graph LR
A[GIBS API] --> B[STAC Collection]
B --> C[VEDA Catalog]
subgraph VedaIntegration [VEDA Integration]
D[Dashboard Visualization]
E[API Access]
F[Data Discovery]
style VedaIntegration fill:#D3D3D3
end
C --> D
C --> E
C --> F
Global Imagery Browse Services (GIBS) Integration
Indexing OGC Web Map Tile Services for STAC collection creation
Global Imagery Browse Services (GIBS) delivers access to full-resolution visualizations of satellite imagery through standardized access through services like the OGC Web Map Tile Service or Wep Map Service.
OGC Web Map Tile Service (WMTS) A WMTS enabled server application can serve map tiles of spatially referenced data using tile images with predefined content, extent, and resolution.
OGC Web Map Service (WMS) Provides a simple HTTP interface for requesting geo-registered map images from one or more distributed geospatial databases.
Overview
NASA’s Global Imagery Browse Services (GIBS) API leverages the OGC WMTS specification to deliver the collections of NASA satellite imagery.
Web Map Tile Service (WMTS) is used for interactive web mapping and is an OGC standard for serving pre-rendered map tiles by pre-generating and caching tiles on the server. To learn more about the OGC WMTS implementation of a STAC compliant collection, please refer to the web-map-links extension documentation.
Architecture
STAC Collection with GIBS Web Map Links Example
The GEDI_ISS_L3_Canopy_Height_Mean_RH100_201904-202303 collection is an example of a STAC compliant collection that implements the web map links extension for a GIBS hosted dataset.
This stac-browser preview https://radiantearth.github.io/stac-browser/#/external/staging.openveda.cloud/api/stac/collections/GEDI_ISS_L3_Canopy_Height_Mean_RH100_201904-202303 for the collection mentioned above shows how the web map links supports dynamic visualization of the data utilizing pre-rendered map tiles.
To integrate WMTS capabilities into a STAC collection, you need to implement the web map links extension.
Implementing Web Map Link Extensions for GIBS hosted datasets
In this section, we will explain what is needed to create a web map link metadata for a GIBS hosted dataset in order to render WMTS map layers.
Key Configuration Elements
This section outlines the key fields that are added to make a Web Map Links object in a VEDA STAC collection to describe how to visualize a dataset using GIBS’s Web Map Tilling Service.
The rel field is required and indicates the type of web map link. For example wms for a Web Map Service or wmts for a Web Map Tile Service. In this case, we would use wmts. But the full list of valid rel field values and additional metadata for that specific extension type can be found in the web-map-links docs.
The href field is also required and indicates the URL of the web map link. In this case, the value would be "https://gibs.earthdata.nasa.gov/wmts/epsg3857/best/wmts.cgi".
Tip
For reference, this OGC WMTS Web Map Links Extension Table within the stac-extensions/web-map-links documentation details the required and optional fields for the WMTS extension to be STAC compliant.
Creation
To create this Web Map Link Extension, define an object with "rel": "wmts" and "href": "https://gibs.earthdata.nasa.gov/wmts/epsg3857/best/wmts.cgi" and then add any additional metadata.
The extension object would look like this:
{
"rel": "wmts",
"href": "https://gibs.earthdata.nasa.gov/wmts/epsg3857/best/wmts.cgi", // Required: Link to the WMTS wihtout any specific query parameters
"type": "image/png", // Media type to be used for the tile requests
"title": "Visualized through a WMTS",
"wmts:layer": [
"GEDI_ISS_L3_Canopy_Height_Mean_RH100_201904-202303" // Required: specific layers to show on map by default. Can be a list of layer names or a single layer name
],
"href:servers": [ // Specifies a set of URLs for a web mapping library so requests can be sent to multiple servers to avoid request limits
"https://gibs-a.earthdata.nasa.gov/wmts/epsg3857/best/wmts.cgi",
"https://gibs-b.earthdata.nasa.gov/wmts/epsg3857/best/wmts.cgi"
],
"wmts:dimensions": { // Any additional dimension parameters
"STYLE": "default"
}
}With this extension, you would add it to your STAC compliant collection object within the links array.
Closer Look at GIBS API WMTS Capabilities
Information about GIBS dataset can be found in GIB’s Available Visualizations documentation. Details can also be found within the XML document response of a WMTS GetCapabilities request as documented below.
# Construct WMTS capability URL.
wmtsUrl = 'http://gibs.earthdata.nasa.gov/wmts/epsg4326/best/wmts.cgi?SERVICE=WMTS&REQUEST=GetCapabilities'
# Request capabilities.
response = requests.get(wmtsUrl)
# Display capability XML.
WmtsXml = xmltree.fromstring(response.content)
# Uncomment the following to display the large file:
# print(xmltree.tostring(WmtsXml, pretty_print = True, encoding = str))This will return the WMTS capabilities document in XML format for all NASA GIBS hosted dataset layers.
To return a single layer’s capabilities, you would have to parse the XML response. Below is an example of a bash script to filter the GetCapabilities response for a specific layer, GEDI_ISS_L3_Canopy_Height_Mean_RH100_201904-202303.
curl 'https://gibs.earthdata.nasa.gov/wmts/epsg3857/best/wmts.cgi?service=wmts&request=GetCapabilities' | xq '.Capabilities.Contents.Layer[] | select( .["ows:Identifier"] | contains("GEDI_ISS_L3_Canopy_Height_Mean_RH100_201904-202303"))'// response
"ows:Title": {
"@xml:lang": "en",
"#text": "Canopy Height Mean (L3, RH100, 201904-202303, GEDI, ISS)"
},
"ows:WGS84BoundingBox": {
"@crs": "urn:ogc:def:crs:OGC:2:84",
"ows:LowerCorner": "-180 -85.051129",
"ows:UpperCorner": "180 85.051129"
},
"Style": {
"@isDefault": "true",
"ows:Title": {
"@xml:lang": "en",
"#text": "default"
},
"ows:Identifier": "default",
"LegendURL": [
{
"@xlink:title": "GIBS Color Map Legend: Horizontal",
"@xlink:href": "https://gibs.earthdata.nasa.gov/legends/GEDI_RH100_Mean_Color_Index_H.svg",
"@xlink:role": "http://earthdata.nasa.gov/gibs/legend-type/horizontal",
"@height": "86",
"@format": "image/svg+xml",
"@width": "378",
"@xlink:type": "simple"
},
{
"@xlink:title": "GIBS Color Map Legend: Vertical",
"@xlink:href": "https://gibs.earthdata.nasa.gov/legends/GEDI_RH100_Mean_Color_Index_V.svg",
"@xlink:role": "http://earthdata.nasa.gov/gibs/legend-type/vertical",
"@height": "288",
"@format": "image/svg+xml",
"@width": "135",
"@xlink:type": "simple"
}
]
},
"Dimension": {
"ows:Identifier": "Time",
"ows:UOM": "ISO8601",
"Default": "2019-04-18",
"Current": "false",
"Value": "2019-04-18/2019-04-18/P1429D"
},
"TileMatrixSetLink": {
"TileMatrixSet": "GoogleMapsCompatible_Level7"
},In this response, there is useful info for populating STAC metadata and to inform visualization expectations – note the "TileMatrixSet": "GoogleMapsCompatible_Level7" tells us that tiles are only provided up to zoom level 7. At higher zooms, the tiles will become blurry.