On a map, a closed shape defined by a connected sequence of x,y coordinate pairs, where the first and last coordinate pair are the same and all other pairs are unique.
2
votes
3answers
382 views
Split polygon with holes to get several hole-less polygons
Unlike this thread I actually need to split the polygons into several hole-less polygons. I'm not sure on how to approach to this problem.
I have polygons with holes of many diferent shapes, like ...
2
votes
1answer
245 views
How to display only one pie chart for polygon features in QGIS?
I'm working with Qgis on a project and I have a small problem.
I have to do some demographic research and therefore I have a .shp file from a given country with 10 districts for example.
Now, I know ...
2
votes
3answers
545 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
466 views
How do I subdivide and edit polygons preserving topology?
I'm using QGIS. I have a layer made up of many adjacent polygons - let's call them "countries". I currently use the Atlas plugin to export each "country" polygon to a .png file.
I want to further ...
2
votes
1answer
268 views
SUM Area irregular polygons per grid cell
I have a shapefile of irregular polygons and a GRID (both as raster and polygon grid). How can I count the AREA SUM of irregular polygons per grid cell?
Can use ArcGIS, QGIS or R.
(Application: ...
2
votes
1answer
53 views
Evaluate minimum points required to define polygons based on an error threshold
I need to build a model or write an algorithm to do this, which I would like you to share your ideas with me.
here is my cadastral problem: I have plenty of polygons and I need to make a report of ...
2
votes
1answer
58 views
Remove intersect of one polygon from another in R
I am trying to remove the intersect from Poly2 onto Poly1. Below are the coords of the 2 polygons.
> coords1
[,1] [,2]
[1,] 992.0161 7462.531
[2,] 950.1962 7413.532
[3,] 902.3632 ...
2
votes
1answer
280 views
How do i calculate line segment lengths within a polygon?
I have a layer with line segments and a layer of polygons (in this case, buffers around points). I need to create a new field for each polygon that contains the total length of all line segments ...
2
votes
1answer
76 views
What is the PostGIS function for retrieving buildings by road side?
I want to get information of buildings by the road side only. Assuming that the building table has multi-polygon geometry and the road table has multi-linestring geometry, what would be a pgSQL Query ...
2
votes
2answers
311 views
Problem creating polygon features using ArcObjects / ArcGIS 10
I need to create a grid of polygons. Each polygon is rectangle, thus has 4 corners (vertices). When I create polygon features using ArcObjects they seem to have wrong geometry, which results in wrong ...
2
votes
1answer
79 views
Compiling a list of units that border each other
I have a shapefile of U.S. counties. I am interested in compiling a list of those that border each other.
In particular, I am interested in those that border each other but are in different states. ...
2
votes
1answer
208 views
How to meassure the length of common edges between polygons?
I have a shapefile that contains several polygons which in fact represent the limits of several counties. My task is to find each length of each shared border. So in other words I want to know how ...
2
votes
1answer
199 views
determine whether a circle intersects a county boundary in postGIS
I'm using PostGIS 2.0.1 and need to determine whether a circle (center + radius) intersects a county boundary (polygon).
The query I'm using is this:
SELECT DISTINCT(u.id) FROM siteareas_poly sa, ...
2
votes
1answer
121 views
Merge section polygons in PLSS
I am trying to merge quarter quarter sections of polygons from PLSS into a quarter section.
However, I also want it assigned to correct Township/Range/Section while merging.
I know I can hand merge ...
2
votes
1answer
663 views
How to make a predetermined Polygon (Circle) From 4 Coordinates, The Radius and Center Longitude and Latitude in Openlayers
I know how to make a predetermined Polygon in Openlayers (see below).
Please have a look at http://studio.netnrg.co.za/dev/rnd/blake.loizides/openlayers
var feature2 = new ...
2
votes
1answer
397 views
Openlayers Polygon not visible
I have just recently started playing with mapping but have had limited success. I have been able to create/display markers, but in my current project I am trying to display zipcode areas by creating ...
2
votes
1answer
477 views
Conversion of raster features to polylines: skeletonization?
I would like to identify linear features, such as roads and rivers, on raster maps and convert them to a linear vector features (i.e. polylines). I typically use R as my primary GIS, and have posed ...
2
votes
1answer
161 views
Best Method for Validating polygons?
I would like to assess the spatial accuracy of a load of polygon shapefiles which are supposed to show air quality for a bunch of countries. Firstly I want to assess whether each shapefile has a ...
2
votes
3answers
127 views
Best program for crowd-sourced polygons on Gmaps
Looking for a way to crowd-source polygon creation on GMaps (in a wiki environment) that doesn't involved ESRI's expensive server software.
Requirements:
- a bunch of different wiki pages can be ...
2
votes
2answers
2k views
How to automate point-in-polygon queries in ArcView?
Layer1 = point shapefile (multiple points, geocoded)
Layer2 = polygon (1 attribute; (1,2,3...))
I want a non-gis person to be able input a single address and be told the attribute of the polygon ...
2
votes
1answer
48 views
How to determine the longest side of a polygon in QGIS?
Is there a possibility to determine the longest side of a polygon with QGIS? As I need to do that for hundreds of polygons I would prefer an automized method (like a plugin).
So far my idea was:
...
2
votes
1answer
63 views
How to delete one polygon from a multi polygon record in a spatialite database using QGIS
I have a spatialite database with multi polygon records within the database. When i try to edit these records i cannot delete just one of the polgons for a specific record. It only allows me to delete ...
2
votes
1answer
114 views
R: How can I create a polygon from several polygons and a line?
I have some spatial objects that I want to combine, namely three polygons and a line. The ultimate goal is to create a polygon that I can overlay on an area of a map of administrative divisions of the ...
2
votes
1answer
95 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
1answer
122 views
find polygon corner coordinates
I am trying to get the coordinates of each node of the polygon I create. I would like the attribute table to display the name of the polygon (ex. address) and then the coordinates of the nodes (ex. ...
2
votes
1answer
77 views
In OpenLayers, is there any way to convert polygons to tiles?
I have a OpenLayer map which by enabling a feature by user, a very huge table of polygons (lots of small areas, with information and metadata for each) will appear on the map, which rendering this big ...
2
votes
1answer
113 views
How to remove a hole from a polygon in OpenLayers?
Is it possible to remove a hole from a polygon by using OpenLayers?
How can I do so?
2
votes
1answer
101 views
Obtain normalized raster average per polygon?
I have a raster that contains percentages of total forest killed plus a polygon layer that defines different zones.
My goal is to find a good statistical representative that describes the forest ...
2
votes
1answer
112 views
joining a table from zonal statistics as table with a layer, problem with reserved names
I have a raster file (percentage of total forest killed) and a shapefile with polygons (municipalities). I thought as a first step I would like to find out which municipality shows the greatest ...
2
votes
1answer
202 views
Software for building non-overlapping sets of polygons?
We have multiple populations of patients spread out over geographic distances. For each population, we want users to easily define non-overlapping polygons. The outer borders are likely to be U.S ...
2
votes
1answer
472 views
Convert shapefile in NAD27 from meters to decimal degrees to match xy data?
I have a shapefile of a boundary (polygon) that has the following projection:
NAD_1927_UTM_Zone_11N
Projection: Transverse_Mercator
False_Easting: 500000.00000000
False_Northing: ...
2
votes
1answer
460 views
Geometryutil, simplify polygon, querytask and query fault error
One of the tools in my app is to draw freehand polygons (counties) to show points (companies) in each county. Everything works great but if the user creates an intersecting polygon then I have a ...
2
votes
1answer
536 views
how to get Coodinates after Resizing a feature Openlayers
I'm trying to display the coordinates of a Feature or vector layer after I use the modify radio button to resize my vector, but it does not work, nor on my drag feature. I'm using ...
2
votes
2answers
786 views
How to subtract Geometry Point Polygons in OpenLayers?
I have two json arrays, one for background polygon and one for other polygon.
And from them, I got two polygon layers.
backgroundLayer = new OpenLayers.Layer.Vector("Background Layer", {styleMap: ...
2
votes
1answer
500 views
Calculating the outer boundary of several Geometry objects in SQL Server 2008
I have lots of Polygons of datatype Geometry in SQL Server 2008. The image below shows how a select of all these Geometrys looks visualized.
What I need to do is create a Polygon which represents ...
2
votes
2answers
487 views
How to query data from a vector map (shapefile)?
We want to obtain the specific place of the boundaries of a shapefile. We want to be able to get the points of each polygon corresponding to a specific place in order to use these data in an ...
2
votes
0answers
26 views
Clipped raster leaks outside polygons
I am trying to clip a raster (DEM) with a polygon layer in ArcGIS10.1, using Data Management>>Raster>>Clip. Basically the clipped raster has many pixels outside the polygon boundary, mainly for thin ...
2
votes
3answers
48 views
How to divide a polygon with another polygon
I am working in ARCMAP 10.
I am trying to divide a polygon with another polygon. I don´t want to clip any part away, but only divide the polygon?
The polygons are stored in two different layers.
2
votes
0answers
72 views
Problems converting polygon to point
I'm trying to convert polygons to points with ArcGIS 10. My polygon layer has 2 attributes that I want to give to my point layer. I'm using the Feature to Point function from the Arctoolbox, but it ...
2
votes
2answers
61 views
How to make mapable geo data from a solid jpg/png
I have a bunch of hardiness zones, as you can see here: http://mangoly.herokuapp.com/workroom/googlemaps/zones/
They are solid colored PNG images. I know the geo coordinates of the bottom left hand ...
2
votes
0answers
42 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" ...
2
votes
1answer
141 views
Create a square grid polygon shapefile with python
i have the following coordinates
minx,maxx,miny,maxy = 448262.080078, 450360.750122, 6262492.020081, 6262938.950073
i wish to create a square grid of size 1 m using python.
import math
...
2
votes
1answer
135 views
Convex Quadrilateral Polygons subdivision in equal parts using Python / OGR
Consider an irregular polygon (P) which has four vertices.
I would like to subdivide P into smaller polygons as shown here http://i.stack.imgur.com/4SKhB.jpg
In the old days I was using ArcGIS 9.3 ...
2
votes
0answers
65 views
Cannot reselect polygon after modify
I've got various vector layers on a OL map.
On one layer I have a few draw controls. If I draw a polygon I can select it (the whole pop-up thing works). This also works for all the other features.
...
2
votes
0answers
93 views
How to dissolve polygons that have been split back into their original polygons?
I had a feature class containging about a thousand polygons.After some processing such as intersecting, dissolving, merging, more intersecting, I ended up with a feature class of about 6000 polys. ...
2
votes
1answer
104 views
How to join attributes of donut polygon to hole polygon in ArcGIS?
First of all I'm completely new to the realm of GIS and ArcGIS.
Basically I need a reliable way to determine a donut hole's containing donut for a few hundred thousand polygons (where the donut holes ...
2
votes
2answers
345 views
Algorithm for splitting polygons/polylines into multiple sections at 180° E/W
I have code (in C++) that draws various polygons on a map that uses a cylindrical projection (typically Mercator, sometimes Miller Equidistant if you want to be precise). For simple polygons, curves ...
2
votes
0answers
120 views
how to automate changing polygon's shape while keeping its area the same and limiting deviation from orginal centroid?
I have a polygon that was digitized based upon visually interpreting underlying values of rasters/vectors that represent a natural environment (soil type, surface roughness, slope, elevation, ...
2
votes
0answers
337 views
cant find point/polygon intersect using qgis (windows only)
below i describe the method i am using.
i have 2 machines: 1 ubuntu linux, qgis 1.4 - intersection works
2 WIN xp, qgis 1.8 - intersection dows not work
hopefully, someone will ...
2
votes
0answers
433 views
How to calculate the area of a polygon considering the relief?
I work in a fire department and i'm mapping all the fires that occur in my area, creating polygons that represent burnt areas.
my problem is that the values are not accurate... for instance, arcgis ...
