safety-screen/Nominatim
1
0
Fork 0
forked from hans/Nominatim
Code Pull Requests Activity

fix a number of corner cases with interpolation splitting

Browse Source 
Snapping a line to a point before splitting was meant to ensure
that the split point is really on the line. However, ST_Snap() does
not always behave well for this case. It may shorten the interpolation
line in some cases with the result that two points housenumbers
suddenly fall on the same point. It might also shorten the line down
to a single point which then makes ST_Split() crash.

Switch to a combination of ST_LineLocatePoint and ST_LineSubString
instead, which guarantees to keep the original geometry. Explicitly
handle the corner cases, where the split point falls on the beginning
or end of the line.
This commit is contained in:
Sarah Hoffmann
2023-04-06 16:54:00 +02:00
parent 5baa827b8a
commit ffe32af531
2 changed files with 93 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
lib-sql/functions/interpolation.sql
View File

@@ -164,7 +164,7 @@ DECLARE
newend INTEGER;
moddiff SMALLINT;
linegeo GEOMETRY;
splitline GEOMETRY;
splitpoint FLOAT;
sectiongeo GEOMETRY;
postcode TEXT;
stepmod SMALLINT;
@@ -223,15 +223,27 @@ BEGIN
FROM placex, generate_series(1, array_upper(waynodes, 1)) nodeidpos
WHERE osm_type = 'N' and osm_id = waynodes[nodeidpos]::BIGINT
and address is not NULL and address ? 'housenumber'
and ST_Distance(NEW.linegeo, geometry) < 0.0005
ORDER BY nodeidpos
LOOP
{% if debug %}RAISE WARNING 'processing point % (%)', nextnode.hnr, ST_AsText(nextnode.geometry);{% endif %}
IF linegeo is null THEN
linegeo := NEW.linegeo;
ELSE
splitline := ST_Split(ST_Snap(linegeo, nextnode.geometry, 0.0005), nextnode.geometry);
sectiongeo := ST_GeometryN(splitline, 1);
linegeo := ST_GeometryN(splitline, 2);
splitpoint := ST_LineLocatePoint(linegeo, nextnode.geometry);
IF splitpoint = 0 THEN
-- Corner case where the splitpoint falls on the first point
-- and thus would not return a geometry. Skip that section.
sectiongeo := NULL;
ELSEIF splitpoint = 1 THEN
-- Point is at the end of the line.
sectiongeo := linegeo;
linegeo := NULL;
ELSE
-- Split the line.
sectiongeo := ST_LineSubstring(linegeo, 0, splitpoint);
linegeo := ST_LineSubstring(linegeo, splitpoint, 1);
END IF;
END IF;
IF prevnode.hnr is not null
@@ -239,6 +251,9 @@ BEGIN
-- regularly mapped housenumbers.
-- (Conveniently also fails if one of the house numbers is not a number.)
and abs(prevnode.hnr - nextnode.hnr) > NEW.step
-- If the interpolation geometry is broken or two nodes are at the
-- same place, then splitting might produce a point. Ignore that.
and ST_GeometryType(sectiongeo) = 'ST_LineString'
THEN
IF prevnode.hnr < nextnode.hnr THEN
startnumber := prevnode.hnr;
@@ -300,12 +315,12 @@ BEGIN
NEW.address, postcode,
NEW.country_code, NEW.geometry_sector, 0);
END IF;
END IF;
-- early break if we are out of line string,
-- might happen when a line string loops back on itself
IF ST_GeometryType(linegeo) != 'ST_LineString' THEN
RETURN NEW;
END IF;
-- early break if we are out of line string,
-- might happen when a line string loops back on itself
IF linegeo is null or ST_GeometryType(linegeo) != 'ST_LineString' THEN
RETURN NEW;
END IF;
prevnode := nextnode;