GNIP XXX Handling raster mosaics - geosolutions-it/geonode GitHub Wiki

GeoServer supports mosaics with custom dimensions, but there is no way to configure them on GeoNode.

It is proposed to add new (optional) functionalities to provide handling of mosaics.

Operations shall include as a minimum:

• allow users to create a mosaic with custom dimensions (or at least a simplified dimensions set, including a couple of time dimensions and an elevation dimension).
• allow users to add granules to a mosaic.
• allow users to remove granules from a mosaic.

Such mosaics should be recorded as Layers inside GeoNode.

• [Emanuele Tajariol](https://github.com/etj)
• [Alessio Fabiani](https://github.com/afabiani)

TBD

For Review and Comment

GeoNode does not currently provide any way for configuring mosaics.

The Layer class should be modified so that it include information if the given instance is referring to a mosaic, and some related info that need to be persisted.

In the same way the time info is configured for vector layers, a new option will be added to the UPLOADER.OPTIONS dict:

UPLOADER = {
    'BACKEND': 'geonode.importer',
    'OPTIONS': {
        'TIME_ENABLED': True,
        'MOSAIC_ENABLED': True,

When a GeoTIFF is selected for upload, if MOSAIC_ENABLED is true, we'll have a checkbox "Mosaic" (just like the "Time" checkbox for vector layers) to request that the flow for the mosaic handling should be started.

If the checkbox "Mosaic" is checked, once the data upload is completed, the user will be asked if the uploaded file is a granule belonging to an existent Mosaic, or if a new Mosaic should be created.

We have 2 different flows:

• the user just uploaded the first granule for a brand new imagemosaic layer:
  1. upload the geotiff file.
  2. ask if the file represents a granule for a brand new mosaic (yes).
  3. 1. create the mosaic (setup the dimensions).
  4. setup the granule (assign values to the dimensions).
  5. setup and ingestion in geoserver.
• the uploaded file is a new granule to add to an existing imagemosaic layer:
  1. upload the geotiff file
  2. ask if the file represents a granule for a brand new mosaic (no)
  3. 2. choose an existing imagemosaic layer in geonode
  4. setup the granule (assign values to the dimensions)
  5. setup and ingestion in geoserver

When creating the mosaic, the user should give information about the associated dimensions, if any.

GeoServer uses a quite complex set of files to determine how to retrieve the custom dimensions, extracting them from the granule file name. We want GeoNode to create automatically these files for the users. Setting up these information is anyway quite complex, so the first proposed implementation will offer only a limited choice of additional dimensions: the user will be able to add up to:

• 2 time dimensions
• 1 spatial dimension (elevation).

The combinations of this dimension set should anyway cover a great number of use cases.

The user will be able to choose one of these format for each of the time dimension:

• year
• year + month
• year + month + day
• year + month + day + hour + minute + second

The elevation will always be parsed as a decimal number.

Once the mosaic is created, the user will be redirected to a page to enter the dimension values of the granule just uploaded.

If the mosaic has one or more dimensions, the user will have to insert in the GUI the related values for each of them. GeoNode should already know about the number and the format of the associated dimensions, so the input form should be built appropriately.

We may introduce here a bit of heuristic to find out if the file name of the uploaded file already brings any information about the dimensions, and pre-fill the GUI fields with them.

As said, GeoServer parse the granule file name to retrieve the dimension values. By limiting the dimension set, and by requesting to edit the dimension values in the UI, we are relieving the users from the burden of setting up and testing the regular expressions needed for parsing the input files names.

This stage receives as input the granule file, the dimensions description, the dimension values and a reference to the imagemosaic layer. The logic will format the filename according to what GeoServer is expecting, and will make the proper calls to the GeoServer importer module (that's why the importer backend should be set in the configuration).

The importer module has received many improvements in GeoServer 2.7 (see http://docs.geoserver.org/stable/en/user/extensions/importer/rest_examples.html#adding-a-new-granule-into-an-existing-mosaic), so we're going to leverage on these new features, such as image preprocessing.

The "Update Layer" dialog will have the options "Manage granules" and "Delete".

The "Delete" button will maintain the same semantic as for the other objects, and will remove the whole imagemosaic Layer.

The "Manage granules" button will display a page containing a list of all the granules of the mosaic, where the single granules can be removed from the mosaic.

In order to update a single granule, the user have to delete it from this list, and then run the whole upload procedure.

GeoServer 2.7.x implements improved functionalities to deal with mosaics. This proposal depends on the migration to GeoServer 2.7 (See https://github.com/GeoNode/geonodeissues/2040).

The described flows only explain how to add granules one by one. In the future we may want to enable to user to upload and ingest a batch of granules.

The imagemosaic module in GeoServer can work with several types of raster formats. For the sake of semplicity of the first implementation, only GeoTIFF will be supported initially.

Preprocessing on GeoServer side may be made optional, in case the provided GeoTIFF are just ready to be published.

This module should provide its own unit tests, and any integration tests should be added to maintain or increase coverage as necessary.

See the discussion on the geonode-dev list here:

http://lists.osgeo.org/pipermail/geonode-devel/2015-July/000162.html

N/A