# Google Earth Engine Data API

GDAL/OGR >= 2.4

The driver supports read-only operations to list images and their metadata as a vector layer, using Google Earth Engine REST API.

## Dataset name syntax

The minimal syntax to open a datasource is :

    EEDA:[collection]

where collection is something like projects/earthengine-public/assets/COPERNICUS/S2.

## Open options

The following open options are available :

- COLLECTION=string: To specify the collection if not specified in the connection string.

## Authentication methods

The following authentication methods can be used:

- Authentication Bearer header passed through the EEDA_BEARER or EEDA_BEARER_FILE configuration options.
- Service account private key file, through the GOOGLE_APPLICATION_CREDENTIALS configuration option.
- OAuth2 Service Account authentication through the EEDA_PRIVATE_KEY/ EEDA_PRIVATE_KEY_FILE + EEDA_CLIENT_EMAIL configuration options.
- Finally if none of the above method succeeds, the code will check if the current machine is a Google Compute Engine instance, and if so will use the permissions associated to it (using the default service account associated with the VM). To force a machine to be detected as a GCE instance (for example for code running in a container with no access to the boot logs), you can set CPL_MACHINE_IS_GCE to YES.

## Configuration options

The following configuration options are available :

- EEDA_BEARER=value: Authentication Bearer value to pass to the API. This option is only useful when the token is computed by external code. The bearer validity is typically one hour from the time where it as been requested.
- EEDA_BEARER_FILE=filename: Similar to EEDA_BEARER option, except than instead of passing the value directly, it is the filename where the value should be read.
- GOOGLE_APPLICATION_CREDENTIALS=file.json: Service account private key file that contains a private key and client email
- EEDA_PRIVATE_KEY=string: RSA private key encoded as a PKCS#8 PEM file, with its header and footer. Used together with EEDA_CLIENT_EMAIL to use OAuth2 Service Account authentication. Requires GDAL to be built against libcrypto++ or libssl.
- EEDA_PRIVATE_KEY_FILE=filename: Similar to EEDA_PRIVATE_KEY option, except than instead of passing the value directly, it is the filename where the key should be read.
- EEDA_CLIENT_EMAIL=string: email to be specified together with EEDA_PRIVATE_KEY/EEDA_PRIVATE_KEY_FILE to use OAuth2 Service Account authentication.

## Attributes

The layer field definition is built by requesting a single image from the collection and guessing the schema from its "properties" element. The "eedaconf.json" file from the GDAL configuration will also be read to check if the collection schema is described in it, in which case the above mentioned schema guessing will not done.

The following attributes will always be present:

Field name | Type | Meaning | Server-side filter compatible
--- | --- | --- | ---
name | String | Image name (e.g. projects/earthengine-public/assets/COPERNICUS/S2/20170430T190351_20170430T190351_T10SEG) | No
id | String | Image ID; equivalent to name without the "projects/*/assets/" prefix (e.g. users/USER/ASSET) | No
path | String | (Deprecated) Image path; equivalent to id | No
gdal_dataset | String | GDAL dataset name (e.g. EEDAI:projects/earthengine-public/assets/COPERNICUS/S2/20170430T190351_20170430T190351_T10SEG) that can be opened with the Google Earth Engine Data API Image driver | No
startTime | DateTime | Acquisition start date | Yes (restricted to >= comparison on top level)
endTime | DateTime | Acquisition end date | Yes (restricted to <= comparison on top level)
updateTime | DateTime | Update date | No
sizeBytes | Integer64 | File size in bytes | No
band_count | Integer | Number of bands | No
band_max_width | Integer | Maximum width among bands | No
band_max_height | Integer | Maximum height among bands | No
band_min_pixel_size | Real | Minimum pixel size among bands | No
band_upper_left_x | Real | X origin (only set if equal among all bands) | No
band_upper_left_y | Real | Y origin (only set if equal among all bands) | No
band_crs | String | CRS as EPSG:XXXX or WKT (only set if equal among all bands) | No
other_properties | String | Serialized JSon dictionary with key/value pairs where key is not a standalone field. | No

"Server-side filter compatible" means that when this field is included in an attribute filter, it is forwarded to the server (otherwise only client-side filtering is done).

### Geometry

The footprint of each image is reported as a MultiPolygon with a longitude/latitude WGS84 coordinate system (EPSG:4326).

### Filtering

The driver will forward any spatial filter set with SetSpatialFilter() to the server. It also makes the same for simple attribute filters set with SetAttributeFilter(). The 3 boolean operators (AND, OR, NOT) and the comparison operators (=, <>, <, <=, > and >=) are supported.

### Paging

Features are retrieved from the server by chunks of 1000 by default (and this is the maximum value accepted by the server). This number can be altered with the EEDA_PAGE_SIZE configuration option.

### Extent and feature count

The reported extent and feature count will always be respectively (-180,-90,180,90) and -1, given there is no way to get efficient answer to those queries from the server.

### Examples

- Listing all images available:

      ogrinfo -ro -al "EEDA:" -oo COLLECTION=projects/earthengine-public/assets/COPERNICUS/S2 --config EEDA_CLIENT_EMAIL "my@email" --config EEDA_PRIVATE_KEY_FILE my.pem

  or

      ogrinfo -ro -al "EEDA:projects/earthengine-public/assets/COPERNICUS/S2" --config EEDA_CLIENT_EMAIL "my@email" --config EEDA_PRIVATE_KEY_FILE my.pem

- Listing all images under a point of (lat,lon)=(40,-100) :

      ogrinfo -ro -al "EEDA:projects/earthengine-public/assets/COPERNICUS/S2" -spat -100 40 -100 40 --config EEDA_CLIENT_EMAIL "my@email" --config EEDA_PRIVATE_KEY_FILE my.pem

- Listing all images available matching criteria :

      ogrinfo -ro -al "EEDA:projects/earthengine-public/assets/COPERNICUS/S2" -where "startTime >= '2015/03/26 00:00:00' AND endTime <= '2015/06/30 00:00:00' AND CLOUDY_PIXEL_PERCENTAGE < 10" --config EEDA_CLIENT_EMAIL "my@email" --config EEDA_PRIVATE_KEY_FILE my.pem

  ## See Also:

  - Google Earth Engine Data API Image driver