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

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42 views

How to find all features in one table that intersect features in another table in PostGIS?

I have two tables, boundary polygon table and location point table. I need to find all boundary polygons that contain at least 1 location point. What is the proper way to do this in PostGIS? I tried: ...
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2answers
49 views

Find maximum and minimum value of points within a polygon buffer?

I have a series of 500m buffer zones along a polyline. I also have a series of points following the line, each point represents a 10m x 10m cell. I calculated the values of a field in each point known ...
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1answer
28 views

Weird ST_Contains behaviour

I'm creating a polygon and then checks whether one of the origin points is contained inside the polygon. To my surprise, I get False (?!) What is wrong here? SELECT ST_contains(ST_GeomFromText('POINT ...
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0answers
16 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 ...
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0answers
45 views

How to count points once with overlappying polygons?

All, We're using parcel data (polygon) to count student locations (point) based on parcel type. We're doing this using SQL and the ST_Intersects function. It works great, except the City and County ...
6
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3answers
219 views

Overlay a spatial polygon with a grid and check in which grid element specific coordinates are located

How can one use R to split a shape file in 200 meter squares/sub-polygons, plot this grid (incl. ID numbers for each square) over the original map below, and evaluate in which square specific ...
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1answer
43 views

PostGIS ST_Within returns zero data

I am using PostgreSQL 9.3.3 & PostGIS 2.1.1 and I have a table Entries which has a column called "latlng" of geographic type (this column stores entry's latitude and longitude coordinates). I am ...
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1answer
45 views

Identify geographic location to points

I am quite new in QGIS and I really need your help. I have a map of Kenya divided into 68 districts and I have coordinates of 30.000 schools. The points have one variable besides the latitude and ...
3
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1answer
41 views

Qgis creating point within complex shapes (with holes) [duplicate]

I'm looking for a tool to create a point in every polygon, that will be placed in the polygon. these are complex shapes with holes. the point must not put in those holes! the "plugin RealCentroid" ...
5
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1answer
129 views

Shapely unable to tell if polygon contains point

For an application I want to determine under which constituency a given coordinate falls. After looking at the various options, I decided upon shapely and fiona as the easiest way to implement this. ...
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1answer
26 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
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2answers
135 views

How to find the row that has a shape file containing a lat long point in my PostGIS geometry column

I am fairly new to PostGis and I'm trying to return a row in my table that has the shape file containing a lat long point I pass in via st_contains. Below is a query I wrote myself that brings back 0 ...
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1answer
41 views

Use field calculator in QGIS so get number of points in polygone and store it in attribute table

I have to layers, one point one polygon (with 6 areas) stored as shapefiles. Now I want to count the number of points in each area and write it into the attribute table of the polygons. A column ...
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0answers
67 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 ...
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1answer
298 views

How to find points inside each polygon in Mysql?

I have points table (with latitude and longitude columns) and polygons table with geometry stored in Mysql. I want to get points inside one polygon, for example in polygon which has column ...
3
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2answers
103 views

How to query for a specific point, within a specific polygon?

I have a shapefile points layer, with each point representing either Marginal, suboptimal, or optimal conditions. I want to find only the marginal points within a specific polygon from my catchments ...
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1answer
578 views

How to extract polygon location data (County) to a point shapefile (only has DMS)

I have imported an excel spreadsheet to my map and the points have fallen into certain locations. How do I add the location of the polygon that the point has landed in, to the attributes table of the ...
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3answers
79 views

How to write FIDs of points within each polygon to polygon field?

I have two feature classes one with points one with polygons (in ArcGis 10.2). Now, I want to write into a String Field of the polygon layer a list of all the Point-FIDs that are within each polygon ...
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2answers
219 views

How to create random point in according polygon for each dataset entry in a list (with R)

I have an area divided into polygons, and a dataset of observations which has a common field with the polygon layer. I now would like to generate a random point for each dataset entry within the ...
2
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1answer
199 views

Tearing in ggmap (R) after using spTransform and random point generation using splancs

I am using R and the package ggmap to try and generate some random points within the city limits of Chapel Hill, NC. I have downloaded the shapefile for the town of Chapel Hill from the Orange County ...
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2answers
403 views

Python - GDAL : Polygon to point shape file

I want to read all the points in a polygon shape-file and use their coordinates to make a new point shape file. then find the min and max of the X coordinates. So here is the code I wrote for the ...
2
votes
1answer
132 views

Fast zipcode detection from latitude/longitude

I need a way to get the zipcode of a lat/long pair fast (<10 ms), and at a high rate (thousands of qps) I've loaded a shapefile from the US Census Bureau into a mysql database with spatial ...
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2answers
108 views

Intersection between points and polygons in QGis

I have the following problem. I have a shapefile of points and a shapefile of polygons. I want to know WHAT points (not how many) fall inside EACH of the polygons of my multipolygon shp. I thought ...
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0answers
73 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 ...
2
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1answer
588 views

How to find most frequent values?

Entry layers: polygons - no attributes (columns/values), points - needed attributes (columns/values) How to get this result?: polygon layer with attribute (column/value) of most often (most frequent ...
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0answers
54 views

What is the MS SQL Spatial syntax for counting points within polygons? [duplicate]

All, What I'm trying to do is this: Count points within polygons There are thousands of points and maybe 2 dozen polygons Get a list back of the 2 dozen polygons by name and the count of points ...
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0answers
105 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 ...
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2answers
3k 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: ...
1
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1answer
80 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 ...
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1answer
77 views

Add buffer only on one specific side of polygons

I have a shapefile with multipart geometry (multipolygons), namely communities (blue on the picture below). There are also lakes (white), but for these I don't have a geometry, they're just "empty". ...
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0answers
99 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. ...
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2answers
283 views

Checking if Lng and Lat fall inside polygons from ESRI Shape file

I have two input files. First: CSV file with a list of points each defined with Lng, Lat, Name Second: ESRI Shape file defining a number of polygons I would like to determine for each point I have ...
2
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1answer
2k 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 ...
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0answers
22 views

Calculating Centroid of add shaped polygons [duplicate]

I need to calculate the centroid so that it is still contained in the related polygon. I have used the centroid tool in ftools and the centroid maker and have the same results as shown below. Is ...
2
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0answers
98 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, ...
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3answers
2k views

How to check if a point is near or inside polygon?

I am trying to find a simple library which can do point in polygon. Earlier i did hit Java Spatial Index library ...could not figure out. Tried openmap..looked simple didn't work. I am totally new ...
2
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0answers
133 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 ...
4
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1answer
355 views

MongoDB: Search for polygons which have a certain location

Good day :). I am trying to implement a search feature on MongoDB using Mongoose.js , the short version of which is this: I tag locations on a map as polygons. and give them names. Then when an user ...
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0answers
102 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" ...
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1answer
949 views

Count Points in Polygon with Postgis

I've got a simple problem: I want to count the number of points within a set of polygons. I have a SQL already but it only gives back the gid of the polygone that actually contains points. My ...
4
votes
2answers
542 views

Total of attribute field of point layer per polygon layer

I have a polygon shapefile of many lakes, I also have a point shapefile of locations on those lakes where fish were caught. The point shapefile contains the attributes: Fisherman_iD, Fish_Caught, ...
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1answer
51 views

Display county for random points

I have a county level shape file for South Carolina. I generated random points using Vector->Research Tools-> Random Points. The Attribute tables for the random points layer has only the ID included. ...
4
votes
1answer
983 views

STIntersects - Update field to give me count of points in polygon

I have a points layer (dbo.ptLayer) Around 1M points Spatial Geometry Type (dbo.ptLayer.geom) No spatial index just yet, but will create one once data gathering complete. I have a polygon layer ...
5
votes
1answer
378 views

How to determine optimal windmill placement to maximize production?

How can I add automatically the maximum number of points (dots) with 6m diameter and 100m distance each point from other into an area. The dots will present the windmill base (6m) and I want the ...
4
votes
3answers
5k views

Solving the Point in Polygon Problem Using Google Maps and Fusion Tables

The Point-In-Polygon problem is fairly well documented on this forum. My question is if there is a way to use Google's free tools, i.e. Google Maps, Fusion Tables, and possibly Google Refine, to solve ...
4
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3answers
2k views

Check if lat/long point is within a set of polygons using google maps

I know how to do the above using Esri (Query task on shapefile), but can this also be done using Google Maps? Do I have to query each polygon or is there one method to query a set of polygons?
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226 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 ...
7
votes
2answers
189 views

Update database row with points that fall within polygons

All, I have a PostGIS/Postgresql DB that has two tables in it. One with point geometries and the other that represents country boundaries as polygons. I would like to add the country name that each ...
5
votes
1answer
166 views

Which polygons surround this point? A practical case of political geography

I'm starting a project from scratch but am budget constrained. In plain language I've got no money. What I want is to provide an address and return what governments have jurisdiction there. The ...
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1answer
143 views

How to add a label of a point to a polygon

i have several polygons with in each polygon a point with a label (number). I want to add the label in the polygon to the attribute-table of the polygon it belongs to.