A common GIS operation. Used to determine whether a point lies within a polygon's bounds.

learn more… | top users | synonyms

1
vote
1answer
86 views

Finding point in polygon

I want to calculate a point in a polygon, if the centriod falls inside the polygon it is what I want, but if it doesn't I would like it to be a visual center point. Essentially I want to do the ...
0
votes
1answer
28 views

Determine when a route enters and leaves a polygon

I have all of the segments of a route from White Horse, YK to Miami, FL. Now I want to determine how many miles I travel in each State / Province. I have Polygons for each State and have been able ...
2
votes
0answers
110 views

ray casting on earth's surface

Is it safe to use ray casting algorithm to check if a coordinate is inside a polygon specified as coordinates? Purpose of my question is because the longitudes are not parallel in a Cartesian sense, ...
2
votes
0answers
159 views

How can I improve my Ray casting algorithm?

I have been using the following function below which have been working well to decide if a point in the polygon but once I have many points which is building the polygon say over few thousand it seems ...
2
votes
0answers
113 views

Matching points in table to polygons

this is my first post to this forum. I hope to start participating actively. I have a table with several records (aprox 200.000), each with its own coordinates. And I need to identify the "Polygon" ...
1
vote
0answers
44 views

Programmatically selecting features by polygon

Expanding upon this post how could you use QGis to programmatically draw a selection polygon and select features within the polygon? I have been using QgsMapToolEmitPoint(self.canvas), to find and ...
1
vote
0answers
38 views

Using polygons with libspatialindex

I am investigating using some C/C++ libraries for point-in-polygon lookups and libspatialindex seems popular. I've written some code that seems to do what I want but I'm not entirely sure if what I ...
1
vote
0answers
91 views

DotSpatial: Convert a Polygon Feature to System.Drwing.Region

I want to paint a Polygon region with a color. I know I can use Symbolizer to do this but I want that region to blink (change it's color in a timer) and using symbolizer seems to be slow for this ...
1
vote
0answers
101 views

Divide polygon based on points for even distribution

If I have a point layer, how can I create a polygon that includes all of the points and divide that polygon into n sections in which each section contains an equal number of points? Preferably in ...
1
vote
0answers
126 views

Can I get a list of points in a polygon using Quadtrees?

I'm storing vertices in a PR (or PM if needed) quadtree and would like to be able to: Find out if a given polygon contains at least one point Optionally: Get a list of all the points within a ...
1
vote
0answers
232 views

How to update polygon field with point count for multiple rows? (Temporal point-in-polygon)

I have a shapefile with several regions. It contains basic info like ID, Code, Name1, Name2, etc. It is overlaid with a shapefile of points (nearly 200k). Each point represents an event with a type ...
0
votes
0answers
44 views

Creating a polygon around features

I want to create a polygon around a number of points so that all the points occur within the polygon. The purpose is to do this to a number of different features and see where they overlap.
0
votes
0answers
133 views

Point in polygon analysis fails with “TypeError: arguments did not match any overloaded call”

I am using QGIS 1.8 on Windows 7 I want to perform a point in polygon analysis using the Vector > Analysis Tools menu. My point layer is the result of a SpatiaLite query which returns 10'000 points. ...
-1
votes
0answers
39 views

how to determine the direction in point-in-polygon

I am very new to GIS and I am wondering if the following problem could be solved or not. Given that there are three pairs of points(A<-B, C->D, E<-F) Each pair of points has a direction and ...