Coverages

This document describes the data model layout of the coverages, the internal structure of earth observation products, collections and data files. It also shows how these models can be interacted with via the command line interfaces.

Data model

../_images/models.png

The data model is loosely based on the OGC coverages data models, especially with the EO Application Profile for WCS 2.0.

Coverage Type

The coverage type describes the internal structure of coverages of a specific type. The coverage type is comprised of a list of field types that define the structure and metadata of a specific field of Data, called the Field Type.

The coverage type has a unique name to allow its identification.

Product Type

The product type model allows to define the structure of products by limiting the coverage types each coverage is allowed to have for products of this product type.

Additionally, each Product Type can be associated with a number of Browse Type and Mask Type that define the masks and browses that products of that type are allowed to have.

Browse Type

A browse type defines a typical visual representation of a product. For this purpose, it allows to define expression, scaling ranges and nodata values to generate that representation (browse).

A browse type can either define a single output band (grey), three output bands (RGB) or four output bands (RGBA).

Expressions must follow Python syntax rules but can only contain simple arithmetic expressions. All identifiers must be names of field types that are linked to coverage types in the list of allowed coverage types of the referenced product type.

Mask Type

These type models define what polygon masks can be linked to products of that product type and whether the masks define areas of validity or invalidity.

Collection Type

These type models allow to define the shape of collections by allowing to limit the product types and coverage types of product and coverages that can be added to collections of their respective collection types.

EOObject

This is the base model class for uniquely identifier geospatial objects. EOObject provides the fields identifier (mandatory and unique), the footprint (its geometry) and its temporal distribution: begin_time and end_time.

All objects inheriting from EOObject share a common pool of identifier. Thus, it is, for example, not possible for a collection to have the same identifier as a product or coverage.

Grid

A grid defines a regularly spaced grid comprised of up to four axes. Each axis can either be of spatial, temporal, evelation or other type. For each defined axis, the regular offset value must be specified.

Each grid is associated with a coordinate reference system.

A grid can be named, making it easier to manage.

A grid does not provide an actual location or area, this information can only be obtained with a Grid Fixture in conjunction with a grid.

Mosaic

This model is a collection of homogenenous coverages, all sharing the same coverage type and grid. This allows to access the mosaic as if it were a single coverage by combinig the data from all its comprising elements.

Coverage

A coverage is an n-dimensional raster data set comprised of several fields.

A coverage is linked to at least one ArrayDataItem, a reference to the actual raster data.

TODO: rel OGC coverage

Product

A product is a sort of collection of geospatially and temporally very close objects.

A product can combine multiple coverages which cover the same are but cannot be combined to a single coverage because of different resolutions.

In some cases, coverages are not necessary at all, and just provide data items for a binary download and browses for previewing.

Browse

A browse is always associated with a product and serves as a preview to the actual data. Browses are materialized files that are either pre-generated or can be generated from the coverage data.

Mask

Masks allow to specify regions in products for some kind of flag for example validity. Each mask is linked to a Mask Type.

Collection

Multiple coverages and products can be grouped in a collection. This relationship is many-to-many, so each product/coverage can be inserted into multiple collections.

When a collection is linked to a Collection Type only Products and Coverages whose types are of the set of allowed coverage/product types can be inserted.

Command Line Interfaces

The following command line interfaces can be executed via the manage.py utility of the instance. All commands are related to one of the models above and use sub-commands for specific tasks.

coveragetype

This command manages Coverage Type models and allows to inspect the currently available ones.

create

Creates a new Coverage Type with specifications from the parameters.

name

the name of the Coverage type to create

--field-type

add a new field type to the definition. Must be the five parameters: identifier, description, definition, unit-of-measure, and wavelength. Can be used multiple times to add more than one field.

TODO: example

import

imports one or more Coverage Type definition from JSON files.

locations*

a list of filenames to import definitions from

--in, -i

read from stdin instead from a file

TODO: show definition, example

delete

deletes a Coverage Type

name

the name of the Coverage Type to delete

--force, -f

delete the Coverage Type, even if it is still in use. This cascades and deletes all Coverages of that type as well.

list

lists the stored Coverage Types

--no-detail

disable the printing of details of the coverage type.

producttype

This command manages Product Type models. It provides the following sub-commands:

create

creates a new Product Type.

name

the name of the Product Type to create

--coverage-type

the Coverage Type name to add to this product type. Can be specified multiple times.

--mask-type

the name of a to be created mask type.

--validity-mask-type

the name of a to be created validity mask type.

--browse-type

the name of a to be created Browse type. It is recommended to use browsetype create instead.

delete

deletes a Product Type

name

the name of the Product Type to delete

list

lists all available Product Types

--no-detail

disable the printing of details of the product type.

browsetype

This command allows to create, delete and list Browse Type models. Since Browse Types are always associated with a Product Type the first argument is always the name of a Product Type.

create

creates a new Browse Type for a Product Type. Valid field names for the --red, --green, --blue, and --alpha parameters are the names from the field names of the linked Coverage Types of the associated Product Type.

product_type_name

the Product Type to create the Browse Type for

[browse_type_name]

the name of the Browse Type. Can be omitted, to define the default Browse Type.

--red, --grey, -r

the field name or mathemathical expression to use as the red output band (or grey, if used for a single band output).

--green, -g

the field name or mathemathical expression to use as the green output band.

--blue, -b

the field name or mathemathical expression to use as the blue output band.

--alpha, -a

the field name or mathemathical expression to use as the green output band.

--red-range, --grey-range

the low and high border of values to apply a linear stretch for the red output band.

--green-range

the low and high border of values to apply a linear stretch for the green output band.

--blue-range

the low and high border of values to apply a linear stretch for the blue output band.

--alpha-range

the low and high border of values to apply a linear stretch for the alpha output band.

--red-nodata, --alpha-nodata

the nodata value for the red output band. This is applied after the stretch and will result in transparent pixels for this value.

--green-nodata

the nodata value for the green output band. This is applied after the stretch and will result in transparent pixels for this value.

--blue-nodata

the nodata value for the blue output band. This is applied after the stretch and will result in transparent pixels for this value.

--alpha-nodata

the nodata value for the alpha output band. This is applied after the stretch and will result in transparent pixels for this value.

delete

deletes a no longer needed Browse Type.

product_type_name

the Product Type to delete the Browse Type from

[browse_type_name]

the name of the Browse Type to delete

list

lists all Browse Types for a given Product Type.

product_type_name

the Product Type to list the Browse Types for

masktype

This command allows to create, delete and list Mask Type models. Since Mask Types are always associated with a Product Type the first argument is always the name of a Product Type. The sub-commands are in detail:

create

creates a new Mask Type for a Product Type

product_type_name

the Product Type to create the Mask Type for

mask_type_name

the Mask Type name to create

--validity

whether this mask denotes valid or invalid values. By default, it uses invalidity.

delete

deletes a Mask Type.

product_type_name

the Product Type to delete the Mask Type from

mask_type_name

the Mask Type name to delete

list

lists all Mask Types for a given Product Type.

product_type_name

the Product Type to list the Mask Type of

collectiontype

This command manages Collection Type models using the following sub-commands:

create

creates a new Collection Type.

name

the name of the Collection Type

--coverage-type, -c

the name of an existing Coverage Type, that shall be linked to this Collection Type. Only Coverages can be inserted into Collection when the Coverages Type is part of the Collections Type.

--product-type, -p

the name of an existing Product Type, that shall be linked to this Collection Type. Only Products can be inserted into Collection when the Product Type is part of the Collections Type.

delete

deletes a Collection Type.

name

the name of the Collection Type to delete

--force, -f

forces the deletion of all still existing Collections using this Collection Type.

list

lists all available Collection Types.

--no-detail

Disable the printing of details of the Collection types.

grid

This command allows to create and delete named Grid Model instances.

create

this creates a Grid.

name

the name of the Grid to create

coordinate_reference_system

the definition of the coordinate reference system. Either an integer (the EPSG code), or the URL, WKT or XML definiton.

The following parameters can be used up to four times in order to define multiple axes.

--name, --axis-name, -n

the name of the n-th axis to add to the Grid.

--type, --axis-type, -t

the type of the n-th axis to add to the Grid.

--offset, --axis-offset, -o

the fixed axis offset step of the n-th axis to add to the Grid.

delete

deletes a Grid.

name

the name of the Grid to delete.

coverage

this command allows the registration and deregistration of Coverage Model instances.

register

this sub-command registers a Coverage.

--data, -d

this specifies a location for raster data. Multiple values can be used to denote that the data resides on a storage. If used in that way the first value can also be the name of a named storage. This parameter can be used multiple times, when the raster data is split into multiple files.

--meta-data, -m

similarly to the --data parameter, this parameter denotes a reference to meta-data. The same rules as for the --data parameter also apply here.

--type, --coverage-type, -t

specify the Coverage Type for this Coverage. By default no Coverage Type is used.

--grid, -g

specify the named Grid Model to use. By default an anonymous Grid is used with the CRS of the raster data files.

--size, -s

specifies the size of the Coverage. This overrides the size extracted from the metadata/data. Must specify the size for each axis of the Grid.

--origin, -o

overrides the origin of the Coverage. Must provide a value for each axis of the Grid.

--footprint, -f

overrides the geographical footprint of the Coverage. Must be a valid WKT geometry.

--footprint-from-extent

The footprint polygon shall be calculated from the Coverages extent.

--identifier, -i

override the Coverages identifier.

--identifier-template

allows the construction of the final identifier from a template. Substitution values are passed in from the extracted metadata. e.g: {identifer}__B01.

--begin-time, -b

override the begin timestamp of the Coverage. Must be a valid ISO 8601 datetime string.

--end-time, -e

override the end timestamp of the Coverage. Must be a valid ISO 8601 datetime string.

--product, --product-identifier, -p

specify the Product identifier this Coverage shall be associated with. The Product must already be registered.

--collection, --collection-identifier, -c

specify the Collection identifier this Coverage shall be inserted into. The Collection must already exist.

--replace, -r

replace an already existing Coverage with the same identifier.

--use-subdatasets, --subdatasets

specify to interpret colons in the filename as subdataset specifiers.

--print-identifier

this switch prints the final identifier (after metadata extraction and potential templating) to stdout upon successful registration.

deregister

this sub-command de-registers the Coverage with the provided identifier.

identifier

the Coverages identifier

--not-refresh-collections

this command will update all Collections metadata (footprint, begin-/end time) unless this switch is set.

--all, -a

When this flag is set, all the Coverages are selected to be derigesterd.

product

this command manages Product Model instances.

register

this sub-command registers products.

--identifier, -i

override the Product identifier.

--identifier-template

allows the construction of the final identifier from a template. Substitution values are passed in from the extracted metadata. e.g: {identifer}__B01.

--footprint

overrides the geographical footprint of the Product. Must be a valid WKT geometry.

--begin-time

override the begin timestamp of the Product. Must be a valid ISO 8601 datetime string.

--end-time

override the end timestamp of the Product. Must be a valid ISO 8601 datetime string.

--set, -s

sets a specific metadata value for that product. This parameter always uses two values: the name of the parameter key and its value. TODO: possible metadata keys to set

--metadata-file

adds a metadata file to the product. As with file links for Coverages, the product file can be located on a storage. For these cases, multiple values can be used to specify the chain of locations.

--type, --product-type, -t

specify the Product Type for this Product. By default no Product Type is used.

--mask, -m

specify a mask file to be added to this product. Must be two values: the masks name and its file location.

--mask-geomety, -g

specify a mask using its geometry directly. Must be two values: the masks name and its WKT geometry representation.

--no-extended-metadata

when this flag is set, only the basic metadata (identifier, footprint, begin- and end-time) is stored.

--no-masks

when this flag is set, no masks will be discovered.

--no-browses

when this flag is set, no browses will be discovered.

--no-metadata

when this flag is set, no metadata files will be discovered.

--package

specify the main data package for this Product.

--collection, --collection-identifier, -c

specify the Collection identifier this Product shall be inserted into. The Collection must already exist.

--replace

replace an already existing Product with the same identifier.

--print-identifier

this switch prints the final identifier (after metadata extraction and potential templating) to stdout upon successful registration.

deregister

deregisters a Product.

identifier

the identifier of the Product to deregister.

--all, -a

When this flag is set, all the Coverages are selected to be derigesterd.

discover

print the contents of the main package file of a Product.

identifier

the identifier of the Product to discover.

[pattern]

a filename glob pattern to filter the resulting filenames

browse

this command allows to manage Browse Model instances of a Product Model.

register

this sub-command registers a Browse to a Product.

identifier

the Product identifier to register the Browse for.

location

the storage location of the Browse.

--type

the Browse Type name of that Browse.

generate

TODO

deregister

TODO

mask

this command allows to manage Mask Model instances of a Product Model.

register

registers a Mask for a Product.

identifier

the Product identifier to register the Mask for.

--type

the Mask Type name of that Mask.

--location

the storage location of the Mask.

--geometry

the inline WKT geometry for the mask.

deregister_parser

deregisters a Mask from a Product

identifier

the Product identifier to deregister the Mask from.

collection

this command manages Collection Model instances. As usual, it uses sub-commands to allow fine control over the specific aspects and tasks of a Collection.

create

creates a new Collection.

identifier

the identifier for the new Collection.

--type, -t

specify a Collection Type for this new Collection.

--grid, -g

specify a Grid for this Collection.

--set, -s

set or override Collection metadata. TODO: what keys?

delete

this sub-command deletes a Collection.

identifier

the identifier of the Collection to delete

--all, -a

When this flag is set, all the collections are selected to be derigesterd.

insert

with this sub-command one or more Coverage Model instances or Product Model instances can be inserted into the collection. This command checks whether the to be inserted objects are of the allowed types when a Collection Type is set for this Collection.

identifier

the identifier of the Collection to insert objects into.

object_identifiers+

the list of object identifiers (either Products or Coverages) to insert into the Collection.

exclude

this command allows to remove one or more objects from a collection.

identifier

the identifier of the Collection to exclude objects from.

object_identifiers+

the list of object identifiers (either Products or Coverages) to exclude from the Collection.

purge

this command purges all Coverages and Products from this Collection, leaving it effectively empty.

TODO: not yet implemented

summary

collects metadata from all entailed Products and Coverages to generate a summary that is stored in the Collection. This allows a quick overview of the metadata ranges and specific values of all objects in the collection.

identifier

the Collection identifier to generate the summary for

–products/–no-products

whether or not to generate a Product metadata summary.

–coverages/–no-coverages

whether or not to generate a Coverage metadata summary.

mosaic

this command manages Mosaic Model instances with a variety of sub-commands.

create

creates a new Mosaic.

identifier

the identifier of the Mosaic to create.

--type, -t

the Coverage Type name for the Mosaic to create.

--grid, -g

the Grid to use for the Mosaic.

delete

deletes a Mosaic.

identifier

the identifier of the Mosaic to delete.

insert

insert one or more Coverages into the Mosaic.

identifier

the identifier of the Mosaic to insert Coverages into.

coverage_identifiers+

the Coverage identifiers to insert into the Mosaic.

exclude

exclude one or more Coverages from the Mosaic.

identifier

the identifier of the Mosaic to exclude Coverages from.

coverage_identifiers+

the Coverage identifiers to exclude from the Mosaic.

refresh

refresh the summary metadata of the Mosaic.

identifier

the identifier of the Mosaic to generate the metadata.

purge

TODO not implemented

id

this command allows to introspect the contents of the instances database.

check

this subcommand allows to check whether or not an object is registered. The return value of this command indicates whether such an object exists.

identifiers+

the identifier(s) to check for existence.

--type, -t

limit the check to the given object type (i.e: Coverage, Product, Collection, or Mosaic). By default the search is for any EOObject.

list

this command lists the contents of the database and prints the objects on on the terminal. Filters can be applied to limit the search.

identifiers*

limit the output to the given identifiers.

--type, -t

limit the listing to the given object type (i.e: Coverage, Product, Collection, or Mosaic). By default the search is for any EOObject.

--recursive, -r

do a recursive lookup into the given collections.

--suppress-type, -s

when printing an object, suppress the type and only print the identifier

--collection, -c

limit the search to this collection only. Can be passed multiple times to search across multiple collections.

mapcache

this command allows to generate an index database to be used for mapcache time dimensions.

sync

this sub-command synchronizes a mapcache index database. The output will be written to the <collection-name>.sqlite files for each available collection in the current working directory.

The schema of the database will be the following:

CREATE TABLE "time" (
    "start_time" timestamp with time zone NOT NULL,
    "end_time" timestamp with time zone NOT NULL,
    "minx" double precision NOT NULL,
    "miny" double precision NOT NULL,
    "maxx" double precision NOT NULL,
    "maxy" double precision NOT NULL
)
--force, -f

force the re-generation of the index files.

--unique-times, -u

force unique time entries. This combines the extent of all objects with overlapping time spans.

--no-index

this flag prohibits the creation of an internal database index.

stac

This command allows to register Products and their related data from `STAC Items`_.

register

this sub-command registers a STAC Item as a Product and its raster data as Coverages.

--in, -i

Read the STAC Item from stdin instead from a file.

--type TYPE_NAME, --product-type TYPE_NAME, -t TYPE_NAME

The name of the product type to associate the product with. Optional.

--replace, -r

Optional. If the product with the given identifier already exists, replace it. Without this flag, this would result in an error.

types

this sub-command extracts all the relevant information to generate Product Types, Coverage Types and their related types to allow a subsequent registration.

--in, -i

read the STAC Item from stdin instead from a file.

--type TYPE_NAME, --product-type TYPE_NAME, -t TYPE_NAME

the name of the new product type. Optional.