[PostGIS] #6077: Some notes about enhancements to the postgis manual

[PostGIS]

#6077: Some notes about enhancements to the postgis manual
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 Reporter:  jidanni        |      Owner:  robe
     Type:  enhancement    |     Status:  new
 Priority:  low            |  Milestone:  PostGIS 3.6.3
Component:  documentation  |    Version:  3.6.x
 Keywords:                 |
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 Hi. Here are some notes I made about enhancements for the postgis manual.
 I had better give them to you before even I no longer know what I was
 thinking.


 geometry CG_Visibility( geometry polygon, geometry point);
 geometry CG_Visibility( geometry polygon, geometry pointA, geometry
 pointB);
 point and segment missing in example images.

 The geometry dimension is a property of geometry types. Point types have
 dimension 0, linear types have dimension 1, and polygonal types have
 dimension 2. Collections have the dimension of the maximum element
 dimension.

 Mention what has dimensions 3 and 4 etc.!

 Geometries are topologically closed, so they always contain their
 boundary. The boundary is a geometry of dimension one less than that of
 the geometry itself.
 Give examples.

 The OGC geometry model defines validity rules for each geometry type.
 These rules ensure that geometry values represents realistic situations
 (e.g. it is possible to specify a polygon with a hole lying outside ITS
 xxxthe shell, but this makes no sense geometrically and is thus invalid).
 PostGIS also allows storing and manipulating invalid geometry values. This
 allows detecting and fixing them if needed. See Section 4.4, “Geometry
 Validation”


 A MultiPolygon is a collection of non-overlapping, non-adjacent Polygons.
 Polygons in the collection may touch only at a finite number of points.
 Explain adjacent vs. touching. Finite number? 17?  Wait, way down below
 this is explained. Add a link to that please. (That works offline.)


 A PolyhedralSurface is a contiguous collection of patches or facets which
 share some edges. Each patch is a planar Polygon. If the Polygon
 coordinates have Z ordinates then the surface is 3-dimensional. ADD PIC.
 Else too abstract.

   VALUES ( ST_GeomFromText('POINT(-126.4 45.32)', 312), 'A Place');
   Mention again that 312 is the SRID.

 The geometry data type is opaque, which means that all access is done via
 invoking functions on geometry values. Functions allow creating geometry
 objects, accessing or updating all internal fields, and compute new
 geometry values. COMPUTING.

 By default, all distance and area calculations are done on the spheroid.
 You should find that the results of calculations in local areas match up
 will with local planar results in good local projections. Over larger
 areas, the spheroidal calculations will be more accurate than any
 calculation done on a projected plane.
 OK, BUT REMIND what is the difference between the two.

 coord_dimension
 The coordinate dimension (2, 3 or 4) of the column.
 Mention why no 0 or 1.


 It may be required to identify all road segments that cross each other,
 not at a point, but in a line (perhaps to validate some business rule).
 BUSINESS RULE: like insurance policy no valid on two-way one lane roads?

 name                        | roads_km
 ----------------------------+------------------
 SURREY                      | 1539.47553551242
 Nanometers necessary here?

   SELEcT ST_AsText(geom)

 SELECT ST_AsText(ST_Letters('Yo'), 1); #The 1 overrides the font?

 Index is 1-based as for OGC specs since version 0.8.0. Backward indexing
 (negative index) is not in OGC[MISSING PERIOD] Previous versions
 implemented this as 0-based instead.

 SELECT ST_AsText(geom) as line, ST_AsText(ST_Reverse(geom)) As reverseline
 FROM
 (SELECT ST_MakeLine(ST_Point(1,2),
                 ST_Point(1,10)) As geom) as foo;

 FOO NEEDED?

 Find broadcasting towers that receiver with limited range can receive.
                               ^a

 EPSG:26986 is state plane Massachusetts meters[Period]

 float ST_Angle( geometry point1, geometry point2, geometry point3,
 geometry point4);
 float ST_Angle( geometry point1, geometry point2, geometry point3[,
 geometry point4]);

 .....
 ST_LengthSpheroid( geometry a_geometry, spheroid a_spheroid);

 Description
 Calculates the length or perimeter of a geometry on an ellipsoid. This is
 useful if the coordinates of the geometry are in longitude/latitude and a
 length is desired without reprojection. The spheroid is specified by a
 text value as follows:
 ..... s/ellipsoid/sphorid / or say why...

 float ST_MinimumClearance( geometry g);
 need pictures to explain better.

 Examples: 2.5Dish
 Note this is not a true intersection, compare to the same example using
 ST_3DIntersection.
 [No image provided: so Say if we are to imagine a 2.5 meter satellite dish
 or what.]

 ST_Node( geo ADD IMAGE.
 Thanks.
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/6077>
PostGIS <http://trac.osgeo.org/postgis/>
The PostGIS Trac is used for bug, enhancement & task tracking, a user and developer wiki, and a view into the subversion code repository of PostGIS project.