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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480 views

How to do a spatial join if QGIS 1.8 keeps crashing?

I am trying to perform a simple spatial join (adding polygon data to points) in QGIS 1.8: target vector: points join vector: polygons take attributes of first located feature keep all records ...
3
votes
1answer
520 views

How to make a minimal distance matrix for polygons using QGIS?

I have a set of polygons and I want to find minimal distances between the edge of each pair of them. It's similar task as in this question: How to find the minimum edge to edge distance of polygons? ...
2
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1answer
422 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 ...
3
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0answers
191 views

How to estimate the average width of a sidewalk? [duplicate]

I have a table with two polygons representing urban block with and without the sidewalk: geomBlock and geomBlockWithSidewalk. On my city we can approximate the polygons of geomBlockWithSidewalk to a ...
5
votes
3answers
2k views

How to interpolate into polygons?

I need to interpolate values from points to polygons. I have a point shapefile and a shapefile of adjacent polygons. Some polygons get several points falling inside, some have nothing. I thought ...
1
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2answers
90 views

How to query points that fall outside their designated regions?

I have a shapefile with 250 points. Each point has a region attribute. In another shapefile I have all the possible regions with their names (it is polyline geometry). Unfortunately the coordinates ...
2
votes
1answer
992 views

How to convert a polygon to a grid of polygons using QGIS?

For example, the city of Rotterdam represented as a hexagonal grid.
5
votes
1answer
1k views

Export selected raster cells to polygon

I have selected certain values in a raster (roughly 1000 cells), and would like to export them to be able to create a polygon. Converting it to points first then to polygons does not work. Can anyone ...
12
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3answers
3k views

Proper way to rbind SpatialPolygonsDataFrames with identical polygon IDs?

What's the proper R idiom for rbinding SPDFs together when the IDs overlap? Note that here (as is often the case) the IDs are basically meaningless so it's pretty annoying that I can't just make ...
14
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4answers
3k views

What is the best open-source web mapping solution for handling 3000+ polygons

I have 3000+ polygons which represent watersheds (18 main watersheds). At the first stage all the 18 watershed will show and their list will be placed in the left sidebar. If any user mouse over the ...
3
votes
2answers
2k views

How to perform spatial queries on polygons in mongodb?

I will build a GIS system based on polygons, not just points. I wanted to use mongodb or postgis. how do this in mongodb? Query A - get the center of a polygon Query B - distance between two ...
3
votes
2answers
98 views

Splitting worldwide roads into multiple road datasets with less than threshold number of features?

I want to split a worldwide 'road dataset' into multiple grids/blocks-extents, depending on the amount of features resides in that block-extent. If the amount of features(inside that block) is still ...
9
votes
2answers
2k views

How to smooth large vector polygons from Raster

I have a landuse classification raster file (6 classes) of a large area. But I need it in vector polygons so I vectorised it. No problem so far, but the result is - of course - that every pixel is ...
3
votes
2answers
111 views

Selecting proper polygon

Currently doing a final project for school on ARCMAP 10. I have a set of unsuitable and suitable buffers over a big area which is Quebec City, Canada. The final potential sites give me areas between ...
2
votes
1answer
600 views

How can I get the corners of a polygon in latitude and longitude?

How can I get the corners of a polygon -a square/rectangle, to be precise- in latitude-longitude format by using its geom value -or some other way, perhaps-? Thanks.
0
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0answers
23 views

World country borders in polygon geometry format [duplicate]

Possible Duplicate: Where do I get territories data? Is there some source I can get all world countries polygon geometry points with latitude and longitude? I find it for USA states but ...
3
votes
3answers
2k views

How to digitize polygons from georeferenced raster file

I used QGIS to georeference a raster file of a custom US map. The map has features which are not strictly defined by state borders. I would like to digitize the map by creating contiguous borders for ...
2
votes
2answers
866 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 ...
1
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0answers
250 views

how to automate changing polygon's shape while keeping its area the same and limiting deviation from orginal centroid? [closed]

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, ...
3
votes
1answer
274 views

Area-weighted rasterising of polygon data

I'm looking for any GIS tool to do detailed rasterising of polygons. I've checked GDAL's gdal_rasterize command (and API), and ArcGIS's Polygon to Raster tool, but they only rasterise 1 attribute per ...
2
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0answers
601 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
842 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 ...
0
votes
1answer
488 views

In DIVA GIS how can I change the polygon co-ordinates of a .shp file?

I am using polygon layers from various sources to create species distribution maps however some of the layers have different polygon coordinates to others, therefore I cannot use them together as ...
4
votes
1answer
1k views

How do I split polygons that cross the dateline?

I have a dataset of country borders which I obtained from: http://thematicmapping.org/downloads/world_borders.php/ I have that dataset in both shp and SQL, but I'll put out there that I don't feel ...
0
votes
1answer
472 views

table of polygon centroids

Given a polygon layer, census tracts, how can I generate a table of centroid coordinates in QGIS, or add columns with the centroid coordinates or generate a new layer of polygon centroid points?
8
votes
3answers
459 views

Find Duplicate Polygons Algorithm

I have a group of polygons. My objective is to find the duplicate polygons from these group of polygons. Using NetTopologySuite(A c# port of JTS), it is possible to compare two geometires and check ...
4
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0answers
95 views

Reducing Polygons [closed]

I am merging several data sources into one final answer via a fishnet. My problem is I have landcoverage with multiple attributes unioned to a fishnet. Now I want to eliminate the smaller polygons ...
4
votes
3answers
962 views

How to split features?

I would like to split a shapefile in qgis according to how the polygons overlaps. Don't know how to though? See pic for explanation:
1
vote
1answer
263 views

What is the Quickest Way to Update Polygon Geometries in ArcGIS

I have a shapefile which contains the approximate boundaries for sites that are being worked on (thousands) in polygons, each with a reference number and additional detail in the attribution. I have ...
2
votes
1answer
844 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: ...
6
votes
1answer
336 views

Can you permanently set the polygon/polyline segment length?

I'm trying to create a several hundred polygons in ArcGIS 10, each of which may have up to several hundred vertices. For consistency sake I would like each line segment in these polygons to be of a ...
5
votes
1answer
836 views

Identify Polygons on raster image

I have OS street view mapping as raster images. Is it possible (without the obvious of tracing each dwelling) to identify all polygons on each tile. To clarify, My ultimate aim is to produce a ...
6
votes
1answer
2k views

Copy a polygon geometry in Arcpy

This to me sounded very simple so I am probably missing something basic here. What I need to do is to create a copy of a polygon shapefile to a new shapefile with slightly different attributes. Where ...
3
votes
2answers
1k views

How can i select a polygon in MS SQL 2008

I am very new to MS SQL 2008. I got a task to select a polygon from the polygon layer by giving the X-Y coordinates. I already got the script for PostgreSQL for the same thing, but i need it for MS ...
1
vote
1answer
223 views

How to identify Polygon within another Polygon layer

I have two polygons files. The first one has several smaller polygons within it eg.a shapefile with all US states, the other polygon file has a single polygon eg. a river basin. I am trying to get all ...
2
votes
1answer
751 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 ...
0
votes
1answer
449 views

To get attribute data of polygon layer by giving Lat/Lon

Is anyone having an idea about how to get attribute data of a polygon layer by giving Coordinates with in that polygon. Here i have tried with these codes.. SELECT * FROM kar_bbmp_198 WHERE ...
2
votes
1answer
979 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 ...
3
votes
1answer
541 views

QGIS Polygon layer table of adjacent polygons

In a polygon layer, how can I generate a table of adjacent polygons?
7
votes
2answers
11k views

How to calculate polygon areas and perimeters using QGIS?

Using QGIS, if I load a polygon layer and make a new column, how do I fill that column with the: area of each polygon and another column with length of the perimeter of each polygon?
8
votes
3answers
2k views

Creating regularly spaced, defined # of points within polygon in QGIS

I used the research tool "Regular Points" to produce a certain number of points within a polygon, but it forms a rectangular grid of points rather than only within the shape of the polygon. Since I ...
3
votes
0answers
60 views

Passing attributes to neighbouring polygons

I have an ecosystem polygon layer that has been updated using a more recent tree cover layer (to remove cleared areas and also to re-align veg boundaries where growth has occured). Where the polygons ...
0
votes
2answers
892 views

How can I convert Polygon to LinearRing Geometry?

How can one convert a Polygon to LinearRing geometry using OpenLayers? I'm thinking that I can do this by getting bounds of the polygon, then use this to construct a Points array. Finally, use ...
2
votes
0answers
212 views

Polygons of Land Use Change

I am doing a project where I am digitizing a map of Haiti from the 70s. Through R2V I digitized the lines and then I exported it into ArcGIS 10. I am just interested in the land use change, therefore, ...
6
votes
3answers
2k views

OpenStreetMap Neighborhood Boundaries

Is it possible to download neighborhood boundaries from OpenStreetMap? I see on maps that they often indicate neighborhood names; is there a way to retrieve their coordinates and boundary polygon ...
-1
votes
1answer
250 views

Finding the area of a polygon feature in a shapefile [closed]

Excuse the very simple question. How do i find the area of a selected polygon feature in a shapefile?
10
votes
1answer
648 views

How to convert fake donut holes in polygons to real ones?

I have this problem where I have to import shapefiles into our system which must be geometrically valid, but the software that everyone uses to produce them seems to output files where every polygon ...
5
votes
0answers
186 views

How to rotate polygon to find best fit in Mapnik? [closed]

I have a quite simple problem but somehow I just fail to solve it. There is a polygon and a range xsize and ysize. The x and y size determines the mapnik generated image. The polygon should now be ...
2
votes
2answers
596 views

Selecting Part of a Polygon

I have a dataset, in shapefile format, for agricultural land grades in England. It is divided into 7 categories in its attribute table. As the file is a large file and I only want a small section I ...
3
votes
2answers
2k views

How to change the vertex style for editing?

When I use drag feature, then the circles on the polygon edge has the same style. For example, this OpenLayers site. I need to change it, I mean they need to be a different color. What is their ...