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OverlayNG and Invalid Geometry
A recent blog post by Elephant Tamer gives a critical appraisal of the improvements to overlay processing shipped in PostGIS 3.1 with GEOS 3.9. The author is disappointed that PostGIS still reports...
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JTS goes to Mars!
The other day this badge popped up on my GitHub profile:Sure enough, there is JTS in the list of dependencies provided by the Jet Propulsion Laboratory (JPL). So take that, Elon - JTS got there first!...
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Fixing Invalid Geometry with JTS
TLDR: JTS can now fix invalid geometry!The JTS Topology Suite implements the Geometry model defined in the OGC Simple Features specification. An important part of the specification is the definition...
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JTS IsSimple gets simpler (and faster)
Hard to believe that the JTS Topology Suite is almost 20 years old. That's 140 in dog years! Despite what they say about old dogs, one of the benefits of longevity is that you have the opportunity to...
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JTS IsValidOp Built Back Better
In a previous post I described how the JTS Topology Suite operation IsSimpleOp has been completely rewritten to reduce code dependencies, improve performance, and provide a simpler, more understandable...
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Query KD-trees 100x faster with this one weird trick!
Recently a GEOS patch was contributed to change the KdTree query implementation to use an explicit stack rather than recursion. This has been ported to JTS as PR #779 (along with some refactoring).The...
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JTS Polygon Triangulation, at last
A (long) while ago I posted about "soon-to-be-released" JTS code for polygon triangulation using Ear Clipping. It turned out it was actually in the category of "never-to-be-released". However, later...
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Christmas Wrapping
Every so often I produce an image in the JTS TestBuilder which strikes me as worthy of capture. Here's one that seems pretty seasonal:It is generated like this:Produce two sets of 1000 random points...
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JTS Offset Curves
Offset curves (also known as parallel curves) are an oft-requested feature in JTS. They are a natural extension to the concept of buffering, and are useful for things like placing labels along rivers....
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Concave Hulls in JTS
A common spatial need is to find a polygon that accurately represents a set of points. The convex hull of the points often does not provide this, since it can enclose large areas which contain no...
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Cubic Bezier Curves in JTS
As the title of this blog indicates, I'm a fan of linearity. But sometimes a little non-linearity makes things more interesting. A convenient way to generate non-linear curved lines is to use Bezier...
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Outer and Inner Concave Polygon Hulls in JTS
The JTS Topology Suite recently gained the ability to compute concave hulls. The Concave Hull algorithm computes a polygon enclosing a set of points using a parameter to determine the "tightness"....
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Using Outer Hulls for Smoothing Vectorized Polygons
The electrons were hardly dry on the JTS Outer and Inner Polygon Hull post when another interesting use case popped up on GIS StackExchange. The question was how to remove aliasing artifacts (AKA...
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Concave Hulls of Polygons
A common spatial need is to compute a polygon which contains another set of polygons. There are numerous use cases for this; for example:Generalizing groups of building outlines (questions: 1, 2)...
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Algorithm for Concave Hull of Polygons
The previous post introduced the new ConcaveHullOfPolygons class in the JTS Topology Suite. This allows computing a concave hull which is constrained by a set of polygonal geometries. This supports...
View ArticleJTS 1.19 Released
JTS 1.19 has just been released! There is a great deal of new, improved and fixed functionality in this release - see the GitHub release page or the Version History for full details.This blog has...
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Polygonal Coverages and Operations in JTS
An important concept in spatial data modelling is that of a coverage. A coverage models a two-dimensional region in which every point has a value out of a range (which may be defined over one or a set...
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Validating Polygonal Coverages in JTS
The previous post discussed polygonal coverages and outlined the plan to support them in the JTS Topology Suite. This post presents the first step of the plan: algorithms to validate polygonal...
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Relational Properties of DE-9IM spatial predicates
There is an elegant mathematical theory of binary relations. Homogeneous relations are an important subclass of binary relations in which both domains are the same. A homogeneous relation R is a...
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Alpha Shapes in JTS
Recently JTS gained the ability to compute Concave Hulls of point sets. The algorithm used is based the Chi-shapes approach described by Duckham et al. It works by eroding border triangles from the...
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Fast Coverage Union in JTS
The next operation delivered in the build-out of Simple Polygonal Coverages in the JTS Topology Suite is Coverage Union. This is simply the topological union of a set of polygons in a polygonal...
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Simplifying Polygonal Coverages with JTS
A new capability for the JTS Topology Suite is operations to process Simple Polygonal Coverages. A Simple Polygon Coverage is a set of edge-matched, non-overlapping polygonal geometries (which may be...
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JTS Topological Relationships - the Next Generation
The most fundamental and widely-used operations in the JTS Topology Suite are the ones that evaluate topological relationships between geometries. JTS implements the Dimensionally-Extended 9...
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RelateNG Performance
A previous post introduced a new algorithm in the JTS Topology Suite called RelateNG. It computes topological relationships between geometries using the Dimensionally-Extended 9 Intersection Model...
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Coverage Cleaning in JTS
The JTS Topology Suite has been rolling out the capability to manage polygonal coverages. It supports modelling polygonal coverages as arrays of discrete polygonal geometries. This is simple to work...
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