Module: PostgisFunctions::LineStringFunctions

Defined in:
lib/postgis_functions/common.rb

Overview

LINESTRING

Instance Method Summary collapse

Instance Method Details

#crosses?(other) ⇒ Boolean

Takes two geometry objects and returns TRUE if their intersection “spatially cross”, that is, the geometries have some, but not all interior points in common. The intersection of the interiors of the geometries must not be the empty set and must have a dimensionality less than the the maximum dimension of the two input geometries. Additionally, the intersection of the two geometries must not equal either of the source geometries. Otherwise, it returns FALSE.

Returns Boolean ST_Crosses(geometry g1, geometry g2);

Returns:

  • (Boolean) 


605
606
607
 
# File 'lib/postgis_functions/common.rb', line 605

def crosses? other
  postgis_calculate(:crosses, [self, other])
end

#end_point ⇒ Object

Returns geometry end point.



589
590
591
 
# File 'lib/postgis_functions/common.rb', line 589

def end_point
  postgis_calculate(:endpoint, self)
end

#interpolate_point(fraction) ⇒ Object

Returns a point interpolated along a line. First argument must be a LINESTRING. Second argument is a float8 between 0 and 1 representing fraction of total linestring length the point has to be located.

See ST_Line_Locate_Point for computing the line location nearest to a Point.

Returns geometry ST_Line_Interpolate_Point(geometry a_linestring, float a_fraction);



666
667
668
 
# File 'lib/postgis_functions/common.rb', line 666

def interpolate_point(fraction)
  postgis_calculate(:line_interpolate_point, self, fraction)
end

#length ⇒ Object

Returns the 2D length of the geometry if it is a linestring, multilinestring, ST_Curve, ST_MultiCurve. 0 is returned for areal geometries. For areal geometries use ‘perimeter’. Measurements are in the units of the spatial reference system of the geometry.

Returns Float



533
534
535
 
# File 'lib/postgis_functions/common.rb', line 533

def length
  postgis_calculate(:length, self).to_f
end

#length_3d ⇒ Object

Returns the 3-dimensional or 2-dimensional length of the geometry if it is a linestring or multi-linestring. For 2-d lines it will just return the 2-d length (same as ‘length’)

Returns Float



544
545
546
 
# File 'lib/postgis_functions/common.rb', line 544

def length_3d
  postgis_calculate(:length3d, self).to_f
end

#length_spheroid(spheroid = EARTH_SPHEROID) ⇒ Object

Calculates the length 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 ellipsoid is a separate database type and can be constructed as follows:

SPHEROID[<NAME>,<SEMI-MAJOR AXIS>,<INVERSE FLATTENING>]

Example:

SPHEROID["GRS_1980",6378137,298.257222101]

Defaults to:

SPHEROID["IERS_2003",6378136.6,298.25642]

Returns Float length_spheroid(geometry linestring, spheroid);



565
566
567
 
# File 'lib/postgis_functions/common.rb', line 565

def length_spheroid(spheroid = EARTH_SPHEROID)
  postgis_calculate(:length_spheroid, self, spheroid).to_f
end

#line_crossing_direction(other) ⇒ Object

Warning: PostGIS 1.4+

Return crossing direction



613
614
615
 
# File 'lib/postgis_functions/common.rb', line 613

def line_crossing_direction(other)
  postgis_calculate(:lineCrossingDirection, [self, other])
end

#line_merge ⇒ Object

Returns a (set of) LineString(s) formed by sewing together a MULTILINESTRING.

Only use with MULTILINESTRING/LINESTRINGs. If you feed a polygon or geometry collection into this function, it will return an empty GEOMETRYCOLLECTION

Returns geometry ST_LineMerge(geometry amultilinestring);



701
702
703
 
# File 'lib/postgis_functions/common.rb', line 701

def line_merge
  postgis_calculate(:LineMerge, self, { :stcollect => self})
end

#line_substring(s, e) ⇒ Object

Return a linestring being a substring of the input one starting and ending at the given fractions of total 2d length. Second and third arguments are float8 values between 0 and 1. This only works with LINESTRINGs. To use with contiguous MULTILINESTRINGs use in conjunction with ST_LineMerge.

If ‘start’ and ‘end’ have the same value this is equivalent to ‘interpolate_point’.

See ‘locate_point’ for computing the line location nearest to a Point.

Returns geometry ST_Line_Substring(geometry a_linestring, float startfraction, float endfraction);



682
683
684
 
# File 'lib/postgis_functions/common.rb', line 682

def line_substring(s,e)
  postgis_calculate(:line_substring, self, [s, e])
end

#locate_along_measure(measure) ⇒ Object

Return a derived geometry collection value with elements that match the specified measure. Polygonal elements are not supported.

Semantic is specified by: ISO/IEC CD 13249-3:200x(E) - Text for Continuation CD Editing Meeting

Returns geometry ST_Locate_Along_Measure(geometry ageom_with_measure, float a_measure);



641
642
643
 
# File 'lib/postgis_functions/common.rb', line 641

def locate_along_measure(measure)
  postgis_calculate(:locate_along_measure, self, measure)
end

#locate_between_measures(a, b) ⇒ Object

Return a derived geometry collection value with elements that match the specified range of measures inclusively. Polygonal elements are not supported.

Semantic is specified by: ISO/IEC CD 13249-3:200x(E) - Text for Continuation CD Editing Meeting

Returns geometry ST_Locate_Between_Measures(geometry geomA, float measure_start, float measure_end);



653
654
655
 
# File 'lib/postgis_functions/common.rb', line 653

def locate_between_measures(a, b)
  postgis_calculate(:locate_between_measures, self, [a,b])
end

#locate_point(point) ⇒ Object

Returns a float between 0 and 1 representing the location of the closest point on LineString to the given Point, as a fraction of total 2d line length.

You can use the returned location to extract a Point (ST_Line_Interpolate_Point) or a substring (ST_Line_Substring).

This is useful for approximating numbers of addresses.

Returns float (0 to 1) ST_Line_Locate_Point(geometry a_linestring, geometry a_point);



628
629
630
 
# File 'lib/postgis_functions/common.rb', line 628

def locate_point point
  postgis_calculate(:line_locate_point, [self, point]).to_f
end

#num_points ⇒ Object

Return the number of points of the geometry. PostGis ST_NumPoints does not work as nov/08

Returns Integer ST_NPoints(geometry g1);



575
576
577
 
# File 'lib/postgis_functions/common.rb', line 575

def num_points
  postgis_calculate(:npoints, self).to_i
end

#start_point ⇒ Object

Returns geometry start point.



582
583
584
 
# File 'lib/postgis_functions/common.rb', line 582

def start_point
  postgis_calculate(:startpoint, self)
end