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

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18
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2answers
5k views

Looking for fastest solution for Point in Polygon analysis of 200 million points

Apologies for asking a question that has been asked before -- I've read through answers, and I'm left wondering how to implement the recommendations. I've never used SQL, Python, C, and have only ...
16
votes
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: ...
13
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 ...
10
votes
1answer
392 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 ...
7
votes
2answers
190 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 ...
7
votes
2answers
2k views

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 ...
6
votes
4answers
1k 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 ...
6
votes
1answer
1k 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 ...
6
votes
3answers
223 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 ...
6
votes
2answers
3k views

Create a polygon layer from point data

I'm currently using QGIS 1.8.0 I would like to create a polygon layer from a point dataset, where the size of the polygons relates to the resolution of the grid reference. The ultimate aim would be ...
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 ...
5
votes
3answers
841 views

How to identify feature vertices that are part of a donut hole in ArcGIS 10?

I´m exporting the coordinates of polygon vertices to a CSV-File using the "Feature Vertices to Points" and then the "Export feature attributes to ASCII"-tools. Some of these polygons have holes ...
5
votes
2answers
2k views

Point-in-polygon using Python and OGR

I want to use OGR in Python to write a simple point-in-polygon test: def point_in_polygon(point, polygon): """ point : [longitude, latitude] polygon : [(lon1, lat1), (lon2, lat2), ..., ...
5
votes
1answer
135 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. ...
5
votes
2answers
491 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
859 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 ...
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 ...
4
votes
1answer
988 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 ...
4
votes
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?
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
votes
1answer
1k views

How do I add polygons to an existing attribute table where the data is stored as points? ArcGis 10

I have a shape file of golf courses saved as points, I would like to digitise the boundaries and add the polygons to the existing attribute table. I have opened editor and clicked on the point data ...
4
votes
1answer
394 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 ...
4
votes
1answer
507 views

Calculation of average point distances from one another within a polygon grid

I am working with processed LiDAR data of forested areas in ArcMap 10, with various area based statistics extracted for each 30x30m polygon grid-cell in a shapefile. There are approximately 20,000 of ...
4
votes
2answers
547 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, ...
4
votes
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 ...
3
votes
3answers
693 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 ...
3
votes
2answers
104 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 ...
3
votes
2answers
3k 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 ...
3
votes
1answer
700 views

Correct way to perform point-in-polygon queries on streaming point data?

Short version: What is the "correct" Esri-based solution to the presumably-common scenario of receiving dynamic asset location data (eg. aircraft), checking to see whether those points are within any ...
3
votes
2answers
203 views

Points in polygon by months

I have two tables: points(gid,id,datum,x,y,geom) and hexa_grid(gid,geom). I must create new table hexa_grid_pip (gid,2008_01,2008_02 ... 2011_12, geom) In column 2008_01 ... 2011_12 must be number ...
3
votes
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" ...
2
votes
2answers
1k views

Is it possible to extract Coordinates of Polygon Centroid in QGIS?

I have created polygon centroids using one of the "Geometry Tools" but I would like to extract the actual coordinates into Excel for further work. Is this possible?
2
votes
2answers
138 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 ...
2
votes
3answers
80 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 ...
2
votes
3answers
833 views

Accessing coordinates of polygon

I have designed a polygon in a web page and the coordinates are stored in the database of the type polygon. However when I check the database, I find GEOMETRY - 120B under polygon field. What does ...
2
votes
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 ...
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 ...
2
votes
1answer
589 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 ...
2
votes
2answers
417 views

Map Coordinates to Neighborhoods from MySQL Table

I have a MySQL database with a set of coordinates and a shape file (Zillow Neighborhood Database for Chicago) containing the boundaries for each neighborhood which I have converted to a spatial ...
2
votes
1answer
200 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 ...
2
votes
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 ...
2
votes
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, ...
2
votes
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 ...
2
votes
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" ...
1
vote
2answers
47 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: ...
1
vote
1answer
957 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 ...
1
vote
2answers
407 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 ...
1
vote
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 ...
1
vote
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 ...
1
vote
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 ...