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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How to stop or deactivate draw polygon control after the first polygon has been drawn in Openlayers

I want to only be able to draw one circle on my map and then disable the control. Below is my code, Any suggestions? <html xmlns="http://www.w3.org/1999/xhtml"> <head> ...
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1answer
1k 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 ...
1
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1answer
732 views

Aggregate Data between Polygons

I have data at the ZIP3 level and I need to join it to a state file. I also need the data within the zip3 file to be averaged, but for some reason when I use the join tools, i'm not getting the ...
4
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2answers
3k views

Is there an easier way to edit polygons in ArcMap?

I am updating woodlot polygons in ArcMap 10. Instead of editing individual verticies, is there a way to edit that is more like drawing part of a new shape (say if the woodlot has expanded only on one ...
2
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1answer
2k views

How to get the radius of a “circle” in Openlayers

How do you get the radius of a circle in openlayers? I have searched quite a bit and cannot find any resource for this. please help. Here is my code but I want the radius or circumference of the ...
2
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1answer
717 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 ...
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1answer
863 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 ...
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1answer
2k views

How to change events in the Oncomplete Drag function in Openlayers

below is code that works for Openlayers drag function: drag = new OpenLayers.Control.DragFeature(polygonLayer, { autoActivate: true, onComplete: function() {alert('Are you sure this is the ...
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1answer
361 views

Highlighting and exporting raster layer based on vector polygon

I am a Quantum GIS beginner. I have a set of adjacent polygons in a vector layer that is overlaid on a raster layer of OS StreetView OpenData. I want to be able to select each of these polygons and ...
2
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1answer
632 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: ...
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3answers
524 views

Selecting polygons by number of sides

I'm using ArcGIS 10 to build some figures for a journal article. One is a figure of an unstructured finite element mesh of triangles spanning the western Atlantic Ocean. I exported this mesh from ...
3
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1answer
1k views

Transform polygon to equivalent circle, QGis

I have a polygon and I'd like to find the radius of an equivalent circle from a particular point within the polygon. The polygon would have a large (infinite) number of points evenly distributed ...
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2answers
3k views

How can I fix my complex Polygons so they show correctly in Google Maps?

Problem: I'm trying to find a way to fix some broken polygon shapes and I'm not sure how I can do this. Details: I've got a number of polygons which I basically imported from TIGERLINES a while ...
6
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1answer
2k views

How to calculate the size of a particular area below a buffer in QGIS

I have a point shapefile of villages where data was collected in Northern Kenya. I created a buffer around those villages. The second vector layer contains polygons defining areas according to ...
2
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2answers
3k 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 ...
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1answer
402 views

Splitting raster pixels by a polygon's edge?

I have a a polygon shapefile of different regions, and a raster grid of precip data. I want to take the polygon and add up all the raster precip data in each zone. I could use zonal statistics to do ...
4
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1answer
4k views

How to select and copy a group of polygons in QGIS?

I'm new to QGIS. I opened a few shapefiles that cover Europe. Now I want to select a smaller area and if possible copy the polygons in this area so I can work with a smaller set. How should I do this ...
6
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1answer
1k views

How to persist a polygon to SQL Server database and vice versa?

How do I extract all the points from a Polygon drawn in ArcMAP and then persist that data into a SQLServer database table containing a geometry column and then when I've got the data persisted read ...
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3answers
2k views

How to select the vertices from a polygon?

I am writing some VBA code to extract vertices from a polygon. I would like to ask, how to select the vertices from a polygon ? Regards Gary
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1answer
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Should I split MultiPolygons into Polygons?

In the system I'm implementing I have a table T1 with an associated geometry. Most of the geometries are a set of n polygons, with 10 < n < 100. At the moment in the table T1 I have a geometry ...
5
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3answers
2k views

How can I display with OpenLayers the geometry returned from a ST_Buffer in POSTGIS?

Im using PostGIS, GeoServer and OpenLayers, and the thing is that i want to display the geometry result from a query like this: SELECT ST_Buffer(ST_GeomFromText('POINT(100 100)'), 500); To perform ...
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1answer
1k views

How to create a polygon from other polygon boundaries?

I want to write an algorithm that creates a polygon inside a hole made by a set of other polygons. It's something like a flood fill and it's like the "boundary" tool in Autocad. The image shows an ...
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2answers
5k views

ArcObjects - Finding the intersection of a polyline and polygon?

I have a polyline and polygon. The polyline will intersect the polygon at two or fewer points. I would like to get these intersection points as X and Y values. EDIT: Here is a quick code sample using ...
3
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1answer
309 views

Polygon Shared Boundaries in GML

Last week I was told on a phone conference that GML supports shared boundaries in Polygon's. I have been unable to find any documenatation to substantiate the claim. Here is the situation: I have a ...
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2answers
1k views

Resize polygon along one axis

Using the following example I'm able to resize by scale and origin. polygonFeature.geometry.resize(scale, origin); vectorLayer.redraw(); But does anyone have any suggestions or sample code ...
4
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3answers
9k views

How can I calculate the center point inside a polygon in ArcGIS 9.3?

I'm using the JavaScript API 1.6 on ArcGIS 9.3. I have a polygon geometry in an ArcGIS map, and I'm trying to find a way to get the point that lies in the exact center of the geometry. What is the ...
3
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4answers
390 views

Creating Polys and Displaying geo points within. ( Where to start? ) [closed]

Hey all, I'm somewhat of a newb when it comes to creating mapping solutions. I've stayed on a pretty high level playing with openlayers and pulling data from various webservices. The first part of ...
16
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4answers
1k views

Why do valid polygons repeat the same start and end point?

In the GIS world, for most modern formats and Standards (e.g., Shapefiles, WKB/WKT, GML, KML, etc.), valid polygons need to have closed linear rings, which is a linestring of coordinates where the ...
6
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2answers
3k views

Openlayers geometry: how to convert area from degrees to square kilometres?

I get a multypolygon from my web service and want to calculate the area of that polygon. I was trying to use this piece of code: var poly = new OpenLayers.Geometry.MultiPolygon(poligon); var area = ...
3
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2answers
5k views

Label *beside* polygons in ArcMap 10?

I try to add labels to polygons in ArcMap 10 based on a field in the corresponding attribute table. However, the labels always appear inside the polygon, and I can't find an option that lets me put ...
1
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0answers
100 views

Getting started with storing LoST and GML searching

I am working on a logging and search database application. The application will receive event records containing XML LoST values (RFC5222 Location-To-Service-Translation). These records will be ...
10
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3answers
868 views

Polygons from Polylines in either ArcView or FOSS

I have 20,000 polylines in a .gdb that represent about 5,000 building footprints. Some of the building footprints have pretty substantial gaps (image below). I would like to snap the polylines closed ...
3
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3answers
8k views

How to create a polygon buffer from a line?

I have connected a series of points into a line in ArcMap 10 with the Points to Line tool in the ArcToolbox. The line is, of course, in its own layer, and I added a 5 meter buffer around the line. It ...
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5answers
3k views

Algorithm to find polygons enclosing points

I'm trying to find an algorithm that can determine the smallest possible polygons to cover a number of points. I know how to get the convex hull around all the points, but say that the points are ...
3
votes
2answers
284 views

Search for Multiple Polygons in ArcMap

Is there a way to do a search for features that occupy more than one polygon in ArcMap? I am working with a Parcel layer, and there are some cases where the parcels will take up multiple polygons (...
4
votes
1answer
5k views

Converting tax map polygons from Shapefile to table of map number and corner coordinates

Fairfax County, Virginia provides a Shapefile here which shows the boundaries of the tax maps as polygons. Each polygon simply consists of four corners, and what I'd like to do is create a table ...
10
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2answers
1k views

PostGIS: split a polygon in a given ratio

Is there a convenient way to split a polygon into n parts, more-or-less equal in size in PostGIS?
2
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2answers
588 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 algorithm....
8
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2answers
762 views

Splitting polylines using regions with PostGIS

I was wondering if it is possible to split a polyline on polygon boundaries (regions) in PostGIS, the picture below is of what we have at the moment and showing where I need the polylines split: ...
0
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3answers
250 views

How illustrate cells in attribute table?

Firstly, many thanks to all of you who have been helping me greatly, just can say THANKS. Secondly...I have a new question. I have an attribute table with 2883 rows which are the OA of Leicestershire ...
8
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4answers
6k views

Best way to delete selected mass amounts of old data from a polygon shapefile attribute table?

Dumb problem that for some reason is giving me trouble. I have a polygon shapefile that is loaded with old demographic data in its attribute file, I just received the new data today in xls format. ...
28
votes
4answers
8k views

Separate polygons based on intersection using PostGIS

I have a PostGIS table of polygons where some intersect with one another. This is what I'm trying to do: For a given polygon selected by id, give me all of the polygons that intersect. Basically, ...