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 quite long and in order to process and deliver Tanager assets with more reasonable file sizes, the collections will be dynamically chunked. Each collect will be separated into TanagerScenes based on a 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.
Item Properties¶
| Parameter | Description | Type |
|---|---|---|
| _permissions | Assets available for the item which the authenticated user has permission to download. | array |
| geometry | Geographic boundary of the item’s footprint, formatted as a GeoJSON polygon. | json |
| id | Globally unique item identifier | string |
| acquired | The RFC 3339 acquisition time of the image. | datetime |
| cloud_percent | Percent of cloud values in the dataset. Cloud values represent scene content areas (non-blackfilled) that contain opaque clouds which prevent reliable interpretation of the land cover content. | double |
| collection_mode | Maximum Sensitivity (4x8), Standard Sensitivity (1x8), Glint | string |
| 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 average ground sampling distance of the associated Item. Computed for each item to account for variations over the length of a collection. | double |
| item_type | The name of the item type. For example, TanagerScene or TanagerMethane. | string (e.g. TanagerScene) |
| light_haze_percent | Percent of light haze values in the dataset. Light haze values represent scene content areas (non-blackfilled) that contain thin low altitude clouds, higher altitude cirrus clouds, soot and dust which allow reliable recognition of land cover features, and have up to +/-10% uncertainty on commonly used indices (EVI and NDWI). | double |
| pixel_resolution | Pixel resolution of the ortho products associated with this Item. | double |
| provider | Name of the imagery provider. | string (e.g. "tanager","planetscope", "skysat") |
| published | The RFC 3339 timestamp at which this item was added to the API. | datetime |
| publishing_stage | Stage of publishing for an item. TanagerScene items will be first published and remain in the “finalized” stage. | string |
| quality_category | Metric for image quality. To qualify for “standard” image quality an image must meet a variety of quality standards. If the image does not meet these criteria it is considered “test” quality. | string: “standard” or “test” |
| satellite_azimuth | Tanager’s off track pointing direction, in degrees (0-360). | double |
| satellite_id | Globally unique identifier of the satellite that acquired the underlying imagery. I.E. 4001 | string |
| strip_id | The unique identifier of the image strip that the item came from. | string |
| sun_azimuth | The angle of the sun, as seen by the observer, measured clockwise from the north (0 - 360). | double. |
| sun_elevation | The angle of the sun above the horizon (0 - 90). | double |
| updated | The RFC 3339 timestamp at which this item was updated in the API. | datetime |
| view_angle | The satellite’s across-track, off-nadir viewing angle. | double |
Available Asset Types¶
| Asset-Type | Description |
|---|---|
Ortho Radiance Scene ortho_radiance_hdf5 |
Orthorectified, Top of atmosphere radiance (at sensor) calibrated, in HDF5 format. |
Basic Radiance Scene basic_radiance_hdf5 |
Unorthorectified, Top of atmosphere radiance (at sensor) calibrated, in HDF5 format. Not projected to a cartographic projection. |
Ortho Surface Reflectance Scene ortho_sr_hdf5 |
Orthorectified, atmospherically corrected surface reflectance product, in HDF5 format. |
Basic Surface Reflectance Scene basic_sr_hdf5 |
Unorthorectified, atmospherically corrected surface reflectance product, in HDF5 format. Not projected to a cartographic projection. |
Ortho Visual Scene ortho_visual |
Orthorectified red, green, blue (RGB) visual image with color-correction. |
Ortho Beta Usable Data Mask (UDM) ortho_beta_udm |
Orthorectified usable data mask (in beta), in GeoTIFF format. |
Basic Beta UDM basic_beta_udm |
Unorthorectified usable data mask (in beta), in GeoTIFF format. |
Geolocation Array geolocation_array |
Longitudes and Latitudes in WGS84 of centers of pixels, in GeoTIFF format. |
Recent Monthly Basemap recent_monthly_basemap |
RGB contextual baselayer from the most recent PlanetScope Global Monthly Basemap, in GeoTIFF format. |
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