TanagerScene
Imagery Products Overview
The TanagerScene products include Visual, Radiance, and Surface Reflectance hyperspectral imagery in HDF5 file format.
Tanager Chunking Strategy
A single Tanager collection can be long and to process and deliver Tanager assets with more reasonable file sizes, the collections are dynamically chunked. Each collect is separated into TanagerScenes based on the following set of rules:
- A scene is at least 325 lines long.
- A scene is at most 750 lines long.
- The strategy seeks to produce square-ish scenes.
- All scenes within a single collection are approximately the same size. The worst case scenario is that a collect will have only two different scene sizes. These two sizes will vary by only a single line.
Example chunking below. Each | BOX | is a TanagerScene.
1700 line collect: | 0:567 | 567:1134 | 1134:1700 |
2600 line collect: | 0:650 | 650:1300 | 1300:1950 | 1950:2600 |
Tanager Ortho Products
The Tanager Ortho Scene product is orthorectified and the product was designed for a wide variety of applications that require imagery with an accurate geolocation and cartographic projection. It has been processed to remove distortions caused by terrain and can be used for cartographic purposes. The Ortho Scenes are delivered as visual (RGB), top-of-atmosphere radiance and surface reflectance products. Ortho Scenes are radiometrically-, sensor-, and geometrically-corrected products that are projected to a cartographic map projection. The geometric correction uses fine Digital Elevation Models (DEMs) with a post spacing of between 10 and 90 meters.
Ground Control Points (GCPs) are used in the creation of every image and the accuracy of the product will vary from region to region based on available GCPs. Computer vision algorithms are used for extracting feature points such as OpenCV’s STAR keypoint detector and FREAK keypoint extractor. The GCP and tiepoint matching is done using a combination of RANSAC, phase correlation and mutual information.
Tanager Basic Products
The Tanager Basic Scene products are unorthorectified, providing imagery as seen from Tanager without any geolocation corrections inherent in the imaging process. It has a scene based framing, and is not mapped to a cartographic projection. This product line is available in HDF-EOS5 format.
The Tanager Basic Scene product contains the hyperspectral data in image space and a separate geolocation array (longitude and latitude information) that has been processed to remove distortions caused by terrain and geometric sensor distortions. The Basic Scene product is designed for users that want to orthorectify the product themselves with the help of the provided geolocation array or for users with advanced image processing capabilities and a desire to geometrically correct the product themselves.
TanagerScene Item Type
Tanager Scene — Extent: Global, 2024-01-01T00:00:00Z to present
Description
Tanager Hyperspectral Imagery
TanagerScene Assets
Item Properties
| Field | Description | Data Type |
|---|---|---|
| acquired | Timestamp representing the nominal date and time of acquisition (in UTC). | datetime |
| cloud_percent | The percentage of the image obscured by clouds. | range-integer |
| collection_mode | Imaging sensitivity mode | enum-string |
| geometry | Geospatial extent of image, represented as a geo-json Polygon vs Multi-Polygon. | geometry |
| ground_control | If the image meets the positional accuracy specifications this value will be true. If the image has uncertain positional accuracy, this value will be false. | boolean |
| gsd | The ground sampling distance of the image acquisition. | float |
| id | Provider-specific unique identifier | string |
| item_type | The identifier of the asset | string |
| light_haze_percent | The percentage of the image containing light haze. | range-integer |
| pixel_resolution | Pixel resolution of the ortho product files in meters. | range-float |
| provider | Imagery Provider, as a member of the enum of known providers. | enum-string |
| published | Timestamp representing the first publish of the item id (in UTC). | datetime |
| publishing_stage | Metric for an item's publishing stage. 'Preview' items have not been rectified and may change substantially upon subsequent publish. 'Standard' items are rectified and subject to minimal change upon subsequent publish. 'Finalized' items are rectified and additional changes are not expected. | enum-string |
| quality_category | Metric for image quality. To qualify for 'standard' image quality an image must meet the following criteria: sun altitude greater than or equal to 10 degrees, off nadir view angle less than 20 degrees, and saturated pixels fewer than 20%. If the image does not meet these criteria it is considered 'test' quality. | enum-string |
| satellite_azimuth | Spacecraft off track pointing direction, in degrees (0-360) | range-float |
| satellite_id | human-readable identifier for the satellite(e.g. SSC11, 0c18, RapidEye-2, Sentinel-2A) | string |
| strip_id | Unique Identifier for the underlying RapidEye collect spanning the Item's capture. | string |
| sun_azimuth | Angle from true north to the sun vector projected on the horizontal plane in degrees. | range-float |
| sun_elevation | Elevation angle of the Sun in degrees. | range-float |
| updated | Timestamp representing the last update of the item id (in UTC). | datetime |
| view_angle | Spacecraft across track viewing angle used for imaging. | range-float |