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Stac Collection File Documentation

Last Updated: June 15, 2022

Overview

The Select STAC Collection file lists details about the image tiles selected in the cell. This file is created as part of the results of an imagery selection request to the "Select API". To access the STAC file, make a "GET Status" request to the Select API. In the links section, the file is listed as:

   "stac": "https://ard.maxar.com/api/v1/select/files/{select_id}.stac"

The STAC file is a GeoJSON feature collection. There are two object types within the feature collection:

Type Description
Collection Information about the collection of ARD tiles in a grid cell.
Feature The metadata for a specific tile in the collection.

Feature Collection contents

Collection

A Collection object provides information about the tile collection in the grid cell.

Field Type Description Example
type string The type of the GeoJSON object. The type for this file is FeatureCollection. "type": "Collection"
stac_version string The STAC version used for the collection file. "stac_version": "1.0.0"
stac_extensions string There are no STAC extensions used in the Select STAC collection file. "stac_extensions": []
id string The unique identifier for a cell is {utm-zone}-{quadkey}. "id":"Z13-031133320302"
title string A title for the collection. "title": "ARD tiles in grid cell "Z13-031133320302"
description string A description for the collection. "description": "ARD tiles in grid cell "Z13-031133320302"
license string The type of license for the associated image within the requested cells. "license": "proprietary"
providers string The provider of the data. "providers": [{"name": "Maxar"}]
extent object Spatial and temporal extents for the collection. See Extent Table
links object A list of links to resources and additional URLs See Links Table
assets object In Collection objects, the "asset" value is empty. "assets": {}

Feature

A Feature object includes the metadata for a specific tile within the collection.

Field Type Description Example
type string The type of the GeoJSON object. "type": "Feature"
geometry GeoJSON geometry object The geometry coordinates for the tile. See example file
properties object Additional metadata for the item. See Properties Table
stac_version string The STAC version used for the collection file. "stac_version": "1.0.0"
stac_extensions string The Feature object uses the "eo" and "view" STAC extensions. "stac_extensions": ["https://stac-extensions.github.io/eo/v1.0.0/schema.json", "https://stac-extensions.github.io/view/v1.0.0/schema.json"]
bbox string The bounding box coordinates for the tile. "bbox": [-106.7616552633806, 35.36549648670249, -106.758117259609, 35.38791075120405]
links object A list of links to resources and additional URLs See [Links Table](#links Table](#links-object)

Extent object

The "extent" object lists the spatial and temporal extents for the collection of items.

Extent Field Description Example
spatial bbox Extents of the grid tile. "bbox":[[-106.70615363267751, 35.321221334585616, -106.65022020809855, 35.36705036939606]]
temporal interval Date interval extents of the selection. "interval": [["2021-09-21 18:34:57Z", "2021-09-21 18:34:59Z"]]

The links object provides URLs to metadata files and shows their relationship to the file.

Field Description Example
rel The relationship between the link and the entity it describes. See "relationship" table below. "rel": "self"
href The URL for the linked file. "href": "https://ard.maxar.com/api/v1/metadata/cells/"Z13-031133320302/acquisitions?format=stac"

Relationship types

Relationship Object Description Example
self Collection and Feature The URL for the current file "href": "https://ard.maxar.com/api/v1/metadata/cells/Z13-031133320302/acquisitions?format=stac"
request_details Collection The URL for the Select Request file. "href": "https://ard.maxar.com/api/v1/select/request/5934867769455521373"
collection Collection and Feature The URL for the Collection href": "https://ard.maxar.com/api/v1/metadata/cells/Z13-031133320302/acquisitions?format=stac"

Properties object

The properties object lists additional metadata for the item. When a property is prepended by a {name}:, this indicates the STAC extension the property is derived from.

Field Type Description Example
datetime string an ISO-8601-formatted string to indicate the imagery date; to indicate a range use a / to separate two date strings, e.g. “2019-10-25T09:00:00Z/2020-10-26T13:00:00Z”; for open-ended ranges use .. as the date e.g. "2019-10-25T09:00:00Z/.. "datetime": "2021-09-21 18:34:57Z"
platform string The satellite that acquired the image. "platform": "WV03"
gsd number The spatial resolution, or ground sampling distance, of the sensor that acquired the image, stated in meters. "gsd": 0.32
ard_metadata_version string The version number assigned to ARD metadata. "ard_metadata_version": "0.0.1"
catalog_id string The unique identifier for the item, as assigned by the provider, Maxar. This is also referred to as the "acquisition ID". "catalog_id": "104001006D0BB300"0
utm_zone number The Universal Transverse Mercator(UTM) coordinate system number assigned to the zone where the item is located. "utm_zone": 11
proj:epsg integer The coordinate reference system used by the asset data. Maxar ARD uses "epsg". "proj:epsg": 32611
proj: geometry GeoJSON geometry object Defines the footprint of this Item in native UTM projection. see example below this table.
proj:bbox number Bounding box of the Item in the asset coordinate reference system (CRS), in 2 or 3 dimensions; native UTM projection. see example below this table.
quadkey string The address where the item is located on the Maxar grid. "quadkey": "031311311232"
tile:data_area number The square kilometer area of the tile with data. "tile:data_area": 12.8
tile:clouds_area number The square kilometer area of the tile that has clouds. "tile:clouds_area": 0
tile:clouds_percent number The percentage of the tile that is covered by clouds. "tile:clouds_percent": 0
view:off_nadir number The angle from the sensor between nadir (straight down) and the scene center. Measured in degrees (0-90). "view:off_nadir": 13.0
view:azimuth number Sun azimuth angle. From the scene center point on the ground, this is the angle between true north and the sun. Measured clockwise in degrees (0-360). "view:azimuth": 153.5
view:incidence_angle number The incidence angle is the angle between the vertical (normal) to the intercepting surface and the line of sight back to the satellite at the scene center. Measured in degrees (0-90). "view:incidence_angle": 74.7
view:sun_azimuth number Sun azimuth angle. From the scene center point on the ground, this is the angle between truth north and the sun. Measured clockwise in degrees (0-360). "view:sun_azimuth": 150.7
view:sun_elevation number Sun elevation angle. The angle from the tangent of the scene center point to the sun. Measured from the horizon in degrees (-90-90). Maxar ARD is not available with a sun elevation of less than 5 degrees (nighttime imagery). "view:sun_elevation": 54.1

Assets

Field Description Example
preview The name of the asset. "preview"
title The title of the asset. "title": "Preview of 10300100B3841C00 in grid cell Z13-031133320302"
type The type of asset. "type": "image/jpeg"
role The role assigned to the asset. "roles": ["thumbnail"]
href The URL for the asset. This URL can be accessed from your browser. "href": "https://ard.maxar.com/api/v1/browse/preview/10300100B3841C00/Z13-031133320302"
id The ID for the tile is {cell ID}/{acquisition ID}. "id": "Z13-031133320302/10300100B3841C00"

Example STAC Collection File

This example includes one Collection object and one Feature object.

{
    "type": "FeatureCollection",
    "collections": [{
        "type": "Collection",
        "stac_version": "1.0.0",
        "stac_extensions": [],
        "id": "Z13-031133320302",
        "title": "ARD tiles in grid cell Z13-031133320302",
        "description": "ARD tiles in grid cell Z13-031133320302",
        "license": "proprietary",
        "providers": [{
            "name": "Maxar"
        }],
        "extent": {
            "spatial": {
                "bbox": [[-106.70615363267751, 35.321221334585616, -106.65022020809855, 35.36705036939606]]
            },
            "temporal": {
                "interval": [
                    [null, null]
                ]
            }
        },
        "links": [{
            "rel": "self",
            "href": "https://ard.maxar.com/api/v1/metadata/cells/Z13-031133320302/acquisitions?format=stac"
        }, {
            "rel": "request_details",
            "href": "https://ard.maxar.com/api/v1/select/request/5934867769455521373"
        }],
        "assets": {}
    }],
    "features": [{
        "type": "Feature",
        "geometry": {
            "type": "Polygon",
            "coordinates": [
                [
                    [-106.758117259609, 35.36554092138188],
                    [-106.761168016614, 35.36549648670249],
                    [-106.7616552633806, 35.38791075120405],
                    [-106.758124, 35.387909],
                    [-106.758123, 35.387058],
                    [-106.758117259609, 35.36554092138188]
                ]
            ]
        },
        "properties": {
            "off_nadir_min": 7.4760494,
            "view:sun_azimuth": 159.54324333333332,
            "acquisition_id": "10300100B3841C00",
            "pan_resolution_max": 0.47500458,
            "date": "2021-01-16",
            "datetime": "2021-01-16T18:02:57.170983Z",
            "constellation": "digitalglobe",
            "tile:cloud_free_percentage": 100.0,
            "pan_resolution_avg": 0.47164591166666664,
            "pan_resolution_min": 0.47035816,
            "modified": "2021-05-18T01:07:33Z",
            "view:sun_elevation": 31.5245595,
            "multi_resolution_avg": 1.8871270166666667,
            "multi_resolution_min": 1.8817121,
            "tile:cloud_percentage": 0.0,
            "view:off_nadir": 8.159726833333334,
            "tile:data_percentage": 3.0,
            "off_nadir_max": 9.683383,
            "tile:cloud_polys": null,
            "platform": "worldview-02",
            "multi_resolution_max": 1.9010458,
            "eo:cloud_cover": 1.3208534224506887,
            "tile:quadkey": "031133320000",
            "view:azimuth": 111.309445,
            "instruments": ["VNIR"],
            "tile:zone": 13,
            "tile:no_data_percentage": 97.0,
            "aoi:data_area_sqkm": 0.743,
            "aoi:data_percentage": 4,
            "aoi:cloud_free_percentage": 4,
            "cell_id": "Z13-031133320302"
        },
        "stac_version": "1.0.0",
        "stac_extensions": ["https://stac-extensions.github.io/eo/v1.0.0/schema.json", "https://stac-extensions.github.io/view/v1.0.0/schema.json"],
        "bbox": [-106.7616552633806, 35.36549648670249, -106.758117259609, 35.38791075120405],
        "links": [{
            "rel": "self",
            "href": "https://ard.maxar.com/api/v1/metadata/cells/Z13-031133320302/acquisitions/10300100B3841C00?format=stac"
        }, {
            "rel": "collection",
            "href": "https://ard.maxar.com/api/v1/metadata/cells/Z13-031133320302/acquisitions?format=stac"
        }],
        "assets": {
            "preview": {
                "title": "Preview of 10300100B3841C00 in grid cell Z13-031133320302",
                "type": "image/jpeg",
                "roles": ["thumbnail"],
                "href": "https://ard.maxar.com/api/v1/browse/preview/10300100B3841C00/Z13-031133320302"
            }
        },
        "id": "Z13-031133320302/10300100B3841C00"

    }]
}
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