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https://issues.apache.org/jira/browse/SIS-187?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15045007#comment-15045007
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M. Le Bihan commented on SIS-187:
---------------------------------
I think we can see this subject more in detail when we will attempt to read a
.PRJ file.
I've found this example on the Internet, this is why I took the example of
_envelope.getLower("latitude")_ as it was the name of one axis in the following
.PRJ :
{code}GEODCRS["WGS 84",
DATUM["World Geodetic System 1984",
ELLIPSOID["WGS 84",6378137,298.257223563,LENGTHUNIT["metre",1.0]]],
CS[ellipsoidal,2],
AXIS["latitude",north,ORDER[1]],
AXIS["longitude",east,ORDER[2]],
ANGLEUNIT["degree",0.01745329252],
ID["EPSG",4326]]{code}
But I have not always this information. French metropolitan cities outlines has
this PRJ :
{code}PROJCS["RGF93_Lambert_93",
GEOGCS["GCS_RGF_1993",
DATUM["D_RGF_1993",SPHEROID["GRS_1980",6378137.0,298.257222101]
],
PRIMEM["Greenwich",0.0],
UNIT["Degree",0.0174532925199433]],
PROJECTION["Lambert_Conformal_Conic"],
PARAMETER["False_Easting",700000.0],
PARAMETER["False_Northing",6600000.0],
PARAMETER["Central_Meridian",3.0],
PARAMETER["Standard_Parallel_1",44.0],
PARAMETER["Standard_Parallel_2",49.0],
PARAMETER["Latitude_Of_Origin",46.5],
UNIT["Meter",1.0]
]{code}
where no axis are declared.
And Guadeloupean cities outlines have only a readme.txt file mentionning :
"_UTM Nord fuseau 20_"...
If you read a random shapefile from the Internet, and that you tell : "_I don't
trust that X, Y, Z axis given by getX...(), getY...(), getZ...() really
represent the X, Y, Z axis._"
Then you have to find a way from the .prj file to give the true axis that are
used, and not the ones you believe you should find.
In example : if a funny creator of shapefile has wished to use it's Z axis for
time (and had put an Axis label on it naming it "time"), you must not put a
direction on this axis designing EAST.or NORTH.
> Reduce visibility of Shapefile fields
> -------------------------------------
>
> Key: SIS-187
> URL: https://issues.apache.org/jira/browse/SIS-187
> Project: Spatial Information Systems
> Issue Type: Sub-task
> Components: Shapefile
> Reporter: Martin Desruisseaux
> Assignee: M. Le Bihan
> Labels: JDBC, Shapefile
> Fix For: 0.7
>
>
> The {{Shapefile}} implementation contains many fields, and all of them are
> currently public. Probably many of them could be private. Below is a list of
> fields with a guess of whether users are likely to want this information, and
> how he could obtain it.
> h3. Fields that could be considered internal mechanic
> * {{FileCode}}: currently used only in {{Shapefile.toString()}}
> implementation without explanation.
> * {{FileLength}}: currently used only in {{Shapefile.toString()}}
> implementation. Potentially useful to the {{Shapefile}} reader itself, but
> unlikely to be useful to external user since getting a useful meaning from a
> file length require knowledge of the file format structure.
> * {{Version}}: currently used only in {{Shapefile.toString()}}
> implementation. Not clear if it is the file format version or the dataset
> version. In the former case, this is an important information for the
> {{Shapefile}} reader but less for other users. In the later case, it could be
> an ISO metadata property.
> * {{dbf}}: a pointer to the underlying {{Database}} object. May be a
> dangerous things to expose. If nevertheless we really want to give direct
> access to the DBF database, maybe we should return a JDBC {{Connection}}
> instead.
> h3. Information to be made accessible through a public API
> * {{xmin}}, {{ymin}}, {{xmax}}, {{ymax}}: the spatial extent of the data.
> Could be made accessible through the ISO 19115 {{GeographicBoundingBox}}
> element. However it is unclear if those elements are always expressed in a
> geographic CRS or if they can be in a projected CRS.
> * {{zmin}}, {{zmax}}: the vertical extent of the data. Could be made
> accessible through the ISO 19115 {{VerticalExtent}} element. However the
> {{VerticalCRS}} of that extent is currently unknown.
> * {{main}}, {{mmax}}: the javadoc does not said what those values are.
> * {{FeatureMap}}: the set of {{Feature}} is indeed important, but maybe we
> should return them through some kind of iterator (or a JDK8 {{Stream}} ?) for
> fetching data on-demand (in a later implementation, not necessarily now)
> rather than loading all of them at {{Shapefile}} construction time.
> h3. Open questions
> * {{ShapeType}}: currently used only in {{Shapefile.toString()}}
> implementation. Tells whether the geometries are points, polygons, etc.
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