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annotate schema/isrs_functions.sql @ 2431:48495bd3081d

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Construct stretch area between distance marks also from non-contiguous axis Before, both distance marks were required to be next to the same linestring of the waterway axis.
author Tom Gottfried <tom@intevation.de>
date Thu, 28 Feb 2019 19:44:38 +0100
parents 4c16f5ad1905
children 7677a2850a2d
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1 -- This is Free Software under GNU Affero General Public License v >= 3.0
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2 -- without warranty, see README.md and license for details.
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3
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4 -- SPDX-License-Identifier: AGPL-3.0-or-later
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5 -- License-Filename: LICENSES/AGPL-3.0.txt
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6
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7 -- Copyright (C) 2018, 2019 by via donau
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8 -- – Österreichische Wasserstraßen-Gesellschaft mbH
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9 -- Software engineering by Intevation GmbH
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10
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11 -- Author(s):
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12 -- * Tom Gottfried <tom@intevation.de>
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13 -- * Sascha Wilde <wilde@intevation.de>
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14
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15 -- Clip an area to a stretch given by a pair of ISRS location codes.
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16 -- Uses the table waterway.distance_marks_virtual to map ISRS location codes
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17 -- to their geo-location and the table waterway.waterway_axis to retrieve
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18 -- perpendicular direction at these geo-locations.
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19 -- Distance marks are assumed to be near the axis and the area passed as
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20 -- argument is assumed to intersect with the axis
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21 -- (use e.g. waterway area or fairway dimensions).
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22 -- If a multipolygon is passed, the union of the polygons intersecting with the
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23 -- relevant part of the axis is used for clipping.
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24 CREATE OR REPLACE FUNCTION ISRSrange_area(
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25 stretch isrsrange,
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26 area geometry
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27 ) RETURNS geometry
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28 AS $$
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29 WITH RECURSIVE
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30 -- Get coordinates of location codes
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31 points_geog AS (
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32 SELECT geom FROM waterway.distance_marks_virtual
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33 WHERE location_code = lower(stretch)
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34 OR location_code = upper(stretch)),
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35 utm_zone AS (
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36 -- Find best matchting UTM zone
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37 SELECT best_utm(ST_Collect(geom::geometry)) AS z
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38 FROM points_geog),
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39 axis AS (
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40 SELECT id, ST_Transform(wtwaxs::geometry, z) AS wtwaxs
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41 FROM waterway.waterway_axis, utm_zone),
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42 -- In order to guarantee the following ST_Covers to work,
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43 -- snap distance mark coordinates to axis
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44 points AS (
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45 SELECT ST_ClosestPoint(
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46 wtwaxs,
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47 ST_Transform(points_geog.geom::geometry, z)) AS geom
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48 FROM points_geog, utm_zone, (
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49 SELECT ST_Collect(wtwaxs) AS wtwaxs
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50 FROM axis) AS ax),
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51 axis_snapped AS (
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52 -- Iteratively connect non-contiguous axis chunks
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53 -- to find the contiguous axis on which given distance marks lie
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54 (SELECT ARRAY[id] AS ids, wtwaxs
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55 FROM axis, points
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56 WHERE ST_Intersects(
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57 ST_Buffer(axis.wtwaxs, 0.0001), points.geom)
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58 FETCH FIRST ROW ONLY)
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59 UNION
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60 -- Connect endpoint of next linestring with closest
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61 -- endpoint of merged linestring until a contiguous
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62 -- linestring connecting both distance marks is build up
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63 (SELECT refids || id,
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64 ST_LineMerge(ST_Collect(ARRAY(
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65 -- Linestring build up so far
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66 SELECT refgeom
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67 UNION
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68 -- Fill eventual gap
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69 SELECT ST_MakeLine(
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70 ST_ClosestPoint(
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71 ST_Boundary(refgeom), ST_Boundary(geom)),
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72 ST_ClosestPoint(
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73 ST_Boundary(geom), ST_Boundary(refgeom)))
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74 UNION
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75 -- Linestring to be added
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76 SELECT geom)))
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77 FROM axis_snapped AS axis_snapped (refids, refgeom),
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78 axis AS axis (id, geom),
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79 (SELECT ST_Collect(points.geom) AS pts
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80 FROM points) AS points
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81 WHERE id <> ALL(refids)
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82 AND NOT ST_Covers(ST_Buffer(refgeom, 0.0001), points.pts)
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83 ORDER BY ST_Distance(ST_Boundary(refgeom), ST_Boundary(geom))
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84 FETCH FIRST ROW ONLY)),
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85 axis_segment AS (
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86 -- Fetch end result from snapping
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87 SELECT wtwaxs AS line
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88 FROM axis_snapped
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89 WHERE array_length(ids, 1) = (
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90 SELECT max(array_length(ids, 1)) FROM axis_snapped)),
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91 axis_substring AS (
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92 -- Use linear referencing to clip axis between distance marks.
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93 -- Simplification is used to work-around the problem, that
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94 -- ST_LineSubstring might generate very small line segments at an
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95 -- end of the resulting linestring, that significantly differ from
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96 -- the direction of the input linestring due to finite precision
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97 -- of the calculation. The generated small segment of the
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98 -- resulting line leads to unexpected results of the buffer with
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99 -- endcap=flat in the CTE below.
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100 SELECT ST_SimplifyPreserveTopology(ST_LineSubstring(
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101 axis_segment.line, min(fractions.f), max(fractions.f)),
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102 0.0001) AS line
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103 FROM axis_segment, LATERAL (
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104 SELECT ST_LineLocatePoint(axis_segment.line, points.geom) AS f
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105 FROM points) AS fractions
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106 GROUP BY axis_segment.line),
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107 area_subset AS (
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108 -- In case area is a multipolygon, process the union of those
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109 -- polygons, which intersect with the axis. The union is to avoid
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110 -- problems with invalid/self-intersecting multipolygons
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111 SELECT ST_Union(a_dmp.geom) AS area
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112 FROM axis_substring, utm_zone, LATERAL (
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113 SELECT ST_MakeValid(ST_Transform(geom, z)) AS geom
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114 FROM ST_Dump(area)) AS a_dmp
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115 WHERE ST_Intersects(a_dmp.geom, axis_substring.line)
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116 ),
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117 rotated_ends AS (
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118 SELECT ST_Collect(ST_Scale(
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119 ST_Translate(e,
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120 (ST_X(p1) - ST_X(p2)) / 2,
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121 (ST_Y(p1) - ST_Y(p2)) / 2),
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122 ST_Point(d, d), p1)) AS blade
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123 FROM axis_substring, area_subset,
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124 LATERAL (SELECT i, ST_PointN(line, i) AS p1
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125 FROM (VALUES (1), (-1)) AS idx (i)) AS ep,
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126 ST_Rotate(ST_PointN(line, i*2), pi()/2, p1) AS ep2 (p2),
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127 ST_Makeline(p1, p2) AS e (e),
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128 LATERAL (SELECT (ST_MaxDistance(p1, area) / ST_Length(e))
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129 * 2) AS d (d)),
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130 range_area AS (
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131 -- Split area by orthogonal lines at the ends of the clipped axis
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132 SELECT (ST_Dump(ST_CollectionExtract(
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133 ST_Split(area, blade), 3))).geom
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134 FROM area_subset, rotated_ends)
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135 -- From the polygons returned by the last CTE, select only those
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136 -- around the clipped axis
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137 SELECT ST_Multi(ST_Transform(ST_Union(range_area.geom), ST_SRID(area)))
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138 FROM axis_substring, range_area
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139 WHERE ST_Intersects(ST_Buffer(range_area.geom, -0.0001),
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140 axis_substring.line)
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141 $$
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142 LANGUAGE sql;