Navigating the Network: Part 2

Feature Level Metadata


What is Feature Level Metadata?


Step 1  Open ArcMap


Add All features and tables in the 0505 file gdb.


Collapse all layers in the table of contents and make sure you are on the “Source” tab.  

NHD FGDC compliant metadata is stored in a Metadata table contained within the database. This table is included in all NHD Downloads. NHD Databases have relationships built in between the tables that relate the features to the Metadata by the Perm_ID field. There are three tables that are used to discover NHD Feature Level Metadata: A feature table (NHDFlowline, NHDWaterbody, etc), NHDFeature to Metadata, and NHDMetadata.


Step 2 Open the NHDFlowline table


Right Click on the NHDFlowline layer and choose “Open Attribute Table”


The Permanent_Identifier field is the field used to associate a feature with its metadata.

Note that some Permanent Identifiers are short. These are grandfathered in from an older data model that contained a field known as Com_Id. As these features are updated these shorter perm ids will be replaced by the standard 36 character strings.  


What is a Permanent Identifier?


Step 3 Open the NHDFeatureToMetadata table


Right-click on the NHDFeatureToMetadata table and choose “Open”.


This table is used to build a relationship between the permanent_identifier field in the NHDFlowline attribute table and the Meta_ProcessID.


Step 4 Open the NHDMetadata table


Right-click on the NHDMetadata table and choose “Open”.

This table contains all metadata information for the features found in this dataset.


What information is contained in the NHDMetadata table?


Step 5 Relate a Feature to its Metadata


NHD Databases have relationships built between the three tables explored in steps 2-5. These relationships enable the user to relate features to their metadata.


Open the NHDFlowline Attribute Table.



In the upper left-hand corner of the table, click on the options menu   and then choose the option to select by attributes.


Enter this query in the space provided: "Permanent_Identifier" ='75431675'


A Flowline Feature with the name Kanawha River will be selected.


Next, we will see all metadata records associated with this feature.

Click on the Options menu    of the attribute table.


In the drop down menu, Choose “Related Tables”, then click on

NHDFlowlinetoMeta : 1DFToFeaturetoMetadata. '


The NHDFeaturetoMetadata table will appear with two Meta_ProcessID records that are related to the Kanawha River feature we selected previously.  

Next, we need to relate this table to the NHDMetadata table.


Click on the Options menu   of the attribute table.


Choose the option for “Joins and Relates”. Then Choose “Relate”.


Relate the NHDFeatureToMetadata table to the NHDMetadata table by the Meta_ProcessID and name the relate “Kanawha Metadata”.


Click “Ok”.


Click on the Options menu     of the attribute table.


Choose “Related Tables” from the dropdown menu.


Click on “Kanawha Metadata : NHDMetadata. This relate should be at the bottom of the dropdown menu.


The Metadata table will open with all fields related to this feature selected.


It is helpful to copy some of the fields with longer descriptions into another document to more easily read them.


The process last completed on this feature is here.


Why are some of the fiends in the metadata table left blank?


Step 7 Relate Metadata to its Feature


Just like features can be related to their metadata records, we can use an inverse approach to relate metadata records to the features associated with them.


In this exercise, we want to select all features that have been edited on April 18th, 2002 in order to have “Added flow relationships between subbasins and other updates as appropriate” according to the ProcessDescription field in the metadata table.  

Right-click on the NHDMetadata table and choose “Open”.


Make sure you are viewing all records, not just selected records. If any records are selected, clear your selection.   


Click on the Options menu     of the attribute table.


Choose “Select by Attributes”.


We will create a query to select the MetaProcess ID related to this process description.

Enter the following query:


"Meta_ProcessID" ='27210'


The correct Metadata record is now selected.


Next, we will relate this record, to it’s associated record(s) in the NHDFeaturetoMetadata table.


This relationship is built into the database.


Click on the Options menu of the NHDMetadata table.


Choose “Related Tables” from the dropdown menu, then select the relationship

 “NHDMetatoFeature : MToFeatureToMetadata”.


The NHDFeatureToMetadata table will appear with the associated record selected.


Next, we will relate this record to it’s associated features.


Click on the Options menu     of the NHDFeatureToMetadata table.


Choose “Related Tables” from the dropdown menu, then select the relationship



The feature associated with this metadata record is now selected in the NHDFlowline attribute table.


Right click on the selected field and select “Zoom to Layer”.  


You will now be taken to the updated feature.