Tagged Questions

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

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31 views

How to generally determine if a Point is inside a Polygon/Region?

I have a region (i.e. closed polygon) like this given in cartesian coordiantes: 1: 628497 / 239586 2: 642383 / 249881 3: 657705 / 241262 4: 652677 / 230489 5: 631370 / 231446 6: 628497 / 239586 I ...
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1answer
24 views

Point-in-polygon using WGS84 geographic coordinate system

When running a point-in-polygon operation, is it valid to run that with polygon features in straight up WGS84 and a point in lat/lng, or should both be projected into a non degree based coordinate ...
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27 views

Capturing points slightly out at sea

I have two tables one containing points (points) and the other polygons (polygons). I want to generate a two-columns table identifying for each point of the first table the polygon containing it. So ...
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3answers
49 views

How to Count point in polygon + on boundary?

So I'm looking for suggestions in both ArcGIS 10.2 and QGIS on methods on how to count points within a polygon and points that fall on a polygon boundary without adjusting the data/points. The ...
1
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1answer
15 views

Point in zone problem in calculation

I have a strange problem that i believe its because the zone pass through international date line. My goal is to find if a point is within a zone and I use the geoPHP library, everything seems to be ...
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0answers
30 views

Match housenumbers on buildings (special case of point-in-polygon-test)

Task with example I'm working with geodata (country-size) from openstreetmap. Buildings are often polygons without housenumbers and a single point with the housenumber is placed within the polygon of ...
2
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2answers
54 views

Finding a point inside a polygon based on maximum value of a specific field

I have a Polygon Shapefile that represents US counties and a Point Shapefile that represents hospitals. The hospital attributes table includes fields like "Number of Beds", "Number of Patients" and ...
2
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0answers
47 views

QGIS assign multiple points data to closest polygon

I've got two layers: point layer polygon layer I need to add the points attributes to the polygon by location (if the point is on top of polygon add the atribute as a new field. I thought of ...
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2answers
45 views

Postgis: Point-in-polygon check + feature attributes inheritance

I have two tables in Postgis 2.1 database: Polygon features with a reach attributive information; Regular point grid; I would like to get a SQL query returning the regular point grid with ...
1
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1answer
68 views

Find all street names or addresses within a polygon

I have a geojson list of lat/long coordinates that make up a custom polygon of a section of my county. Ideally I would like to be able to find all the addresses that are within the polygon boundaries. ...
2
votes
1answer
57 views

Positons from GPS lanes inside a polygon

i have a lot of lanes like the orange lanes at the below picture (latitude and longitude values). Now i need all values from each lane inside the red polygon. What is the easiest way to realize ...
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2answers
90 views

Select points within a polygon and update attributes

This seems really simple but I can't get it to work. I have two feature classes, a polygon of sales areas for a city, and point layer of addresses. I want to select the addresses based on the sales ...
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0answers
41 views

Using Geoserver

I am new to GIS and interested in using Geoserver. I have had a look at tutorials and read some books on this but still feeling clueless. I intend to use C# to accomplish some tasks eg, plot points on ...
1
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0answers
34 views

node.js GeoLib fails on polygon that straddles the anti-meridian

geolib.isPointInside does not appear to work correctly when the polygon longitudes straddle the anti-meridian. I maintain a system with lots of polygons that do straddle the antimeridian (I'm in ...
1
vote
1answer
60 views

Associating location data from PostGIS for a Choropleth map?

I'm trying to build my first choropleth map from data that we have stored in our PostGIS enabled Postgres database. So far I've been able to build a map on Mapbox using a topojson set of UK postal ...
2
votes
1answer
45 views

How to get only one biggest point in polygon?

I have polygon and point feature classes. Every polygon have 2 points inside them. For output I need only one point with highest value. I need incorporate this step in ModelBuilder. I had idea about ...
1
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1answer
246 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 ...
1
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1answer
77 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 ...
3
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1answer
83 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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0answers
75 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.
2
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2answers
114 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 ...
0
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1answer
35 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
68 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
125 views

Find all points in a linestring that are contained by a polygon

I'm fairly new to PostGIS, so I apologize if this has been answered before. I have a linestring made up of 4D points and I need to determine which points in this linestring fall within a specific ...
1
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1answer
96 views

Adding points in Empty Polygon

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 ...
2
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0answers
69 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
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2answers
60 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: ...
0
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2answers
276 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 ...
1
vote
1answer
44 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 ...
1
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0answers
65 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
3answers
146 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 ...
1
vote
1answer
129 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 ...
7
votes
4answers
1k 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 ...
2
votes
1answer
58 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
votes
1answer
58 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" ...
4
votes
1answer
963 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
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
2answers
302 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 ...
1
vote
1answer
62 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 ...
0
votes
1answer
1k 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 ...
0
votes
0answers
128 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 ...
2
votes
3answers
98 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 ...
1
vote
3answers
484 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 ...
1
vote
2answers
744 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
185 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 ...
0
votes
2answers
259 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 ...
1
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0answers
130 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
votes
0answers
55 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 ...
0
votes
1answer
1k 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 ...
1
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0answers
142 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 ...