Background (a bit of the business case for non his users..ignore if required ;-)
Statistical Agencies traditionally publish statistical data related to
statistical areas separately from the statistical boundaries that defines these
areas. This creates a significant barrier to the use of these data in general
mapping applications and more specialised spatial analysis systems.
To remove this barrier the Australian Bureau of Statistics (ABS) is evaluating
the use of GeoPackage as an output format for facilitating the publication of
both geospatial and statistical data. GeoPackage has a number of advantages one
of the most significant is the ability to define database views. A database
view is SQL statement that results in the creation of a “virtual” table that
can be The use of database views within the GeoPackage database container
provides a efficient mechanism to maintain the relationship (the relational
join) between the statistical boundaries (“geometries”) and the statistical
(“attribute") data.
By maintaining this relationship in a single published product this reduces the
barrier to their use in mapping applications, reduces the probability of
introduced error, increases the ease of use of statistical data in the
community.
The Problem...
QGIS is not seem to fully support database views in GeoPackage. In some
respects QGIS works as expected, but spatial and attribute selections and the
display of the attribute table produce incorrect results.
Example GeoPackage File:
SA1_BCP_B01_05.gpkg (134 MB)
<https://drive.google.com/open?id=0Bz44nz9iptC5NkF5WlpEZjBoSVk>https://drive.google.com/open?id=0Bz44nz9iptC5NkF5WlpEZjBoSVk
<https://drive.google.com/open?id=0Bz44nz9iptC5NkF5WlpEZjBoSVk>
Australian Bureau of Statistics 2011 Census Data
Product: Basic Community Profile. Statistical Tables B01 to B05
Images illustrating the issues
<https://drive.google.com/open?id=0Bz44nz9iptC5YjlrLV9vRFhmVE0>https://drive.google.com/open?id=0Bz44nz9iptC5YjlrLV9vRFhmVE0
<https://drive.google.com/open?id=0Bz44nz9iptC5YjlrLV9vRFhmVE0>
Things that work...
1. Views are identified as layers and can be loaded into the Layers Panel
2. Polygons are drawn as expected.
3. The Identify Feature tool can be used to highlight and individual polygon
and display the correct associated attribute data.
4. Styling and classification algorithms can be applied to compose correct
choropleth maps.
Things that do not work...
1. QGIS is not displaying the Attribute Table of a GeoPackage view correctly.
Attribute values are repeated for a single row.
2. Any Select operation that is applied either to the attributes or the
geometries results in the whole layer being selected.
In summary it looks like whilst the geometries of a GeoPackage view are being
interpreted correctly the link to the underlying attributes in a view is not.
Incidentally, neither the latest version of ArcGIS or MapInfo Profession can
interpret views in GeoPackage either and this has been identified as a bug by
both organisations.
Any help from some one who knows their way around how GeoPackage is
interpreting views would be gratefully received.
Marcus.
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