@rdmr-eu/rdf-geopackage
v2.0.0
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Generate RDF out of a GeoPackage (for further processing)
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rdf-geopackage
Generate RDF out of a GeoPackage (for further processing)
Usage
Install using NPM locally npm install --global @rdmr-eu/rdf-geopackage
as a command line tool.
Check if it's installed correctly with rdf-geopackage --help
.
That should return the following help info:
Generate RDF from an OGC GeoPackage with rdf-geopackage
Options:
--help Show help [boolean]
--version Show version number [boolean]
-i, --input GeoPackage file [string]
-o, --output Output quads file [string]
--format Override output format (default: nquads)
[choices: "nq", "nquads", "trig", "nt", "ntriples", "ttl", "turtle"]
--bbox Limit features to bounding box [string]
--bbox-crs Coordinate Reference System code [string]
--only-layers Only output named feature layers and attribute ta
bles [array]
--include-binary-values Output binary values [boolean]
--base-iri Base IRI [string]
--model Data meta model [choices: "facade-x"]
--geosparql Output GeoSPARQL
[array] [choices: "wkt", "geojson", "bbox", "centroid", "length-area"] [defaul
t: ["wkt"]]
Options
Basic input and output serializations can be set with the following options:
--input
: the path to the input GeoPackage file (required). With-
, it reads the GeoPackage from stdin, e.g., piping a file with curl--output
: path to the file output. By default,rdf-geopackage
outputs nquads to stdout. Its extension sets the serialization format, optionally with.gz
to GZip the output. E.g.,--output myfile.ttl.gz
--format
: set the output format explicitly. Provide a file extension with.gz
to GZip the output.
Work with large GeoPackages by limiting the output features, output tables and binary values:
--bbox
limits the the output features to those in this area (default CRS: WGS84)--bbox-crs
indicates the CRS for the aforementioned bounding box. Supply a EPSG code (web lookup with EPSG.io) or a projection WKT.--only-layers
limits which feature layers (or attribute tables!) are output.--include-binary-values
overrides the default of skipping binary values. These will be base64 encoded string values with a^^xsd:base64Binary
data type. NULL values are never output.
Modify the model and types of the output triples or quads:
--base-iri
: set the relative base for the output RDF data. By default, this value is derived from the present working directory.--model
: the GeoPackage tables are not natively RDF data, so a module is programmed to generating triples according to a data meta-model. Included modules:- default:
facade-x
- default:
--geosparql
: modify which GeoSPARQL geometries, serializations and properties are output. Only the WKT literal is in layer native CRS, all other are calculated and/or projected. Multiple values (space separated) are allowed. Included feature predicates are listed in the table below.
| Option | GeoSPARQL feature predicates | Note |
| ------------------- | ----------------------------------------- | --------------------------------------------------------------- |
| wkt
(default) | geo:hasGeometry/geo:asWKT
| Output the feature's geometry as a WKT string literal |
| geojson
| geo:hasGeometry/geo:asGeoJSON
| Output the feature's geometry as a WGS84 GeoJSON string literal |
| bbox
| geo:hasBoundingBox
| Output a feature's bounding box |
| centroid
| geo:hasCentroid
| Output a feature's centroid point |
| length-area
| geo:hasMetricLength
geo:hasMetricArea
| Output the length (in m) and area (in m²) of the feature |
| always on | rdf:type geo:Feature
| Output the feature class |
RDF output
Model: Facade-X
Facade-X is a data meta-model from the SPARQL-Anything project, that can easily represent tabular data. Facade-X uses RDF containers and blank nodes to represent tables and rows. Column metadata is currently very limited (GH-24) and many values are not typed properly.
Features, geometries and CRS’s
Features and their geometries are represented using GeoSPARQL.
Only rows from feature tables are a geo:Feature
.
A feature has zero or more geometries predicated with geo:hasDefaultGeometry
.
There might be no geometry if the underlying library does not support the geometry type.
There may be multiple geometries if the feature is from a layer not in EPSG:4326.
That's because a GeoJSON serialization (geo:asGeoJSON
) is always (reprojected) in EPSG:4326.
A geo:Geometry
can be in only one CRS, meaning that when the feature is not originally in EPSG:4326, other serializations should also be reprojected.
That is undesirable, so in these cases, rdf-geopackage
generates a second geo:Geometry
for the WKT serialization (geo:asWKT
).
Example RDF output
Example data abridged from NGA:
the table media
is a feature table, nga_properties
is an attribute table.
prefix fx: <http://sparql.xyz/facade-x/ns/>
prefix geo: <http://www.opengis.net/ont/geosparql#>
prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
prefix xsd: <http://www.w3.org/2001/XMLSchema#>
prefix xyz: <http://sparql.xyz/facade-x/data/>
xyz:nga_properties { # representing a table
xyz:nga_properties a fx:root ; # representing a table
rdf:_1 [ # the first row
xyz:id 14;
xyz:property "subject";
xyz:value "Examples"
] .
}
xyz:media {
xyz:media a fx:root ;
rdf:_1 [
a geo:Feature ; # a row from a feature table
xyz:text "BIT Systems";
xyz:date "2023-01-23";
geo:hasDefaultGeometry [ # single geometry as CRS is EPSG:4326
a geo:Geometry ;
geo:asWKT "POINT (-104.801918 39.720014)"^^geo:wktLiteral ;
geo:asGeoJSON "{\"coordinates\":[-104.801918,39.720014],\"type\":\"Point\"}"^^geo:geoJSONLiteral
]
] .
}
Acknowledgements
This tool was developed for a project funded by the City Deal Openbare ruimte, executed by Stichting Kennisplatform CROW.