Documenting Spatial and Temporal Extents

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.

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	Dialect (Fit) Paths
Bounding Box	A bounding box for identifying a geographic area of interest Note: This concept is called "Coverage" in the CSW Specification	ISO /*/gmd:identificationInfo/gmd:MD_DataIdentification/gmd:extent/gmd:EX_Extent/gmd:geographicElement/gmd:EX_GeographicBoundingBox ISO /*/gmd:identificationInfo/srv:SV_ServiceIdentification/srv:extent/gmd:EX_Extent/gmd:geographicElement/gmd:EX_GeographicBoundingBox ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:geographicElement/gex:EX_GeographicBoundingBox ECHO /*/echo:Spatial/echo:HorizontalSpatialDomain/echo:Geometry/echo:BoundingRectangle DIF /dif:DIF/dif:Spatial_Coverage
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.	ISO (1) /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:geographicElement/gmd:EX_GeographicBoundingBox/gmd:southBoundLatitude/gco:Decimal ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:geographicElement/gex:EX_GeographicBoundingBox/gex:southBoundLatitude/gco:Decimal ECHO (1) /*/echo:Spatial/echo:HorizontalSpatialDomain/echo:Geometry/echo:BoundingRectangle/echo:SouthBoundingCoordinate DIF (1) /dif:DIF/dif:Spatial_Coverage/dif:Southernmost_Latitude
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.	ISO (1) /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:geographicElement/gmd:EX_GeographicBoundingBox/gmd:northBoundLatitude/gco:Decimal ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:geographicElement/gex:EX_GeographicBoundingBox/gex:northBoundLatitude/gco:Decimal ECHO (1) /*/echo:Spatial/echo:HorizontalSpatialDomain/echo:Geometry/echo:BoundingRectangle/echo:NorthBoundingCoordinate DIF (1) /dif:DIF/dif:Spatial_Coverage/dif:Northernmost_Latitude
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.	ISO (1) /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:geographicElement/gmd:EX_GeographicBoundingBox/gmd:westBoundLongitude/gco:Decimal ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:geographicElement/gex:EX_GeographicBoundingBox/gex:westBoundLongitude/gco:Decimal ECHO (1) /*/echo:Spatial/echo:HorizontalSpatialDomain/echo:Geometry/echo:BoundingRectangle/echo:WestBoundingCoordinate DIF (1) /dif:DIF/dif:Spatial_Coverage/dif:Westernmost_Longitude
Easternmost Longitude	The easternmost 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.	ISO (1) /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:geographicElement/gmd:EX_GeographicBoundingBox/gmd:eastBoundLongitude/gco:Decimal ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:geographicElement/gex:EX_GeographicBoundingBox/gex:eastBoundLongitude/gco:Decimal ECHO (1) /*/echo:Spatial/echo:HorizontalSpatialDomain/echo:Geometry/echo:BoundingRectangle/echo:WestBoundingCoordinate DIF (1) /dif:DIF/dif:Spatial_Coverage/dif:Easternmost_Longitude
Temporal Extent	The temporal extent of the resource	ISO /*/gmd:MD_DataIdentification/gmd:extent/gmd:EX_Extent/gmd:temporalElement/gmd:EX_TemporalExtent ISO-1 /*/mri:MD_DataIdentification/mri:extent/gex:EX_Extent/gex:temporalElement/gex:EX_TemporalExtent ECHO /*/Temporal/RangeDateTime DIF /dif:TemporalCoverage
Start Time	The start of the bounding time period	ISO /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:temporalElement/gmd:EX_TemporalExtent/gmd:extent/gml:TimePeriod/gml:beginPosition ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:temporalElement/gex:EX_TemporalExtent/gex:extent/gml:TimePeriod/gml:begin/gml:TimeInstant/gml:timePosition ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:temporalElement/gex:EX_TemporalExtent/gex:extent/gml:TimePeriod/gml:beginPosition ECHO /*/echo:Temporal/echo:RangeDateTime/echo:BeginningDateTime DIF /dif:DIF/dif:Temporal_Coverage/dif:Start_Date
End Time	The end of the bounding time period	ISO /*/gmd:identificationInfo/*/gmd:extent/gmd:EX_Extent/gmd:temporalElement/gmd:EX_TemporalExtent/gmd:extent/gml:TimePeriod/gml:endPosition ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:temporalElement/gex:EX_TemporalExtent/gex:extent/gml:TimePeriod/gml:end/gml:TimeInstant/gml:timePosition ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:temporalElement/gex:EX_TemporalExtent/gex:extent/gml:TimePeriod/gml:endPosition ECHO /*/echo:Temporal/echo:RangeDateTime/echo:EndingDateTime ECHO /*/echo:Temporal/echo:EndsAtPresentFlag DIF /dif:DIF/dif:Temporal_Coverage/dif:Stop_Date
Vertical Extent	The vertical extent of the resource	ISO /*/gmd:MD_DataIdentification/gmd:extent/gmd:EX_Extent/gmd:verticalElement/gmd:EX_VerticalExtent ISO-1 /*/mri:MD_DataIdentification/mri:extent/gex:EX_Extent/gex:verticalElement/gex:EX_VerticalExtent DIF /dif:SpatialCoverage
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 ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:verticalElement/gex:EX_VerticalExtent/gex:minimumValue/gco:Real DIF /dif:DIF/dif:Spatial_Coverage/dif:Minimum_Altitude DIF /dif:DIF/dif:Spatial_Coverage/dif:Minimum_Depth
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 ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:verticalElement/gex:EX_VerticalExtent/gex:maximumValue/gco:Real DIF /dif:DIF/dif:Spatial_Coverage/dif:Maximum_Altitude DIF /dif:DIF/dif:Spatial_Coverage/dif:Maximum_Depth
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 ISO /gmd:MD_Metadata/gmd:identificationInfo/gmd:MD_DataIdentification/gmd:extent/gmd:EX_Extent/gmd:geographicElement/gmd:EX_GeographicDescription/gmd:geographicIdentifier/gmd:MD_Identifier/gmd:code/gco:CharacterString ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:descriptiveKeywords/mri:MD_Keywords[mri:type/mri:MD_KeywordTypeCode='place']/mri:keyword/gco:CharacterString ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:geographicElement/gex:EX_GeographicDescription/gex:geographicIdentifier/mcc:MD_Identifier/mcc:code/gco:CharacterString DIF /dif:DIF/dif:Location/dif:Location_Category DIF /dif:DIF/dif:Location/dif:Location_Type DIF /dif:DIF/dif:Location/dif:Location_Subregion1 DIF /dif:DIF/dif:Location/dif:Location_Subregion2 DIF /dif:DIF/dif:Location/dif:Location_Subregion3 DIF /dif:DIF/dif:Location/dif:Detailed_Location
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 ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:descriptiveKeywords/mri:MD_Keywords[mri:type/mri:MD_KeywordTypeCode='place']/mri:thesaurusName/cit:CI_Citation/cit:title/gco:CharacterString ISO-1 /mdb:MD_Metadata/mdb:identificationInfo/*/mri:extent/gex:EX_Extent/gex:geographicElement/gex:EX_GeographicDescription/gex:geographicIdentifier/mcc:MD_Identifier/mcc:authority/cit:CI_Citation/cit:title/gco:CharacterString

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.

Section 3 - Metadata Implementation