Work with InSAR metadata¶

The first examples continue from the Item created in the tutorial.

Update or remove one field¶

insar = InsarExtension.ext(item)
insar.temporal_baseline = 24
insar.processing_dem = None
assert "insar:processing_dem" not in item.properties

ext(item) requires the extension to be declared already. Use add_if_missing=True when first attaching it. Assigning None removes a field.

apply() sets every supported field. Omitted arguments become None and remove existing values. Use individual setters to preserve other fields.

Attach asset fields¶

asset = pystac.Asset(href="https://example.org/interferogram.tif", media_type="image/tiff")
item.add_asset("interferogram", asset)
asset_insar = InsarExtension.ext(asset, add_if_missing=True)
assert asset_insar.temporal_baseline is None
asset_insar.temporal_baseline = 12
assert asset.extra_fields["insar:temporal_baseline"] == 12.0
assert insar.temporal_baseline == 24.0

Attach an asset to its owner before wrapping it so extension membership can be checked or added on the owner. The asset wrapper reads and writes asset.extra_fields; it does not inherit missing values from Item properties. Collection assets use the same wrapper.

Manage Collection summaries¶

Use InsarExtension.summaries() for Collections. Passing a Collection to InsarExtension.ext() raises pystac.ExtensionTypeError.

collection = pystac.Collection(
    id="example-insar-collection",
    description="Synthetic InSAR products",
    extent=pystac.Extent(
        pystac.SpatialExtent([[-180.0, -90.0, 180.0, 90.0]]),
        pystac.TemporalExtent([[reference_datetime, secondary_datetime]]),
    ),
    license="proprietary",
)
summaries = InsarExtension.summaries(collection, add_if_missing=True)
summaries.apply(
    reference_datetime=reference_datetime,
    processing_dem="COP-DEM GLO-30",
    geocoding_dem="COP-DEM GLO-30",
)
assert collection.summaries.lists["insar:processing_dem"] == ["COP-DEM GLO-30"]
assert summaries.reference_datetime == reference_datetime

summaries.processing_dem = None
assert "insar:processing_dem" not in collection.summaries.lists

The summary helper supports reference datetime, processing DEM, and geocoding DEM. Each setter replaces the summary with a single-element list; each getter reads only the first element. Assigning None removes the summary. Its apply() method clears omitted values, just like the Item helper.

Use Collection item asset definitions¶

collection.item_assets = {
    "interferogram": pystac.ItemAssetDefinition(
        {"type": "image/tiff", "roles": ["data"]}
    ),
}
definition = collection.item_assets["interferogram"]
definition_insar = InsarExtension.ext(definition, add_if_missing=True)
definition_insar.processing_dem = "COP-DEM GLO-30"
assert definition.properties["insar:processing_dem"] == "COP-DEM GLO-30"

Retrieve definitions through collection.item_assets so they have an owner. Fields are written to the definition's properties dictionary, and the extension is declared on its Collection.