Access Mars Orbiter Laser Altimeter (MOLA) elevation data:

<GDAL_WMS>
  <Service name="WMS">
    <Version>1.1.1</Version>
    <ServerUrl>http://wms.wr.usgs.gov/cgi-bin/mapserv?map=/maps/mars/mars_simp_cyl_elev.map</ServerUrl>
    <SRS>EPSG:4326</SRS>
    <ImageFormat>image/tiff</ImageFormat>
    <Layers>MOLA_elev</Layers>
  </Service>
  <DataWindow>
    <UpperLeftX>280</UpperLeftX>
    <UpperLeftY>45</UpperLeftY>
    <LowerRightX>290</LowerRightX>
    <LowerRightY>35</LowerRightY>
    <SizeX>1000</SizeX>
    <SizeY>1000</SizeY>
  </DataWindow>
  <Projection>EPSG:4326</Projection>
  <BandsCount>1</BandsCount>
  <DataType>Int16</DataType>
</GDAL_WMS>

Key Parameters:

• ImageFormat: image/tiff for elevation data
• BandsCount: 1 (elevation only)
• DataType: Int16 (16-bit signed integer)

Moon LOLA Elevation

Access Lunar Orbiter Laser Altimeter (LOLA) elevation data:

<GDAL_WMS>
  <Service name="WMS">
    <Version>1.1.1</Version>
    <ServerUrl>http://wms.wr.usgs.gov/cgi-bin/mapserv?map=/maps/earth/moon_simp_cyl_elev.map</ServerUrl>
    <SRS>EPSG:4326</SRS>
    <ImageFormat>image/tiff</ImageFormat>
    <Layers>LOLA_elev</Layers>
  </Service>
  <DataWindow>
    <UpperLeftX>175</UpperLeftX>
    <UpperLeftY>45</UpperLeftY>
    <LowerRightX>185</LowerRightX>
    <LowerRightY>35</LowerRightY>
    <SizeX>1000</SizeX>
    <SizeY>1000</SizeY>
  </DataWindow>
  <Projection>EPSG:4326</Projection>
  <BandsCount>1</BandsCount>
  <DataType>Int16</DataType>
</GDAL_WMS>

GDAL WMS Usage Examples

Export Specific Region

Create a configuration file with your desired extent:

<DataWindow>
  <UpperLeftX>-180</UpperLeftX>   <!-- West longitude -->
  <UpperLeftY>90</UpperLeftY>      <!-- North latitude -->
  <LowerRightX>180</LowerRightX>   <!-- East longitude -->
  <LowerRightY>-90</LowerRightY>   <!-- South latitude -->
  <SizeX>3600</SizeX>              <!-- Output width in pixels -->
  <SizeY>1800</SizeY>              <!-- Output height in pixels -->
</DataWindow>

Then export:

gdal_translate -of GTiff mars_config.xml mars_region.tif

Get Dataset Information

gdalinfo gdal_mars_MOLA_elev.xml

Output shows:

• Coordinate system
• Pixel size
• Bounding box
• Data type
• Band information

Reproject WMS Data

gdalwarp -t_srs "+proj=sinu +lon_0=0 +x_0=0 +y_0=0 +R=3396190 +units=m" \
  gdal_mars_MOLA_elev.xml mars_sinusoidal.tif

Create Hillshade from Elevation WMS

# Download elevation data
gdal_translate -of GTiff gdal_mars_MOLA_elev.xml mars_elev.tif

# Generate hillshade
gdaldem hillshade mars_elev.tif mars_hillshade.tif -z 5 -az 315 -alt 45

OpenLayers Example

Interactive Moon Map

HTML template for displaying lunar WMS layers with OpenLayers:

<!DOCTYPE html>
<html>
<head>
  <link rel="stylesheet" href="http://astrowebmaps.wr.usgs.gov/webmapatlas/styles/ol.css" />
  <script src="http://astrowebmaps.wr.usgs.gov/webmapatlas/ol/OpenLayers-2.10/OpenLayers.js"></script>
  <style>
    #map { width: 100%; height: 100%; border: 1px solid black; }
  </style>
</head>
<body>
  <div id='map'></div>
  <script type="text/javascript">
    var map = new OpenLayers.Map('map', { 
      maxExtent: new OpenLayers.Bounds(0, -90, 360, 90) 
    });
    
    var wmsURL = [
      "http://planetarymaps.usgs.gov/cgi-bin/mapserv?map=/maps/earth/moon_simp_cyl.map"
    ];

    // Add LOLA Color layer
    var LOLA_color = new OpenLayers.Layer.WMS(
      'LOLA Color',
      wmsURL,
      { layers: 'LOLA_color', format: 'image/jpeg' },
      { wrapDateLine: true, buffer: 1, isBaseLayer: true, visibility: true }
    );
    map.addLayer(LOLA_color);

    // Add LOLA Steel layer
    var LOLA_steel = new OpenLayers.Layer.WMS(
      'LOLA Steel',
      wmsURL,
      { layers: 'LOLA_steel', format: 'image/jpeg' },
      { wrapDateLine: true, buffer: 1, isBaseLayer: true, visibility: false }
    );
    map.addLayer(LOLA_steel);

    // Add LOLA Black & White layer
    var LOLA_bw = new OpenLayers.Layer.WMS(
      'LOLA B&W',
      wmsURL,
      { layers: 'LOLA_bw', format: 'image/jpeg' },
      { wrapDateLine: true, buffer: 1, isBaseLayer: true, visibility: false }
    );
    map.addLayer(LOLA_bw);

    // Set initial view
    map.setCenter(new OpenLayers.LonLat(90, -35), 7);
    
    // Add controls
    map.addControl(new OpenLayers.Control.MousePosition());
    map.addControl(new OpenLayers.Control.PanZoomBar());
    map.addControl(new OpenLayers.Control.LayerSwitcher({'ascending':true}));
    map.addControl(new OpenLayers.Control.ScaleLine());
    map.addControl(new OpenLayers.Control.Graticule());
  </script>
</body>
</html>

Available Lunar Layers

LOLA_color

Color-coded elevation visualization

LOLA_steel

Grayscale elevation (steel colormap)

LOLA_bw

Black and white shaded relief

LROC_WAC

Wide Angle Camera mosaic

UVVIS

Clementine UVVIS mosaic

KaguyaTC_Ortho

JAXA Kaguya Terrain Camera

LO

Lunar Orbiter mosaic

Leaflet Example

Modern Lunar Web Map

Lightweight alternative using Leaflet:

<!DOCTYPE html>
<html>
<head>
  <title>WMS Example - Leaflet</title>
  <meta charset="utf-8" />
  <link rel="stylesheet" href="https://unpkg.com/leaflet@1.0.3/dist/leaflet.css" />
  <script src="https://unpkg.com/leaflet@1.0.3/dist/leaflet.js"></script>
  <style>
    #map { width: 600px; height: 400px; }
  </style>
</head>
<body>
  <div id='map'></div>
  <script type="text/javascript">
    // Define WMS layers
    var LROC_WAC = L.tileLayer.wms(
      'https://planetarymaps.usgs.gov/cgi-bin/mapserv?map=/maps/earth/moon_simp_cyl.map',
      { layers: 'LROC_WAC' }
    );
    
    var LOLA_color = L.tileLayer.wms(
      'https://planetarymaps.usgs.gov/cgi-bin/mapserv?map=/maps/earth/moon_simp_cyl.map',
      { layers: 'LOLA_color' }
    );

    // Initialize map
    var map = L.map('map', {
      crs: L.CRS.EPSG4326,
      center: [0, 0],
      zoom: 1,
      layers: [LROC_WAC, LOLA_color]
    });

    // Add layer control
    var baseMaps = {
      "LROC_WAC": LROC_WAC,
      "LOLA_color": LOLA_color
    };
    
    L.control.layers(baseMaps).addTo(map);
  </script>
</body>
</html>

Adding GeoJSON Overlay

Include region of interest as GeoJSON:

// Define GeoJSON polygon
var pubextent = {
  "type": "FeatureCollection",
  "properties": {"title": "Example polygon"},
  "features": [{
    "type": "Feature",
    "properties": {},
    "geometry": {
      "type": "Polygon",
      "coordinates": [
        [[50, 22.5], [50, 27.5], [60, 27.5], [60, 22.5], [50, 22.5]]
      ]
    }
  }]
};

// Add to map
L.geoJson(pubextent).addTo(map);

Custom Styling for GeoJSON

L.geoJson(pubextent, {
  style: {
    color: '#ff0000',
    weight: 2,
    opacity: 0.8,
    fillColor: '#ff0000',
    fillOpacity: 0.2
  },
  onEachFeature: function (feature, layer) {
    if (feature.properties.title) {
      layer.bindPopup(feature.properties.title);
    }
  }
}).addTo(map);

Available WMS Endpoints

USGS Astrogeology WMS Services

Moon

Base URL: http://planetarymaps.usgs.gov/cgi-bin/mapserv?map=/maps/earth/moon_simp_cyl.map

Available Layers:

• LOLA_color - LOLA elevation (color)
• LOLA_steel - LOLA elevation (steel)
• LOLA_bw - LOLA elevation (grayscale)
• LROC_WAC - LROC Wide Angle Camera
• uv_v2 - Clementine UVVIS v2
• KaguyaTC_Ortho - Kaguya Terrain Camera
• LO - Lunar Orbiter

Elevation URL: http://wms.wr.usgs.gov/cgi-bin/mapserv?map=/maps/earth/moon_simp_cyl_elev.map

• LOLA_elev - LOLA elevation (Int16)

Mars

Base URL: http://planetarymaps.usgs.gov/cgi-bin/mapserv?map=/maps/mars/mars_simp_cyl.map

Available Layers:

• MDIM21 - Mars Digital Image Mosaic 2.1
• THEMIS_IR_Day - THEMIS Infrared Day
• THEMIS_IR_Night - THEMIS Infrared Night
• Viking_MDIM21 - Viking MDIM 2.1

Elevation URL: http://wms.wr.usgs.gov/cgi-bin/mapserv?map=/maps/mars/mars_simp_cyl_elev.map

• MOLA_elev - MOLA elevation (Int16)

For a complete list of available layers, visit the USGS Astro Web Map Atlas

GetCapabilities Requests

Query Available Layers

Get WMS capabilities to discover all available layers:

curl "http://planetarymaps.usgs.gov/cgi-bin/mapserv?map=/maps/earth/moon_simp_cyl.map&SERVICE=WMS&REQUEST=GetCapabilities"

This returns an XML document listing:

• Available layers
• Supported formats
• Coordinate systems
• Bounding boxes
• Layer metadata

Parse Capabilities with Python

from owslib.wms import WebMapService

wms = WebMapService('http://planetarymaps.usgs.gov/cgi-bin/mapserv?map=/maps/earth/moon_simp_cyl.map')

print(f"Title: {wms.identification.title}")
print(f"Layers: {list(wms.contents)}")

# Get layer details
for layer in wms.contents:
    print(f"\nLayer: {layer}")
    print(f"  Title: {wms[layer].title}")
    print(f"  BoundingBox: {wms[layer].boundingBox}")

Advanced Techniques

Transparent Overlays

Combine base imagery with transparent overlays:

// Leaflet example
var baseLayer = L.tileLayer.wms(wmsUrl, {
  layers: 'LROC_WAC',
  format: 'image/jpeg'
});

var overlayLayer = L.tileLayer.wms(wmsUrl, {
  layers: 'nomenclature',
  format: 'image/png',
  transparent: true
});

map.addLayer(baseLayer);
map.addLayer(overlayLayer);

Time Series Animation

For temporal datasets with time parameter support:

var timeLayer = L.tileLayer.wms(wmsUrl, {
  layers: 'seasonal_data',
  time: '2023-01-01',
  format: 'image/png'
});

// Update time parameter
function updateTime(newTime) {
  timeLayer.setParams({ time: newTime });
}

GetFeatureInfo Requests

Query pixel values from WMS layers:

map.on('click', function(e) {
  var url = LOLA_color.getFeatureInfoUrl(e.latlng, {
    query_layers: 'LOLA_elev',
    info_format: 'text/plain'
  });
  
  fetch(url)
    .then(response => response.text())
    .then(data => console.log('Elevation:', data));
});

Performance Optimization

Tile Caching

For repeated access, consider setting up a local tile cache using MapProxy or TileCache to reduce server load and improve performance.

MapProxy Configuration Example:

sources:
  moon_wms:
    type: wms
    req:
      url: http://planetarymaps.usgs.gov/cgi-bin/mapserv?map=/maps/earth/moon_simp_cyl.map
      layers: LOLA_color

layers:
  - name: moon_cached
    title: Cached Moon Layer
    sources: [moon_wms]

caches:
  moon_cache:
    grids: [EPSG4326]
    sources: [moon_wms]

Request Optimization

// Use appropriate tile size
var layer = L.tileLayer.wms(url, {
  layers: 'LOLA_color',
  tileSize: 512,  // Reduce number of requests
  maxZoom: 10      // Prevent excessive detail requests
});

Troubleshooting

Common Issues

Issue: “Service not found” error
Solution: Verify the map file path in ServerUrl is correct

Issue: Blank tiles or no data
Solution: Check DataWindow coordinates are within valid range (Lon: -180 to 360, Lat: -90 to 90)

Issue: Slow performance
Solution: Reduce SizeX/SizeY values, use appropriate image format (JPEG for imagery, TIFF for elevation)

Issue: Coordinate system mismatch
Solution: Ensure EPSG:4326 is specified in both Service/SRS and Projection elements

Source Files Reference

• gdal_MDIM21.xml - Mars MDIM 2.1 configuration
• gdal_mars_MOLA_elev.xml - Mars MOLA elevation configuration
• gdal_moon_LOLA_elev.xml - Moon LOLA elevation configuration
• OpenLayers_MyMoon.html - OpenLayers implementation example
• leaflet_moonWMS2_wGeoJSON_Box.html - Leaflet implementation example

Additional Resources

USGS Astro Web Maps

Complete layer catalog and documentation

GDAL WMS Driver

GDAL WMS driver documentation

OpenLayers API

OpenLayers documentation and examples

Leaflet Documentation

Leaflet API reference and tutorials

See Also

• OGC WMS Specification
• GDAL Virtual File Systems
• IAU Planetary Projections