Kraken API (Imagery and Analyses)

Legends say that the Kraken was a giant sea creature that was bigger than the eye could see. Sometimes, one wants to get an overview of a bigger area than Ragnar API can provide. Borrowing its name from the Kraken, the sea monster, the Kraken API was born to serve this very need.

The API interfaces imagery and analyses through tiled web map interface.

Available Algorithms

Map Type Supported Imagery Raster Output Vector Output
imagery
truecolor.png
imagery.ski
bands.json

aircraft
gbdx idaho-pansharpened
ab pleiades
pl PSOrthoTile
aircraft.png
segmentation.ski
detections.geojson
area.json

ships
gbdx idaho-pansharpened
ab pleiades
pl PSOrthoTile
ships.png
segmentation.ski

detections.geojson
area.json

wrunc
gbdx idaho-pansharpened
ab pleiades
pl PSOrthoTile



water.png
roads.png
urban.png
nonurban.png
clouds.png
segmentation.ski
area.json





cars
gbdx idaho-pansharpened [1]


cars.png
trucks.png
segmentation.ski
detections.geojson
area.json

containers [2]
gbdx idaho-pansharpened
ab pleiades
containers.png
segmentation.ski
area.json

destruction [4]
gbdx idaho-pansharpened



destruction-medium.png
destruction-heavy.png
road-destruction.png
segmentation.ski
area.json



boats [3]
gbdx idaho-pansharpened
ab pleiades
boats.png
segmentation.ski
detections.geojson
area.json
solar-panels
gbdx idaho-pansharpened

solar-panels.png
segmentation.ski
area.json

pools
gbdx idaho-pansharpened

pools.png
segmentation.ski
detections.geojson
area.json
houses [5]
gbdx idaho-pansharpened



houses.png
construction-medium.png
constructions-early.png
segmentation.ski
detections.geojson
area.json


coal
ee COPERNICUS/S2

coal.png
segmentation.ski
area.json

cranes
gbdx idaho-pansharpened

cranes.png
segmentation.ski
detections.geojson
area.json
lithium
ee COPERNICUS/S2

lithium.png
segmentation.ski
area.json

cows
gbdx idaho-pansharpened

cows.png
segmentation.ski
detections.geojson
area.json
change [6]
gbdx idaho-pansharpened
ab pleiades
pl PSOrthoTile [10]
heatmap.png
heatmap.ski

attention_regions.geojson
bands.json

s2-change [6]
ee COPERNICUS/S2

heatmap.png
heatmap.ski
attention_regions.geojson
bands.json
sar-blobs [7]
ee COPERNICUS/S1_GRD

sar-blobs.png
segmentation.ski
detections.geojson
area.json
sar-change [8]
ee COPERNICUS/S1_GRD

heatmap.png
heatmap.ski
attention_regions.geojson
bands.json
wrunc-change [9]
pl PSOrthoTile [10]










water-added.png
water-removed.png
roads-added.png
roads-removed.png
urban-added.png
urban-removed.png
nonurban-added.png
nonurban-removed.png
clouds-added.png
clouds-removed.png
segmentation.ski
area.json










eme [11]
gbdx idaho-pansharpened

eme.png
segmentation.ski
detections.geojson
area.json
trees
gbdx idaho-pansharpened

trees.png
segmentation.ski
area.json

ndvi [12]
gbdx idaho-pansharpened
pl PSOrthoTile
ee LANDSAT/LC08/C01/T1
ee COPERNICUS/S2
heatmap.png
heatmap.ski


bands.json



ndbi [13]
ee LANDSAT/LC08/C01/T1
ee COPERNICUS/S2
heatmap.png
heatmap.ski
bands.json

ndmi [14]
ee LANDSAT/LC08/C01/T1
ee COPERNICUS/S2
heatmap.png
heatmap.ski
bands.json

weather [15]
pl PSOrthoTile


clouds.png
snow.png
segmentation.ski
area.json


For more information about vector files, see area.json, detections.geojson and attention_regions.geojson formats.

[1]Only images with GSD lower than 0.55.
[2]Detects cargo containers.
[3]Detects boats with length smaller or equal to 30 meters. Note that boats are also detected as ships in ships map type, i.e. boats class is a subset of ships class.
[4]Detects ruins of houses and infrastructure in war-zones.
[5]Detects houses and house constructions (medium and early phases).
[6](1, 2) Detects changes in a new image as compared to an old image.
[7]Detects blobs at open water areas in a SAR (Synthetic-Aperture Radar) image.
[8]Detects changes in a new SAR (Synthetic-Aperture Radar) image compared to an old SAR image.
[9]Detects changes in WRUNC outputs of a new and an old image.
[10](1, 2) Change detection can run only between provider-datasets within supported groups: {gbdx, ab} and {pl}.
[11]Detects earthmoving equipment (excavators, backhoe loaders and bulldozers). Currently works only on images from WV03_VNIR satellite.
[12]Normalized Difference Vegetation Index.
[13]Normalized Difference Buildup Index.
[14]Normalized Difference Metalic Index.
[15]Detects clouds and snow covered land.

Some algorithm SKI files contain sScore. S-score metadatum is a value between 0 and infinity which measures the difference between the input image and the algorithm training set. The larger the value the more error-prone the algorithm gets.

Map and Tiling

Kraken map is Earth surface between -180 to +180 of longitude and -85.051129 to +85.051129 of latitude projected to a square with Web Mercator projection. The map is divided into multiple zoom levels each consisting of a grid of tiles.

A tile is unambiguously identified by \((z, x, y)\) coordinates, where \(z\) represents zoom level, \(x\) represents a horizontal coordinate and \(y\) represents a vertical coordinate. The top-left tile has coordinates \((z, 0, 0)\).

A zoom level is a number that indicates the level of tile’s fine-detail. The lowest zoom level, at which the whole map is rendered to a single tile, is 0. With each successive zoom level, the total number of map tiles quadruples. The zoom level \(z >= 0\) is a grid with \(2^z \times 2^z\) tiles.

A tile is physically represented by one or many files representing area given by the tile boundaries. The files may consist of PNG and other images with dimensions of 256x256 pixels, a GeoJSON or other types of raster and vector data. See Grid Files.

Glossary

  • Kraken map – an individual image or analyses identified with a unique ID.
  • Map type – type of a Kraken map. For example WRUNC or IMAGERY.
  • Grid file – a map is divided into tiles. For every tile (i.e. some zoom, x, y coordinates) there is one or more available grid files (e.g. truecolor.png or detections.geojson).

Release The Kraken!

Kraken release endpoints serve as a preparation and/or re-computation of a map. All release endpoints generate a map ID which can be later used to access the map. A map ID expires in one year.

Generic Kraken Release Endpoints

Kraken API can generate various map types. One can generate a map for a GeoJSON. Release endpoints have uniform URL paths in format: /kraken/release/<map_type>/geojson/{initiate|retrieve}.

Needed Permissions:

  • kraken.release
  • Also a set of permissions in the form <prefix>.<provider>.<dataset> is needed. <prefix> is replaced with algorithms.<name-of-algorithm> or with imagery.images.
POST /kraken/release/{map_type}/geojson/initiate
Request JSON Object:
 

Example request:

{
    "sceneId": "abc",
    "extent": {
        "type": "MultiPolygon",
        "coordinates": [
            [
                [
                    [-122.51747131348, 37.694823535365],
                    [-122.35130310059, 37.694823535365],
                    [-122.35130310059, 37.809919574016],
                    [-122.51747131348, 37.809919574016],
                    [-122.51747131348, 37.694823535365]
                ]
            ]
        ]
    }
}

Example response:

See pipeline initiation.

Max zoom

Max zoom is determined by the following formula:

\[z_{max} = \lceil log_2(\frac{4 \cdot 10^7 \cdot cos(\frac{l \cdot \pi}{180})}{256 \cdot r_e}) \rceil\]

where \(l\) is latitude of the scene footprint centroid and \(r_e\) is the effective resolution in meters per pixel.

Effective resolution for the map can be determined by the following pseudo code:

if release_type == 'imagery':
    r_e = min(r for b in bands for r in (b.approx_res_x, b.approx_res_y))
elif provider == 'pl':
    r_e = 3.125
else:
    r_e = 0.5

Needed Permissions: kraken.release

POST /kraken/release/{map_type}/geojson/retrieve

Example request:

See pipeline retrieve.

Response JSON Object:
 
  • mapId (string) – map ID to be used to access map tiles.
  • maxZoom (int) – maximum zoom available for returned mapId.
  • tiles (list) – List of tiles which were successfully created, the system may be unable to release some of the requested tiles. This is always a subset of requested tiles. It is guaranteed that at most four tiles, all at equal zoom level, are returned. User is allowed to request any descendant tile, note that some child tiles of tiles may be missing.

Example response:

{
    "mapId": "xyz",
    "maxZoom": 19,
    "tiles": [
        [19, 83861, 202628]
    ]
}

Release Pairwise Map Types

General Change Detection and WRUNC Change map types use two scenes as input and are released and retrieved in the following manner.

Needed Permissions: See generic initiate endpoint.

POST /kraken/release/<map_type>/geojson/initiate
Request JSON Object:
 
  • oldSceneId (string) – required; ID of an old scene.
  • newSceneId (string) – required; ID of a scene in which changes will be detected as compared to “old scene”.
  • extent (object) – required; area of interest which must intersect with intersection of old and new scene’s footprints. The area must be allocated using Credits API if the imagery is high-resolution.
POST /kraken/release/<map_type>/geojson/retrieve

See generic retrieve endpoint.

Grid Files

A tile can be downloaded on https://spaceknow-kraken.appspot.com/kraken/grid/<map_id>/<geometry_id>/<z>/<x>/<y>/<file_name>, where map_id is an ID of a map, geometry_id is either - or an ID of a geometry from GeoJSON API, z is zoom level, x and y are horizontal and vertical coordinates of the tile.

Each map type has different set of available tiles (file_name in the URL). See the documentation of individual Kraken release endpoints above.

If geometry_id is not - then the tile is clipped to the GeoJSON.

.png tile is a RGBA PNG and polygon is drawn to the PNG alpha channel.

For example this URL https://spaceknow-kraken.appspot.com/kraken/grid/xyz/-/19/83861/202628/truecolor.png contains a PNG tile that shows the city of San Francisco (\(x = 83861, y = 202628\)) at zoom level 19. The tile is from a map with ID abc and is not clipped (geometry_id is -).

Other examples are:

  • https://spaceknow-kraken.appspot.com/kraken/grid/abc/-/19/83861/202628/aircraft.png
  • https://spaceknow-kraken.appspot.com/kraken/grid/abc/-/19/83861/202628/segmentation.ski
  • https://spaceknow-kraken.appspot.com/kraken/grid/abc/-/19/83861/202628/detections.geojson
  • https://spaceknow-kraken.appspot.com/kraken/grid/abc/-/19/83861/202628/area.json
  • https://spaceknow-kraken.appspot.com/kraken/grid/abc/-/19/83861/202628/bands.json

Error Status Codes

  • 400 – invalid request: a possible reason is invalid or expired map ID.
  • 401 – given map ID doesn’t include requested tile.
  • 404 – requested tile doesn’t exist: data are not available or the area of the tile cannot be analyzed.