Center of Excellence for Geospatial Information Science (CEGIS)

Linked Geospatial Data System Architecture

A prototype system for managing, querying, and retrieveing data from The National Map in Resource Description Framework (RDF) is developed.  The objective of the system is to integrate cross-thematic geographic information system features from The National Map and to coreference data from various sources and formats.   

 

Basic concept for linked data system

High-level concept diagram for linked data system architecture prototype developed for data query and retrieval from The National Map

(Credit: Dalia Varanka. Public domain.)

 

The Map as Knowledge Base project is developing a prototype system for delivering data from The National Map as Linked Open Data (LOD). The user interface of this system engages various visualization methods for users to quary, evaluate, and retrieve data from the USGS and non-USGS sources. The core concept is that data would be co-referenced, displayed and available for further exploration. The UI supports the browseable graph approach for data queries that more specifically allows the user to limit data to their criteria and integrate with related data. 

 

Workflow diagram for linked data system

Workflow diagram for coreferencing linked data using prototype system

(Public domain.)

System Architecture

The general logical diagram of the system to execute the concept described aboce is shown below the high-level diagram in the workflow diagram.  The system modules are all free and open-source software.   

 

 

 

 

 

 

 

 

 

 

 

 

 

Image of the Map Knowledge Base query builder

View of a query builder application within the Map as Knowledge Base user interface

(Public domain.)

 

Data Visualization

Several starting points are possible for the Map as Knowledge Base user.  SPARQL or GeoSPARQL queries are assisted with a query builder. The image shown below assists the selection of a graph dataset, selection of properties, and filtering results, among other semi-automated functions.

The user interface lists datasets to select through a menu.

Image of the drop down data sets available in the Map Knowledge Base user interface

Image of data sets available to use in the interface of the Map Knowledge Base visualization system. 

(Public domain.)

When selcting a feature of interest, a pop-up window apears with property links, as shown in the image below.  An option to query more information returns additional properties.

Image of the popup window when selecting a feature in the Map Knowledge Base user interface

The selection of a feature to query results in a popup window with property links. An option for more information sends a query to retrieve additional properties.

(Public domain.)

In addition to map visualization an ontology can be viewed either as a separate window for full viewing, or a smaller inset view for focused on a feature of interest.

An example ontology visualization used within the Map as Knowledge Base user interface

View of a default ontology of the data graph being used in the Map as Knowledge Base user interface

(Public domain.)

Small view of the ontology as an insert in the main Map as Knowledge Base user interface

View of the default ontology of the data graph being used in the Map as Knowledge Base user interface

(Credit: Tanner Fry. Public domain.)

Converting Data from The National Map to Resource Description Framework (RDF)

This procedure converts data for the vector format themes of The National Map (Transportation, Government Boundaries,Structures, and Hydrography). These datasets typically take the form of Esri GDB (Geographic Data Base format). The goal is to convert them to XML / JSON. The procedure consists of three basic steps: Step 1: Retrieving data from Amazon S3, Step 2: Converting the retrieved GDB files to XML, Step 3: Converting XML files to required format (mostly JSON / JSON-LD). 

The files are compressed and can be download here TOPO Files.zip or from the tab below.