Special and Temporal Extents
From Earth Science Information Partners (ESIP)
The Extent Spiral defines the spatial and temporal extent of the dataset. This information can be displayed on maps, profiles and timelines and used in spatial and temporal searches. Most documentation dialects include this information because it is so important to data discovery.
ISO Dialects
The ISO standard supports the definition of multiple extents for each dataset/service. In order to simplify the process of identifying the bounding extent, it is recommended that the id attribute be set = "boundingExtent" (see ISO Extents).
NASA GCMD Directory Interchange Format
The DIF format assumes that place keywords come from the GCMD Location Keywords.
netCDF
Extent information is included in the Attribute Conventions for Data Discovery and ctCDF files as global attributes:
<attribute name="geospatial_lat_max" value="90.0 " type="double"/> <attribute name="geospatial_lat_min" value="-90.0 " type="double"/> <attribute name="geospatial_lat_resolution" value="0.0416 " type="double"/> <attribute name="geospatial_lat_units" value="degrees_north"/> <attribute name="geospatial_lon_max" value="360.0 " type="double"/> <attribute name="geospatial_lon_min" value="0.0 " type="double"/> <attribute name="geospatial_lon_resolution" value="0.0416 " type="double"/> <attribute name="geospatial_lon_units" value="degrees_east"/> <attribute name="geospatial_vertical_max" value="0.0 " type="double"/> <attribute name="geospatial_vertical_min" value="0.0 " type="double"/> <attribute name="geospatial_vertical_positive" value="up"/> <attribute name="geospatial_vertical_units" value="m"/>
Many of the attributes included in this spiral can be calculated from the data using standard netCDF Tools if the file is compliant with the NetCDF Climate and Forecast (CF) Metadata Convention. In ncISO these attributes are given as part of the CFMetadata group:
<group name="CFMetadata">
<attribute name="geospatial_lon_min" value="-180.0" type="float" />
<attribute name="geospatial_lat_min" value="-80.0" type="float" />
<attribute name="geospatial_lon_max" value="179.5" type="float" />
<attribute name="geospatial_lat_max" value="85.0" type="float" />
<attribute name="geospatial_lon_units" value="degrees_east" />
<attribute name="geospatial_lat_units" value="degrees_north" />
<attribute name="geospatial_lon_resolution" value="0.5" />
<attribute name="geospatial_lat_resolution" value="0.5" />
<attribute name="time_coverage_start" value="2010-05-29T22:00:00Z" />
<attribute name="time_coverage_end" value="2011-05-21T20:00:00Z" />
<attribute name="time_coverage_units" value="seconds" />
<attribute name="time_coverage_resolution" value="314669.0" />
<attribute name="time_coverage_duration" value="P0Y0M356DT22H0M0.000S" />
</group>
THREDDS
The THREDDS dialect defines spatial ranges using start, size, resolution, and units and includes place keywords with vocabulary names.
<geospatialCoverage zpositive="down">
<northsouth>
<start>10</start>
<size>80</size>
<resolution>2</resolution>
<units>degrees_north</units>
</northsouth>
<eastwest>
<start>-130</start>
<size>260</size>
<resolution>2</resolution>
<units>degrees_east</units>
</eastwest>
<updown>
<start>0</start>
<size>22</size>
<resolution>0.5</resolution>
<units>km</units>
</updown>
<name vocabulary="GCMD Location Keywords">Arctic Ocean</name>
</geospatialCoverage>
Crosswalks
| Concept | Description | Paths |
|---|---|---|
| Southernmost Latitude | The southernmost latitude of the bounding rectangle. Note: OGC-SOS offering lists may not include the entire dataset. A gml:id attribute can be used to identify the bounding offering. |
OGC-SOS /sos:Capabilities/sos:Contents/sos:ObservationOfferingList/sos:ObservationOffering/gml:boundedBy/gml:Envelope/gml:lowerCorner ISO /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:geographicElement/gmd:EX_GeographicBoundingBox/gmd:southBoundLatitude/gco:Decimal THREDDS /thredds:catalog/thredds:metadata/thredds:geospatialCoverage/thredds:northsouth/thredds:start THREDDS /thredds:catalog/thredds:dataset/thredds:geospatialCoverage/thredds:northsouth/thredds:start netCDF /nc:netcdf/nc:CFMetadata/nc:attribute[@name=geospatial_lat_min] |
| Northernmost Latitude | The northernmost latitude of the bounding rectangle. Note: OGC-SOS offering lists may not include the entire dataset. A gml:id attribute (e.g. gml:id="network-all") can be used to identify the bounding offering. |
OGC-SOS /sos:Capabilities/sos:Contents/sos:ObservationOfferingList/sos:ObservationOffering/gml:boundedBy/gml:Envelope/gml:upperCorner ISO /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:geographicElement/gmd:EX_GeographicBoundingBox/gmd:northBoundLatitude/gco:Decimal netCDF /nc:netcdf/nc:CFMetadata/nc:attribute[@name=geospatial_lat_max] |
| Westernmost Longitude | The westernmost longitude of the bounding rectangle. Note: OGC-SOS offering lists may not include the entire dataset. A gml:id attribute can be used to identify the bounding offering. |
OGC-SOS /sos:Capabilities/sos:Contents/sos:ObservationOfferingList/sos:ObservationOffering/gml:boundedBy/gml:Envelope/gml:lowerCorner ISO /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:geographicElement/gmd:EX_GeographicBoundingBox/gmd:westBoundLongitude/gco:Decimal THREDDS /thredds:catalog/thredds:metadata/thredds:geospatialCoverage/thredds:eastwest/thredds:start THREDDS /thredds:catalog/thredds:dataset/thredds:geospatialCoverage/thredds:eastwest/thredds:start netCDF /nc:netcdf/nc:CFMetadata/nc:attribute[@name=geospatial_lon_min] |
| Easternmost Longitude | The westernmost longitude of the bounding rectangle. Note: OGC-SOS offering lists may not include the entire dataset. A gml:id attribute can be used to identify the bounding offering. |
OGC-SOS /sos:Capabilities/sos:Contents/sos:ObservationOfferingList/sos:ObservationOffering/gml:boundedBy/gml:Envelope/gml:upperCorner ISO /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:geographicElement/gmd:EX_GeographicBoundingBox/gmd:eastBoundLongitude/gco:Decimal netCDF /nc:netcdf/nc:CFMetadata/nc:attribute[@name=geospatial_lon_max] |
| Start Time | The start of the bounding time period | OGC-SOS /sos:Capabilities/sos:Contents/sos:ObservationOfferingList/sos:ObservationOffering/sos:time/gml:TimePeriod/gml:beginPosition ISO /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:temporalElement/gmd:EX_TemporalExtent/gmd:extent/gml:TimePeriod/gml:beginPosition THREDDS /thredds:catalog/thredds:dataset/thredds:timeCoverage/thredds:start THREDDS /thredds:catalog/thredds:metadata/thredds:timeCoverage/thredds:start netCDF /nc:netcdf/nc:CFMetadata/nc:attribute[@name=time_coverage_start] |
| End Time | The end of the bounding time period | OGC-SOS /sos:Capabilities/sos:Contents/sos:ObservationOfferingList/sos:ObservationOffering/sos:time/gml:TimePeriod/gml:endPosition ISO /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:temporalElement/gmd:EX_TemporalExtent/gmd:extent/gml:TimePeriod/gml:endPosition THREDDS /thredds:catalog/thredds:dataset/thredds:timeCoverage/thredds:end THREDDS /thredds:catalog/thredds:metadata/thredds:timeCoverage/thredds:end netCDF /nc:netcdf/nc:CFMetadata/nc:attribute[@name=time_coverage_end] |
| Vertical Minimum | The minimum height of the bounding rectangle | ISO /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:verticalElement/gmd:EX_VerticalExtent/gmd:minimumValue/gco:Real THREDDS /thredds:catalog/thredds:metadata/thredds:geospatialCoverage/thredds:updown/thredds:start THREDDS /thredds:catalog/thredds:dataset/thredds:geospatialCoverage/thredds:updown/thredds:start netCDF /nc:netcdf/nc:attribute[@name=geospatial_vertical_min] |
| Vertical Maximum | The maximum height of the bounding rectangle | ISO /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:verticalElement/gmd:EX_VerticalExtent/gmd:maximumValue/gco:Real netCDF /nc:netcdf/nc:attribute[@name=geospatial_vertical_max] |
| Place Keyword | A comma separated list of key words and phrases that give the location of the resource. Note: Some dialects include keywords, but they do not include mechanisms for identifying the type. In those cases it is difficult to unambiguously identify place keywords. |
ISO /*/gmd:identificationInfo/*/gmd:descriptiveKeywords/gmd:MD_Keywords[gmd:type/gmd:MD_KeywordTypeCode='place']/gmd:keyword/gco:CharacterString THREDDS /thredds:catalog/thredds:dataset/thredds:geospatialCoverage/thredds:name |
| Place Keyword Vocabulary | If you are following a guideline for the place words/phrases in your "keywords" attribute, put the name of that guideline here. | ISO /*/gmd:identificationInfo/*/gmd:descriptiveKeywords/gmd:MD_Keywords[gmd:type/gmd:MD_KeywordTypeCode='place']/gmd:thesaurusName/gmd:CI_Citation/gmd:title/gco:CharacterString THREDDS /thredds:catalog/thredds:dataset/thredds:geospatialCoverage/thredds:name/@thredds:vocabulary |
xPath Note: The xPaths included in this table use several wildcards. // means any path, so //gmd:CI_ResponsibleParty indicates a gmd:CI_ResponsibleParty anywhere in an XML file. /*/ indicates a single level with several possible elements. This usually indicates one of several concrete realizations of an abstract object. For example /*/gmd:identificationInfo could be gmd:MD_Metadata/gmd:identificationInfo or gmi:MI_Metadata/gmd:identificationInfo and gmd:identificationInfo//*/gmd:descriptiveKeywords could be gmd:identificationInfo/gmd:MD_DataIdentification/gmd:descriptiveKeywords or gmd:identificationInfo/srv:SV_ServiceIdentification/gmd:descriptiveKeywords.
