Frames and STAC items

A frame is the basic unit of content you can purchase from the ICEYE public catalog. On this page we explain what a frame is and how frames are related to STAC items.

What is a frame?

A frame is the basic constituent of an image that can be packaged in a product (STAC item).

For most imaging modes, an image consists of a single frame, but in the case of Strip and Scan (where the image can be extended in the direction of flight), the image is broken up into multiple frames:

Single or multiple Imaging modes

Single frame

Spot, Spot Fine, Spot Extended Area, Dwell, Dwell Fine

Multiple frames

Strip, Scan

Breaking long images into frames is done in order to avoid the challenges posed by processing extra long data sets. The multiplicity of frames also reflects the underlying cost of acquisition, because an image with multiple frames has a longer image duration and downlink time.

You can get more information on frames by inspecting the tables from the Imaging Modes chapter of the Data Product Specification. The Nominal Collection Duration[sec] entry gives the duration for collecting a single frame. If the Maximum Collection Duration[sec] is greater than the nominal collection duration, this implies that the image can consist of multiple frames.

Although most frames available in the public catalog have the usual Nominal Collection Duration[sec], as documented in the Data Product Specification, there are some legacy STAC items and custom STAC items that might deviate from this (shorter or longer).

How frames are related to STAC items

The following diagram gives an overview of the flow for imaging acquisition, which illustrates how each frame is related to the corresponding STAC items in the Catalog.

Image acquisition and frames

  1. Acquisition — for a relatively long Stripmap acquisition (for example, 30 seconds), the image might consist of three frames of 10s each, numbered as frames 1, 2, and 3.

  2. Processing — after downlinking the image from the satellite, ICEYE initiates a processing run, which processes the image and generates the products. Note that the entire image is processed at once, generating products for all frames simultaneously

  3. Publication to Catalog — when the image products are published to the Catalog, STAC items are added for each of the products, making it possible to browse for the products in the public catalog.

STAC item

A SpatioTemporal Asset Catalog (STAC) Item (based on the GeoJSON Feature standard) is the standard format for the entries in the ICEYE Catalog. Each product in the Catalog is represented by a STAC item, which can be browsed using the listCatalogItems or searchCatalogItems operations.

API Platform provides additional metadata fields in the GeoJSON Properties object, which can be used in STAC metadata search queries.

Frame ID

A frame ID provides a unique identifier for a frame and you can extract the frame ID from the properties.frame_id property of a STAC item. You need to provide the frame ID when making a purchase from the Catalog.

What you get when you purchase a frame

It is important to understand that, although you view STAC items when browsing the Catalog, the Catalog content is purchased by frame, not by STAC item.

When you purchase a frame:

  • You get all of the products (STAC items) associated with the frame. For example, if you choose to purchase a frame for the GRD product, you also get access to the SLC product for the same frame (except for Scan imaging mode, which produces only the GRD product).

  • If you want to purchase a full Stripmap image consisting of multiple frames, you must purchase each of the frames in the Stripmap image separately.

  • The VID product is composed of multiple looks, not multiple frames, so you only need to purchase a single frame to get a VID product.