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

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6
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4answers
2k views

Point in polygon algorithm for multiple polygons

I've a Google map with bunch of polygons on it. Here is a problem I'm interested in: Given a lat,lng point, what's the best way to determine all the polygons that this point lies in? The obvious way ...
3
votes
1answer
3k views

How to determine if a mouse click falls within a polygon

I have a polygon drawn on top of a layer using the graphicsContainer of the current activeView, then I want to be able to show a custom context menu if the user right clicks INSIDE the polygon. So I ...
17
votes
7answers
2k views

Fastest way to spatially join a point CSV with a polygon Shapefile

I have a 1 billion point CSV file and a shapefile with around 5,000 polygons. What would be the fastest way to spatially join points and polygons? For each point, I need to get the containing polygon ...
6
votes
1answer
2k views

Performance Gain Through GIST Index for Point in Polygon Query

I have two tables: locations(id,region_id,the_geom) and regions(id,the_geom). For each location point I want to determine the region it is located in: UPDATE locations SET region_id = (SELECT id ...
3
votes
3answers
755 views

In ArcGIS how can I append the number of points that are located inside each individual block groups of the entire US?

I am using ArcGIS 10 and I have 2 shapefiles; (a) a polygon shapefile of block groups of the entire US, (b) a point shape file of customer locations throughout the US. What I want to know if how many ...
5
votes
2answers
613 views

Does anyone know a function to determine if a Point lies on a polyline?

ArcEngine 10 .Net 4 c# Hi I'm currently allowing user to select a point on a polyline and creating a point on the line. I am using snapping tool. I just want to make sure that when the user clicks ...
5
votes
2answers
1k views

Creating polygons from a one to many relationship of points

I have a set of polygons that are in a one to many relationship with points. The polygons are administrative boundaries and the points have information on companies and percentage of ownership . I ...
8
votes
2answers
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Creating evenly distributed points within an irregular boundary

I need to create an evenly distributed series of points within a series of oddly shapped polygons (formerly squares, but now squares with donut holes). The way I have solved this problem so far is to ...
3
votes
2answers
4k views

Select points under polygons?

Dear all, I apologise if this is answered elsewhere, but I cant find it. I have a point layer and a polygon layer (created from the point layer using local convex hull isopleths). I would like to be ...
10
votes
1answer
435 views

Spatial operators in R?

How can I do spatial selections or filters in R? I can do this in PostGIS using (e.g.): SELECT * FROM mypoint, mypoly WHERE ST_Within(mypoint.geom, mypoly.geom); and it is similarly a piece of cake ...
4
votes
1answer
455 views

Convert Landmask file into WKT Polygon

I have a land mask file in netCDF (also in ascii, if needed) which basically consists of a lat/long pair and a boolean (1 or 0) determining if that value is over land or not. The thing is, I'm not ...
17
votes
2answers
5k 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: ...