Questions tagged [geometry]

(1) abstract geometry; (2) storing geographic data in projected coordinates; (3) a generic ESRI term for vector features; a class for "geometry" objects.

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2answers
149 views

MMP of geometries

MBR is used for extent of geometries.. then what is the use of MMP.. is it for visualization the objects?
22
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3answers
11k views

Seeking Generalisation Strategies for Building Outlines in PostGIS?

I have a dataset of building footprints vectorised from a raster dataset. The dataset is currently just a vector representation of the raster data. I would like a polygon dataset that only has ...
19
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2answers
8k views

Finding tunnel center line?

I have some map files consisting of 'polylines' (each line is just a list of vertices) representing tunnels, and I want to try and find the tunnel 'center line' (shown, roughly, in red below). I've ...
3
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1answer
787 views

Is it possible to figure out which “Path”(PointCollection) is clicked on within a PolyLine?

I am using ArcGIS WPF's Polyline to plot several lines (PointCollections). Adding a Path(PointCollection) looks something like this. PointCollection collection = new PointCollection(); PolyLine ...
13
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5answers
1k views

Simulating the expansion of polygon features

I've got what I'm hoping will be an interesting question. I'm working on an assignment for an intro to GIS course that uses some Gulf oil spill data to introduce common vector-based spatial analysis ...
4
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1answer
3k views

Clipping a SqlGeometry

I have been messing around with the SqlGeometry in the Microsoft.SqlServer.Types namespace in .NET, and have been rather impressed. Can anyone provide me with an example of how I could clip a ...
10
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2answers
430 views

Tools for importing historical maps into modern GIS systems?

What tools exist to derive geometries for use with modern GIS systems from older scanned maps? I am referring more to libraries that generate actual data rather than present an interface for ...
6
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1answer
2k views

Help simplifying multipolygons in geodjango

I have a few multipolygons that have several hundred points in them. I'm looking to create less complex "thumbnails" polygons. Naturally I'm attempting to use the simplify method, which is supposed ...
116
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13answers
47k views

What are Definition, Algorithms and Practical Solutions for Concave Hull? [closed]

Convex Hull A convex hull of a shape is defined as: In mathematics, the convex hull or convex envelope for a set of points X in a real vector space V is the minimal convex set containing X (...
11
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2answers
3k views

What are the implications of invalid geometries

I've imported some data in a Postgis database and some of the geometries are reported invalid (ST_IsValidReason reports self-intersection or ring self-intersection). The queries I am performing don't ...
22
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2answers
10k views

How can I find a point inside a polygon in PostGIS?

How can I find a point that is guaranteed to be within a given polygon in PostGIS? I am aware of the ST_Centroid function. However, the centroid is not always within a polygon, see below: ...
6
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2answers
2k views

Unions of polygons (Postgis ST_UNION for Geography type)

I am looking for a function that will return the intersection of 2 or more polygons (geography type). I am aware of ST_UNION, ST_COLLECT but it works only for geometry type.
5
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3answers
1k views

Open .NET implementation of the OGC Geometry Object Model from Simple Feature Access 1 specification?

I am looking for a .NET implementation of the geometry object model described in OGS's Simple Feature Access, Part 1 specification. Preferably lightweight. I don't need WKT support, just the ...