Questions tagged [point-in-polygon]

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

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1answer
9k views

Geodjango - trying to get points within a polygon

I'm going through the Geodjango tutorial and trying to implement in my own project - I have loaded data from a shapefile into my model/database and I have a separate model that has a PointField. I am ...
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1answer
856 views

Closest point on a line segment from point outside the line

From the above pic I found the value x from line (p1,p2) and point a. Using y=mx+b and an imaginary red line which is perpendicular to the black line having slope -1/m and the intersecting point x, ...
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1answer
3k views

How to create randomly points within polygons for each row of a dataframe matching a Polygon ID with R

My question is similar to this post, but because there are no "perfect" answer and above all no reproducible example I open this question. I have a "SpatialPolygonsDataFrame" and a data frame. Both ...
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2answers
2k views

How to determine in which grid cell each coordinate of an x,y series is located?

I have a circular arena which I have divided into a number of equal-sized 'cells' using a grid-like arrangement of concentric circles and line segments (in grey below) and also a series of x,y ...
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1answer
255 views

Count points in a polygon that changes form ("on the fly calculation")

I have tried to find a plugin for this, with no luck. Perhaps someone knows of a plugin that can do the following: In this project I create a lot of polygons that contain points, and the size of the ...
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1answer
1k views

Find polygons that contain a specific number of points

I want to make a polygon selection based on a specific number of points. For example, I want to select those polygons that contain more than 30 points. I don't want to select every polygon that ...
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2answers
1k views

Finding all points in linestring that are contained by polygon using PostGIS?

I have a linestring made up of 4D points and I need to determine which points in this linestring fall within a specific bounding box so that I can get the Z dimension of those points. I'm using Python ...
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1answer
123 views

Adding points in Empty Polygon using ArcGIS Desktop?

I have a number of polygons on which I wish to make analysis using points data symbols. Is there a method through which I may add points automatically within each polygon in separate locations? For ...
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1answer
2k 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 ...
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2answers
2k 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
4k 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
116 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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1answer
801 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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2answers
798 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 ...
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1answer
1k 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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4answers
30k views

Overlaying spatial polygon with grid and checking in which grid element specific coordinates are located using R [closed]

How can one use R to split a shapefile 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 ...
3
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1answer
243 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
128 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" ...
8
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1answer
26k 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. ...
0
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1answer
57 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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3answers
4k views

Finding row that has shapefile containing lat/long point in PostGIS geometry column

I am fairly new to PostGIS and I'm trying to return a row in my table that has the shapefile containing a lat/long point I pass in via st_contains. Below is a query I wrote myself that brings back 0 ...
2
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1answer
3k 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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1answer
15k 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 name="...
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3answers
260 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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4answers
3k 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 ...
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2answers
3k views

Python - GDAL : Polygon to point shapefile

I want to read all the points in a polygon shapefile and use their coordinates to make a new point shapefile, then find the min and max of the X coordinates. So here is the code I wrote for the first ...
2
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1answer
1k 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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4answers
22k views

Intersection between points and polygons in QGIS

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 the "Intersect" function was the ...
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0answers
783 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 QGIS,...
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2answers
10k 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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0answers
655 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 given ...
2
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1answer
883 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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2answers
8k views

Checking if Lng and Lat fall inside polygons from ESRI Shapefile

I have two input files. First: CSV file with a list of points each defined with Lng, Lat, Name Second: ESRI Shapefile defining a number of polygons I would like to determine for each point I have (...
54
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2answers
106k views

Selecting features within polygon from another layer using QGIS

I'm using QGIS 1.8 with a PostGIS database and I have three PostGIS layers in QGIS a lines layer, a points layer, and a polygon layer. I'm trying to select features in the polygon layer and mark all ...
4
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2answers
525 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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0answers
888 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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0answers
315 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 ...
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0answers
270 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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2answers
16k views

Counting 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 tables: ...
8
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2answers
7k 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, Lat,...
4
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1answer
2k 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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2answers
3k views

Function for Selecting Points in a Polygon

I've been banging on this for a few hours, but since I'm relatively new to PostgreSQL and PostGIS, I can't find the solution. I'm trying to create a stored procedure (function) which will return all ...
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1answer
98 views

Display county for random points

I have a county level shapefile 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 ...
3
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1answer
707 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 ...
6
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1answer
925 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 ...
12
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1answer
8k views

Updating field to give count of points in polygon using STIntersects?

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 (dbo....
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0answers
387 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 ...
9
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4answers
57k 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?
10
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2answers
2k views

Update database row with points that fall within polygons

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 point ...
5
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1answer
242 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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