A common GIS operation. Used to determine whether a point lies within a polygon's bounds.
0
votes
0answers
15 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 ...
3
votes
2answers
35 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 ...
2
votes
0answers
39 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
71 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
43 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
1answer
134 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 ...
3
votes
2answers
93 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
109 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 ...
0
votes
1answer
36 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. ...
2
votes
1answer
96 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 ...
5
votes
1answer
180 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 ...
2
votes
1answer
193 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 ...
1
vote
0answers
119 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 ...
4
votes
3answers
629 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?
5
votes
2answers
96 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
124 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 ...
0
votes
1answer
111 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.
6
votes
2answers
1k 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 ...
2
votes
2answers
541 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?
4
votes
1answer
450 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 ...
3
votes
2answers
179 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 ...
0
votes
2answers
224 views
How to implement a spatial query on polygon data for a specific point?
I have vector data fed into a database which returns a report at province level upon querying. This is implemented in a web tool.
I want to add an extra functionality at point level, where I can ...
4
votes
3answers
479 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 ...
1
vote
1answer
360 views
Modus, Mode (Mod(X)) values assign to polygon from points values within polygons (in Mapinfo or Qgis, ArcGIS)
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 ...
1
vote
3answers
1k 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 ...
4
votes
3answers
3k 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 ...
2
votes
2answers
327 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 ...
4
votes
1answer
331 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 ...
2
votes
3answers
546 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 ...
13
votes
2answers
3k 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 ...
5
votes
2answers
1k 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), ..., ...
0
votes
1answer
287 views
CenterPoint of Polygon in ArcEngine .Net 10
I am currently trying to get the center point of a polygon. In GIS, i can see the "x" mark in the center of the polygon, but I do not know how to get it from the IPolygon object.
I tried getting the ...
3
votes
1answer
539 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 ...
6
votes
4answers
991 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 ...
1
vote
1answer
1k 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 ...
13
votes
7answers
1k 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
737 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
567 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 ...
4
votes
2answers
392 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
693 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
2answers
1k 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 ...
3
votes
2answers
2k 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
357 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
331 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 ...
14
votes
2answers
2k 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:
...
