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.

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0
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1answer
4k views

Calculate maximum and minimum elevation for a polygon layer from a DEM [duplicate]

I have a polygon layer and would like to know the min and max elevation within each polygon. My elevation layer is a digital elevation model. I'm not quite sure how to extract that information. I am ...
0
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0answers
185 views

Where can I get polygons for the Municipalities of Puerto Rico?

I'd like to find GeoJSON files to draw the polygons of municipalities of Puerto Rico. It might be nice get the Nokia Map (or any reasonable publicly available map) of the same regions and overlay ...
3
votes
1answer
395 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 ...
4
votes
3answers
4k views

Openlayers remove previously drawn polygon on starting to draw next one

Objective: At any point of time there SHOULD only be zero/one polygon(s) on a vector layer with a polygon control. I need the previous polygon to be removed as soon as user starts drawing the first ...
12
votes
5answers
6k views

How best to fix a non-noded intersection problem in PostGIS?

I'm using a PL/R function and PostGIS to generate voronoi polygons around a set of points. The function that I am using is defined here. When I use this function on a particular dataset I get the ...
9
votes
1answer
659 views

Compare spatial cluster/agglomeration patterns for polygon data

I have agricultural data in form of polygons which I would like to test for spatial clusterings/spatial agglomerations. All in all I have about 40 variables which I can aggregate and standardize in ...
3
votes
1answer
2k 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. ...
6
votes
1answer
409 views

Efficiently identifying overlapping polygons with Python

I'm parsing the NOAA severe weather alert feed and using it as a datasource for a weather alerting system. In the feed, I occasionally find a polygon entry for an alert. Unfortunately, counties that ...
1
vote
2answers
846 views

Dissolve polygons - group to others with touching corners

I am working with some data that shows land management. There are many places where corners "touch". I would like to dissolve my dataset so that features are grouped (dissolved) with those that they ...
2
votes
1answer
165 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 ...
5
votes
2answers
2k views

Tips for minimizing shapefile size without compromising geographical detail?

I work for a state government's fisheries service, and lately we've been digitizing a lot of our regulatory boundaries within the state's waters that we'd like to service out on web maps. ...
1
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0answers
56 views

Add regular points to each polygon in QGIS [duplicate]

Possible Duplicate: assign and move centroids to their polygons I'm trying to find out a method to define a unique ID based on specific coordinates for each polygon of a shp. The problem is ...
4
votes
3answers
1k views

Python OGR: convert a point geometry into polygon

I'm writing a routine for creating the convex hull envelop around shapefiles of islands. I could read the data, extract polygons vertices into a geometry and then compute the convex hull. Now I need ...
1
vote
2answers
759 views

Adding values to Fishnet Grid?

I have developed a fishnet grid for my study area. I have various datasets for the area and want to allocate a value (from one of the pre-determined datasets) to each polygon within the Fishnet. ...
6
votes
2answers
331 views

Breaking apart a polygon layer by unique values, creating many new layers

I have a large dataset of habitat information that I need to calculate distances from animal locations to the closest polygon of each habitat type. The way to do this, that I understand, would be to ...
5
votes
1answer
1k views

Create a new vector layer that fills space between other polygons in QGIS

I inherited a clipped (500m radius) land cover map containing vector layers of different land cover categories such as buildings, grass, roads, etc from a colleague. The empty (white) space in ...
3
votes
0answers
109 views

Create perimeter from given area [closed]

I need to develop a web-based application to manage areas inside a bigger area. I already have the initial perimeter, and it has irregular borders like that: . I will need to tell the app to ...
1
vote
3answers
667 views

How to create one KML per polygon (from one Shapefile)?

I have a shapefile containing hundreds of polygons. I need to create a kml of each of the polygon. Is there any way that I may not have to deal each polygon individually and my polygon file may give ...
6
votes
1answer
2k views

What is the best way to connect spatial data with attributes in Excel table?

I have many attributes which are stored in an Excel table. They refer to USA counties. I need to somehow connect those attributes to polygons in some format (don't know which is the best) and ...
7
votes
2answers
4k views

How to create a heat map or density map from stacked polygons in ArcMap 10

I have a polygon shape file that has many overlapping features. Each feature represents an area used by polar bears. So some of the polygons overlap and some don't, and there are separate clusters of ...
6
votes
2answers
170 views

Summing up over area based on distance related function?

Through a field study, we learned that the density of a bird species in the forest was related to the distance to forest edge: ln(density) = 1.89*(distance to edge) + 0.34 Now, for any forest ...
3
votes
3answers
524 views

Sorting polygons by latitude?

We have a set of polygons which we would like to sort and number according to their latitude. This will make it easier for local authorities to relate to the numbers of the objects. I have looked ...
1
vote
0answers
672 views

How to clip the contour map with the polygon using R software?

Hi I am wondering how can I create the contour lines from the discrete x, y and z dataset and then add the shapefile to cut the contour lines by polygon. I want to clip the contour map by the shape ...
5
votes
3answers
628 views

Polygonize vegetation area from Landsat7 RGB using QGis / Bilko?

I'm trying to extract the areas with vegetation as a polygon-shape from a landsat7-image, 30m resolution, RGB, using QGis 1.8 or Bilko or (hopefully in the near future) ArcGIS. The area is in Northern ...
2
votes
1answer
102 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 ...
0
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3answers
454 views

Calculate 'Rectangle' Coordinates Given 2 Points and width [closed]

I want to create a rectangular polygon using two points as guides. So let's say a journey starts in Egypt and ends in London, my polygon should have 4 points: 10 miles further from London than Egypt ...
4
votes
3answers
496 views

How to subset X number of features from Shape file in QGIS

I'm looking for a means to take a rather large Shape file and split it out into separate, smaller shapefiles based on number of features. So for example, if I have a file with 1 million features, ...
5
votes
0answers
473 views

Grouping analysis of points to divide a polygon into n number of sub-regions

I'm attempting to create n sub-regions from a polygon based on a cluster analysis of a bunch of overlapping raster layers (physical layers, eg: depth, currents, waves). Briefly, I can create a ...
5
votes
2answers
806 views

How to achieve an “inner glow” effect on polygons drawn using the Google Maps v3 javascript API?

Is it possible to produce an "inner glow" effect on polygons drawn using the Google Map v3 javascript API? If not possible using the vanilla Google Maps API, is there a 3rd party tool that can do it? ...
2
votes
1answer
550 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?
3
votes
1answer
306 views

digitizing (tolerence) error in line data

I have designed a large number of boundaries. For accuracy, I took lines in patches from different data sets and merged them into one. Now I want to turn them into polygons from lines. I every second ...
3
votes
0answers
221 views

Closest set of points to another set of (predefined) points

I have 10 sets of points which I call templates that I have manually classified from 0 to 10. Each point is a X, Y coordinate in a text file. Each template has 5-8 points. I have new sets of points ...
6
votes
1answer
622 views

QGIS define hexagon area around mapped points

I am using QGIS to map a number of radio antennas (for mobile network). Once I have the layer of the sites (done), I would like to assign to each site a coverage area (envelope). I could achieve that ...
7
votes
1answer
521 views

How to rectify polygon shapes in QGIS?

I have some polygon-shapes in qgis-1.7.0 and want to ensure that every polygon is a rectangle. See image below. Is there any way I can do this in QGIS (or any other f/oss)? Or how can I improve my ...
11
votes
3answers
388 views

How to improve drawn shapes in Quantum-GIS?

I have a polygon-shape in qgis-1.7.0 and want to fix overlays and gaps between the edges of adjacent polygons. See image below. Is there any automated way to do this in quantum-gis? Or any other ...
8
votes
1answer
9k views

How to enable “snapping” in Quantum-GIS while drawing polygons?

I tried to draw polygons in qgis-1.7.0 and I somehow can't find or failed to find the "snapping" option. I'm used to ArcGIS-10.0 where you have some snapping options, like placing points of polygons ...
9
votes
3answers
1k views

How to sum up values of neighbouring polygons?

I hope that you can help me with the following problem: I have a vector (polygon) layer. I would like to add an attribute to the layer that - for every polygon - sums the values of a specific field of ...
2
votes
0answers
117 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. ...
0
votes
1answer
738 views

OpenLayers polygon fill not working with GeoJSON file as source

I'm trying to visualise some data in a custom shape on a map, and I'm stuck with styling it. I'm currently using the openlayers framework in combination with a geoJSON file that I generate in code. ...
3
votes
1answer
409 views

Qgis analysis on polygon

I have a data table mapped and the table also contains further information of interest, beyond the lat/long of the specific data points. I want to be able to draw a polygon and then simply have a ...
11
votes
4answers
2k views

How to colour polygons with a completely transparent fill using MapServer?

Is it possible to fill polygons so that they are completely transparent in MapServer? I want to have a black background that is slightly opaque, and wherever there is a polygon I want that to be ...
1
vote
0answers
38 views

area weighted average for overlapping polygons [duplicate]

Possible Duplicate: How to use NASS county level crop data to estimate crop acreage in hydrologic regions? It seems like an easy problem but I don't know how to go about it. I have two ...
3
votes
2answers
823 views

How to filter out multipart polygons and then buffer?

I've written a small script trying to accomplish the task described in the question title. It basically looks like: in_fc = '...' # Some shapefile goes here # Get the fields (column names) of the ...
3
votes
1answer
2k views

Merging multipolygon data into a polygon

I have a MultiPolygon representation of some shapes in POSTGIS, I am trying to convert them to Polygon data. I tried, st_geometryn(r.geom, 1) but that didnt work because the way polygons are ...
1
vote
0answers
865 views

How to handle postgresql/postgis geometry type errors in a function?

I have created the following function in PL/SQL to make a polygon from a set of linestrings: CREATE OR REPLACE FUNCTION _myfunction( _fid integer, _rid integer ) RETURNS VOID AS $$ ...
4
votes
1answer
805 views

Extracting donut holes as separate layer in QGIS

Does anyone know how I can extract the holes in a polygon layer as a separate layer in Quantum GIS? An example could be a country with a number of lakes cut out of the polygon - I need the lakes. I ...
5
votes
1answer
2k views

Dissolving specific polygons inside SearchCursor with Python in Arcmap

I have a layer with catchment polygons. For those that are smaller than a certain size, I want to merge with an adjoining polygon (namely the one downstream). In the attribute table I have a GridID, ...
5
votes
2answers
912 views

How to combine data from overlapping polygons?

Here's what I'm working with: Shapefile of the current 32 Congressional districts for all states Shapefile of the tract boundaries for Texas A DBF format table of Hispanic counts and proportions for ...
3
votes
0answers
127 views

Why doesn't Polygonizer copy the line ids to my polygonized shapefile?

I am trying to convert a line shapefile into a polygon shapefile using Polygonizer plugin, and when my new polygons are created all the cells in my id field are "Null", although I have clicked "copy ...
3
votes
2answers
416 views

Determine density or cover from a raster layer that has been clipped by a polygon

I am a very new GIS user using ArcMap 10. I have a raster layer of tree canopy that I have clipped so that the layer is in a polygon that is a circle with a 2km radius. I have done this for four ...