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Data Download

Note: This feature uses the Common Metadata Repository (CMR) and does not work for data sets stored elsewhere.

Each layer in Worldview can be mapped to a data product in the CMR. In the layer configuration, use the product attribute and provide the identifier for the downloadable product.

Each product is defined in the products section, keyed by identifier:

{
  "products": {
    "MYD04_L2": {
      "name": "MODIS/Aqua Aerosol 5-Min L2 Swath 10km",
      "handler": "AquaSwathMultiDay",
      "query": {
        "shortName": "MYD04_L2"
      },
      "nrt": {
        "by": "value",
        "field": "data_center",
        "value": "LANCEMODIS"
      },
      "urs": {
        "by": "value",
        "field": "data_center",
        "value": "LANCEMODIS"
      }
    }
  }
}

Handlers

Each product is assigned a handler that filters and processes the results from the CMR. The following handlers are available:

  • AquaSwathMultiDay: Use for Aqua 5-minute data granules where today, yesterday, and tomorrow appear together on the same map.
  • CollectionList: Does not display any information on the map and presents a list. Use this for collections that do not have granules and only have a collection level entry.
  • CollectionMix: Handles layers which only have collection-level metadata and have different collections based on the selected date. Uses "science" and "nrt" query flags to distinguish between "old" and "new" collections, respectively.
  • DailyAMSRE: Displays a single entry for a daily AMSR-E product. Since the metadata is too exact, this omits granules that happen to contain a small fraction of the day.
  • DailyGranuleList: Similar to List but also obtains granules three hours from yesterday and tomorrow. This handler is only used for MODIS Combined Value Added AOD and granules appear to be in six hour chunks. It isn't apparent why this handler was necessary.
  • HalfOrbit: Handles large granules that are broken up into an ascending and descending component.
  • List: Displays all granules for the given day listed in a dialog box and not displayed on the map.
  • MODISGrid: Maps MODIS H and V tiles to the sinusoidal grid.
  • MODISMix: Handles layers where near-real time data is blocked into five minute granules and where processed data is blocked into H and V sinusoidal grid tiles.
  • MODISSwath: Use for 5-minute data granules where only today is shown on the map.
  • TerraSwathMultiDay: Use for Terra 5-minute data granules where today, yesterday, and tomorrow appear together on the same map.
  • WELDGranuleFootprints: Use for the WELD product.

Query Parameters

The query configuration specifies the parameters sent in the CMR query. The available options are:

  • shortName: Short name used to identify this product. If more than one short name is required, for example, AIRIBRAD and AIRIBRAD_NRT, a list can be provided.
  • dataCenterId: Deprecated. Data center that provides this product. If more than one data center is required, for example, NSIDC_ECS and LANCEMODIS, a list can be provided. This parameter was used to speed up queries but now has the opposite effect and can break certain queries.
  • dayNightFlag: The value of the day/night flag, usually either DAY or NIGHT. Note that a granule that is both day and night is set to BOTH which isn't currently handled. Some products may populate this field with UNSPECIFIED
  • collection: Set to true when using the CollectionList handler for when no granules exist.

If two queries need to be executed to obtain NRT and non-NRT products when using the MODISMix handler, the query is specified in the following manner:

"query": {
  "science": {
    "shortName": "MYD09GA",
    "dataCenterId": "LPDAAC_ECS"
  },
  "nrt": {
    "shortName": "MYD09",
    "dataCenterId": "LANCEMODIS"
  }
}

Result Processing and Filtering

Each handler has a series of processors that change or filter each result. The result processors and configurations are as follows:

AntiMeridianMulti

If a granule splits the anti-meridian, this processor creates two polygons, one on each side of the map. The constructor takes a maxDistance argument that specifies a distance, in degrees. If a line segment in the polygon is greater than maxDistance, it's assumed to be crossing the anti-meridian.

CollectPreferred

If multiple granules exist for a given acquisition time, this attempts to group the granule as either near-real time or science quality. The granule should already be tagged for NRT before using this processor. One of the granules will be marked as preferred as indicated by the prefer variable in the data download model. Use PreferredFilter to select only one of these.

CollectVersions

If multiple granules exist for a given acquisition time, this attempts to group the granule by its version string. Use VersionFilter to select only one of these.

ConnectSwaths

Uses the acquisition times to create connector lines to show the swath ground track. Swaths are normally connected when the start time of one granule matches the end time of another granule. If this is not the case, use the delta parameter to specify, in seconds, how much time should be added to the start time to match the end time of another granule. For VIIRS, this is -60.

DateTimeLabel

Creates a label for this granule based on its acquisition date and time.

Densify

Not used at the moment.

DividePolygon

For polygons that cross the anti-meridian, normalize and create a mutli-polygon with a polygon on each side. Uses code provided by the Earthdata Search client.

ExtentFilter

Excludes granules that do not intersect the extent provided in the constructor.

GeometryFromCMR

Converts a CMR geometry to an OpenLayers 3 geometry.

GeometryFromMODISGrid

Creates a polygon footprint given a MODIS H and V tile number.

MODISGridIndex

Creates a index value by combining the MODIS H and V tile numbers.

MODISGridLabel

Creates a label for this granule based on the MODIS H and V tile numbers.

OfflineFilter

Filters out granules that are not available for download.

OrbitFilter

Filter by ascending or descending orbit. Configure with orbit with the following parameters:

  • type: Always regex_group
  • field: The field to inspect to find the orbit
  • regex: The regular expression to match against, should have one group.
  • match: Keep the granule if it matches this value.

Example:

"orbit": {
  "type": "regex_group",
  "field": "producer_granule_id",
  "regex": ".*([AD])\\.hdf$",
  "match": "A"
}

PreferredFilter

Only keeps near-real time granules if the prefer value passed in is nrt, otherwise keeps science-quality granules if science.

ProductLabel

Sets the label of the granule to the name provided in the constructor.

TagButtonScale

Sets a scale value for the granule selection buttons. Useful for making the buttons smaller for dense datasets. For example, WELD uses a value of 0.35.

TagList

Forces the results to display in a dialog box list instead of on the map.

TagNRT

Mark granules as near-real time depending on the following nrt configuration parameters:

  • by: Determine if this is NRT by value or regex
  • field: The field value to check against
  • value: Field value must equal this exactly.
  • regex: Field value must match this regular expression.
  • handler: If the handler for this product is MODISMix or CollectionMix, the handler to use for the NRT query, for example, TerraSwathMultiDay.

Example:

"nrt": {
  "handler": "TerraSwathMultiDay",
  "by": "value",
  "field": "data_center",
  "value": "LANCEMODIS"
},

TagProduct

Add a field to the granule result with the name of the product.

TagURS

Mark granules as requiring URS access depending on the following urs configuration parameters.

  • by: Determine if this requires URS by value, regex, or constant
  • field: The field value to check against
  • value: Field value must equal this exactly or the constant to set as.
  • regex: Field value must match this regular expression.

TagVersion

Parse out the version field into a numeric value that can used for comparison operations.

TagVersionRegex

Use a regular expression to parse out a version into a numeric value that can used for comparison operations. Parameters:

  • field: The name of the field that contains the version
  • namedRegex: Use MODISProducerGranuleID to parse out the version from a MODIS producer granule ID in the form of MOD04_L2.A2016137.2105.061.2017326151115.hdf
  • regex: If namedRegex is not used, a regular expression used to extract the version
  • parseVersion: Use MODIS to multiply version numbers below 10 by 10. This changes MODIS version numbers from 5, 51, 6, 61 to 50, 51, 60, 61.

TimeFilter

Keep granules that meet the following values passed into the spec constructor:

  • eastZone: Minutes since UTC midnight to check for granules from the previous day
  • westZone: Minutes since UTC midnight to check for granules from the next day.
  • maxDistance: Any line segment in a polygon that exceeds this distance, in degrees, is considered to have crossed the anti-meridian.

TimeLabel

Creates a label for this granule based on its acquisition time only. Times that are not from the selected day are indicated with + or - day indicators.

TitleLabel

Use the provided title in the metadata as the granule label.

Transform

Convert the EPSG:4326 coordinates into the other projections required for display.

VersionFilter

Given a set of granules with different versions, only select the latest.

VersionFilterExact

Only select granules with the exact version specified in the version configuration item.