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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399 views

Locating the centroid (center of mass) of spherical polygons

I'm trying to work out how best to locate the centroid of an arbitrary shape draped over a unit sphere, with the input being ordered (clockwise or anti-cw) vertices for the shape boundary. The density ...
3
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4answers
1k views

QGIS Polygon precision

Is there a way to edit the precision of polygon points in QGIS so that each coordinate has the same number of decimal places? For example, the coordinate 23.18273917, -84.29172638491 would be ...
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1answer
1k views

How to narrow the result from Nominatim with only cities and countries, no additional areas with the same name?

I'm trying to get WKT or GeoJson polygons of cities and countries from Nominatim (for example, Paris and France). I send a GET request but it returns me several results named "Paris" or "France". How ...
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3answers
2k views

How to get WKT or GEOJson by country or city name with Overpass API?

I'm trying to understand Overpass API, I'm experimenting with it, but cannot get what I expect. Overpass API doesn't return me neither polygon shapes, nor WKT, nor GEOJson, nor even a highlight of the ...
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3answers
2k views

How to get a list of OSM relations (id numbers) of cities and countries only?

I want to get OSM polygon shapes (GEOJson or WKT) of countries and cities only. I know that it is called a "relation" in OSM and each relation has its own id (New York is 175905, for example). How may ...
3
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3answers
772 views

Determining the area of each polygon within a polygon boundary?

I have a series of maps representing a 1000m diameter around a point. These maps contain 40 different types of polygons that represent a land use (ex. Corn crop, Pasture). I want to select all ...
1
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0answers
280 views

Line features into polygon features

Can any one tell me how to convert line features into polygon features in ArcGIS. I am using ArcGIS 10. I searched the arc toolbox for any tools for this conversion, but I couldn't find any. Please ...
2
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1answer
307 views

Heads up digitizing - Polygons overlay differently with two different Satellite images

I have been digitizing building footprints from satellite image using ArcGIS 10.1 . Field data collections is done with the use of four corner point GPS way point. Due to multipath errors, we are ...
1
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2answers
484 views

Calculating minimum/maximum width for overlay of two polygon strips in ArcGIS or some Opensource GIS

Is there some solution for calculating minimum and maximum width for overlay of two polygon strips? When I clip these strips the result is another strip with variable width about 1 km and 20 km long. ...
2
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1answer
32 views

Selecting Polygon Features in QGIS Lisboa

I want to select and save as a separate shape file, a smaller section (polygon) from a whole island country which includes both land and shallow habitat coastal features (like coral reefs) and when I ...
1
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1answer
83 views

Generating vineyard's rows in a polygon

Does anyone know if it's possible to generate line (the distance between each one is 2 meters) in a polygon?
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2answers
1k views

Simple way to detect/select border polygons of a shapefile

I am looking for a simple way to detect/select border polygons of a shapefile. Border polygons are here polygons that are not completely surrounded by other polygons i.e. polygons located at the ...
3
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1answer
410 views

Postgis identify points on the polygon border

I have points geom in gid,pt_geom and polygon geom in gid,pl_geom. Some of the points are inside polygon and some are outside polygon, others are on the polygon boundary. Is there any way to ...
0
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0answers
31 views

calculating mean and standard deviation for raster values using whole pixels within a polygon [duplicate]

i have a raster image and a corresponding shape file. i would like to calculate the statistics of the values within polygons which have a common attribute but only using pixels which are fully ...
1
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1answer
576 views

Drawing polygons with Google Maps using local shape data

I am trying to draw a census tract on a Google map. It looks like Google Maps lets you draw polygons using longitude and latitude coordinates. However, the data that I have is not longitudes/latitudes....
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0answers
78 views

When digitizing, polygons are inverted

I need to use QGIS to digitize my images. My images are scanning electron microscope (SEM) images of rocks. I am interested in analyzing the pore space in the images. Here is the steps I follow: I ...
7
votes
3answers
818 views

Lossless Polygon Simplification?

Is there a standard/recommended algorithm for simplifying a polygon without shrinking any of its original boundaries? Right now I'm using TopologyPreservingSimplifer within JTS and running into ...
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3answers
954 views

“Identity” overlay in QGIS?

I have two polygon layers I'd like to overlay using QGIS or another open source tool. What I want as output is a polygon layer with the extent of one polygon, but with each polygon in that layer ...
1
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0answers
761 views

How to get polygon coordinates for Google Map from .poly files (preferably in nodejs)?

I have .poly files with polygons of countries. I want to use those polygons to make Google Map polygon layers. How may I read lng and lat points of polygons from those poly files? They look like these:...
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1answer
1k views

ARCGIS 10- Cutting down a tiff file layer to a smaller polygon?

I have a dynamic land map featuring open forest, closed forest ect of an area which is a tiff layer file. I want to be able to cut the layer file to my area of interest, the polygon I created? I also ...
1
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0answers
63 views

Delete polygon underlap?

I am editing a layer in QGIS with severe polygon overlaps. Is there a way to delete the underlapping portions (i.e. the invisible parts) using QGIS? If I import the layer into GRASS using the GRASS-...
4
votes
1answer
162 views

Postgis 2.0 geographic polygon has max longitudinal range

My problem is that I have a load of geographic point data (srid 4326) in a table. A user may do a bounding box search - essentially create a polygon as follows: l_poly geography(Polygon,4326):= '...
4
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1answer
470 views

intersection between two multipolygons yielding anomalous GeometryCollection object full of LineString's & Polygon's (trying to get intersect area)

Normally when I call the #intersection method on a multipolygon to find the intersection shape on another multipolygon I get a multipolygon returned back to me. Either that or something else I can ...
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1answer
713 views

JTS Polygon simplification without holes

I have a set of polygons without holes. I wish to merge any intersecting polygons. I don't want to have any holes in my simplified polygons. Is there a recommended way to achieve this using JTS? The (...
5
votes
1answer
602 views

Create MultiPolygon from QgsGeometry.fromMultiPolygon

I have a list of polygons' points like [[x1,y1],[x2,y2],[x3,y3],[x4,y4]] [[x5,y5],[x6,y6],[x7,y7].[x8,y8]] now I want to create multipolygon from it by using feature = QgsFeature() feature....
9
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2answers
3k views

How to remove small “salt & pepper” polygons from a layer?

I have a map made up of multiple polygons, with a few hundred thousand points very small polygons on within it. I need the larger polygons, but not the points small polygons. How do I select and ...
8
votes
4answers
22k views

How to Merge/Dissolve Polygons By Common Attribute Field in QGIS?

I have joined corresponding Local Enterprise Partnerships table data into a polygon shape file containing UK Local Authorities. How do I Dissolve or Merge the the Local Authorities polygons by ...
1
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0answers
61 views

Dissolving overlapping polygons - issue in QGIS [duplicate]

I have the OS Code-Point map which I want to dissolve into the regions that my company use. I have used the dissolve function in QGIS, but it is having a problem where a vertical street overlaps with ...
1
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1answer
146 views

How to find out to which polygon each points belongs to?

I have searched for an answer to this, but couldn't find anything useful. I have got a shapefile consisting of a number of polygons, and another shapefile with a number of points. I want to add a ...
1
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2answers
309 views

QGIS point sampling tool really slow for polygons?

I have a large field of randomly distributed points (100,000 of them to be precise), and I'd like to get values for a variety of raster and polygon coverages for each point. I've been using the QGIS ...
4
votes
1answer
128 views

What is the best format to encode polygons such as lakes?

I am looking for a standard format to encode polygons, such as lakes, in one file that is easy to create and common so that others can use it in different GIS systems. Every file will contain data on ...
4
votes
4answers
1k views

Creating polygons as % of original area using ArcGIS Desktop?

I have a polygon shapefile and need to create new polygons, within the originals, as % of original area. I used buffer by field (Field= new area as %) but the buffers are created in circles around ...
1
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1answer
2k views

Get Features from OpenLayers Layer.Vector not working

polygon_layer = new OpenLayers.Layer.Vector("Polygone", { projection : projLonLat, strategies : [ new OpenLayers.Strategy.Fixed() ], protocol : new OpenLayers....
4
votes
4answers
2k views

How to import polygons from OSM to QGIS?

I am trying to import Polygons from OSM to QGIS 2.0, but so far I have no idea how to do that. E. g.: Kisterseg auf Tatabanya in HU: http://www.openstreetmap.org/?relation=1027806 Is there any fast ...
2
votes
1answer
520 views

Merge Two Polygons Using Editor merge in arcGis

i want to create a ArcEngine function using .net that allow to do the same thing like (see picture): select 2 polygons click merge Is there somebody who can help please!! Sincerely
2
votes
1answer
603 views

Convert polygons to KML file

I have a set of polygons out of which I want to make a KML file, my table schema is as follows : CREATE TABLE [dbo].[utilitygeo]( [ID] [int] NOT NULL, [PolygonID] [varchar](8000) NULL, [...
0
votes
1answer
94 views

Openlayers selection

Is it possible to select a polygon from a predefined Lat & Lon programmatically? eg location point: x='1234' y='5678' intersects polygon '1234', therefore SELECT POLYGON '1234' So far I have ...
1
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1answer
577 views

Intersection of multi-polygons in postgis

How can I get the intersection of 3 multi-polygons in postgis? I have three geometry collection and I want a fourth with the result of intersection of the other three. GEOMETRYCOLLECTION(MULTIPOLYGON(...
1
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1answer
89 views

What is the best public geoservice for getting data about buildings?

What is the best public geoservice for getting data about buildings, which is free? Or maybe it's better to ask "does exist such a public service?" I want to add some 3d polygons to my 3d plane, ...
0
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0answers
48 views

Polygon shading is darker in certain areas

When drawing in qgis i am encountering an error when drawing large polygons snapped to multiple points. Polygons that have this shading in certain areas are not displaying correctly in other ...
1
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0answers
141 views

Free cartographic texture resources

I've been trying without success to find free textures to use in TileMill. I'm looking for fairly simple, abstract textures, like a dotted pattern (to indicate national parks). Are there any well ...
2
votes
1answer
719 views

QGIS: CSV point grid to polygon - not raster

I have a CSV file with various data in 1 degree wide by 0.5 degree high rectangles, for which I have the N,S,E,W, & centroid lat/longs, i.e. every bit of spatial data required. I'm trying to ...
7
votes
2answers
5k views

Dissolve polygons in QGIS (GEOS) with tolerance

I have a polygon vector layer representing the area inundated in a flood. The layer has been produced in a such a way that some of the areas are composed of multiple smaller touching polygons (see ...
1
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2answers
555 views

how to set width & height of a polygon in QGIS

I can't setting width and height of a polygon How to do that in QGIS? Thank you
2
votes
2answers
1k views

How many interior and exterior rings can a polygon have in a standard ArcGIS shapefile?

working with GDAL/OGR library and studying these two slides about geometries and vector data in the OGR library: slide 1 slide 2 I found that a polygon can have an exterior ring and lots of ...
1
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2answers
226 views

Integrate grid and polygon of municipalities keeping the biggest municipality per cell with QGIS (or another)

I have a 9x9 grid and a polygon of municipalities of an extensive area of Brazil. My goal is to have a field indicating the biggest municipality per grid cell. I've been trying with intercept without ...
7
votes
1answer
213 views

Find and destroy duplicate OSM multipolygon/polygons in TileMill/PostGIS

In OpenStreetMap there are sometimes multipolygons where attributes are present on both the polygon and the multipolygon relation, such as the Grampians National Park: http://www.openstreetmap.org/...
1
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0answers
118 views

level of spatial aggregation of polygons

I am looking for a method that allows me to obtain the spatial aggregation of polygons for each cell of a grid with 10kmx10km resolution. In each cell (10kmx10km), I want to be able to consider that ...
1
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0answers
294 views

Divide polygon based on points for even distribution

If I have a point layer, how can I create a polygon that includes all of the points and divide that polygon into n sections in which each section contains an equal number of points? Preferably in QGIS,...
3
votes
2answers
838 views

Finding points along a path

I am unsure of the best approach to this problem. I can think of some ways of doing it which I will list below but I am looking for the best and most efficient way of doing this. Problem Given a ...