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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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 ...
6
votes
1answer
742 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 ...
6
votes
1answer
3k 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 ...
6
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3answers
2k views

Can Polygons be generalized to MultiPolygons in GeoDjango?

I set up a model with models.PolygonField in geodjango, using postgres as database. I try to import shp into postgres. The problem is, shp (compiled with QGIS) mixes polygon and multipolygon, hence it ...
6
votes
2answers
564 views

Wrong $area from field calculator (QGIS)

The area of the polygons in a layer, calculated by the field calculator with "$area" is wrong (much too big) for some polygons. If I draw the concerned polygon again, the area is calculated correctly. ...
6
votes
2answers
9k views

Createing polygon layer from point data using QGIS?

I'm currently using QGIS 1.8.0 I would like to create a polygon layer from a point dataset, where the size of the polygons relates to the resolution of the grid reference. The ultimate aim would be ...
6
votes
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 ...
6
votes
1answer
9k views

Calculating line segment lengths within polygon using ArcGIS Desktop?

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 ...
6
votes
1answer
490 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 ...
6
votes
1answer
536 views

How to draw shapes with highest possible decimal accuracy

I am trying to read input of lat and long to draw the shape based on condition.The input is standard array of lat and long with 15 decimal accuracy. I am realizing - I am loosing some decimal accuracy ...
6
votes
1answer
7k views

can I extract overlap of polygons within the same layer?

I am trying to extract the overlap of polygons that are within the same layer in 10. The layer came from a buffered street centerline and I'm trying to extract and delete the intersections from the ...
6
votes
2answers
3k views

Count number of unique raster pixels in polygon using ArcMap?

I have a polygon shapefile and I want to generate a table of a count for each pixel value in each polygon. My main goal is to find out what pixel is most abundant in each polygon. I am using ArcMap ...
6
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1answer
1k views

Creating Multi-Part Polygons that touch internally using ArcGIS for Desktop?

I have a set of parcels as illustrated in the image below. There are currently no multi-part features in dataset. What I would like to do is to merge (not the right word) all of the parcels with same ...
6
votes
1answer
2k views

Identify polygon overlaps within single shapefile

Using either QGIS (1.9) or ArcInfo (9.3.1) I'm trying to identify unique overlaps of prehistoric building footprints from an archaeological site recorded within a single polygon shapefile. While the ...
6
votes
2answers
1k 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 ...
6
votes
1answer
324 views

Select by location of doughnut hole polygon

I have vectorized the Corine Land class raster and want to select certain classes that are "inside" other classes. How can I select the polygons circled in blue? All the select by location options ...
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 = ...
6
votes
1answer
105 views

How to make a wedge shapefile in R?

I'm quite okay at R programming, but fairly new in GIS (especially in R). I have a set of coordinates and I'd like to create a custom shape around them. What I want to do step-by-step: Create a ...
6
votes
3answers
669 views

adjusting polygons to boundary and filling holes

here's the problem: Where: 1: department boundary 3: polygons inside department boundary that "touch" the department boundary(1). They are not necesary fitting well inside 2: holes between 1 and ...
6
votes
1answer
846 views

POSTGIS SQL - How do I remove (defined) sliver polygons

I would like assistance in writing SQL (for POSTGIS in postgresql) to remove sliver polygons (including long narrow slivers and some small irregular polygons that were erroneous 'gaps' in the original ...
6
votes
1answer
93 views

Is there a way to select only a certain polygon for editing?

I have a spatialite data base with 4300 polygons contained within. I wish to be able to edit the polygons but once i have highlighted the Polygon from the attributes table i find it hard to edit the ...
6
votes
1answer
671 views

Generalize large polygon-file

I have a large polygone file with landuse information (6 classes). Its vectorised from a raster classification so the polygons are all angular. Any of my tries to generalize with v.generalize (sneaks, ...
6
votes
4answers
366 views

Filtering features using geometric attributes of polygons in ArcGIS Desktop?

Given a polygon featureclass containing many polygons of different sizes and shapes, which geometric attributes (area, perimeter, etc) could be used to filter the polygons? It's probably best to ask ...
6
votes
1answer
433 views

Permanently setting polygon/polyline segment length using ArcGIS Desktop?

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 ...
6
votes
0answers
720 views

How to split polygons without ArcView? [closed]

I'm trying to split polygons into equal areas. While fishnet sort of works; the areas I'm trying to split don't touch; they're national parks. Fishnet spans the whole area, not just the polygons in ...
5
votes
4answers
3k views

Is there a way of auto_increment for the ID column in QGIS

I'm creating a fictive map and so I need to create lots of points, lines and for sure polygons. Later on I export my data as geojson. But before that I aways have to go and give every element an ...
5
votes
2answers
145 views

Are there any multipolygons in my shapefile?

In QGIS 2.x, is there a simple way to determine if a polygons layer contains multipolygon geometries and if yes: which are these features?
5
votes
4answers
17k views

QGis: Merge intersecting polygons into one which are part of the same feature

I'm not a GIS professional so I hope I use the correct wording, at least I hope you understand my question. Let's say there are 5 polygons in the feature A. In the shape file there are more features....
5
votes
4answers
84 views

How to change feature draw order in QGIS?

Probably a very basic question here, I want to change the draw order of a shapefile in qgis, how can this be done? As you can see in the picture below, only the "10" layer is shown, but since this ...
5
votes
2answers
5k views

Converting Longitude and Latitude Coordinates to Square Miles?

I have a set of Long and Lat co-ordinates making up a five point polygon which I have converted in excel using the following formula: =((X1*Y2)-(X2*Y1)+(X2*Y3)-(X3*Y2)+(X3*Y4)-(X4*Y3)+(X4*Y5)-(X5*Y4)+...
5
votes
4answers
2k views

UK Postcode boundaries [duplicate]

Before I go and pay is there a free source for UK Postcode Boundaries, ideally down to Postcode Sector level ("AA00 0" or even better "AA00 0A")? Failing that can I generate them in QGIS if I have ...
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
8k views

How can I display this polygon in Google Maps, properly

NOTE: this question is sorta like a follow-on question to this original GIS Question I asked. In that question, the main suggestion was that I was trying to show two polys. Now, I'm asking about a ...
5
votes
2answers
195 views

Find lower left corner of a rotated polygon

I am currently struggling with a mathematical problem and can't seem to get it solved. I have a bunch of rotated rectangular polygons (solution should also work for non-rectangular polygons) in ...
5
votes
3answers
950 views

Creating map with same-area hexagonal polygons using ArcGIS for Desktop?

I'm trying to figure out (1) what this type of map linked here is called (I've been unable to find the name through search), and (2) whether there is an Arc tool that will transform a shapefile or ...
5
votes
3answers
5k 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 ...
5
votes
1answer
1k 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 ...
5
votes
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 ...
5
votes
3answers
142 views

Merge a list of spatial polygon objects in R

I have a list of spatial buffers (30000 buffers) that I built with the function lapply: buff.pts <- lapply(1:nrow(pts.prj), FUN=function(l){ buff <- gBuffer(pts.prj[l,], width=1000) ## 1km ...
5
votes
1answer
3k views

Extracting intersection areas in R

I have two polygons. One contains fields(X,Y,Z) and the other contains soil types (A,B,C,D). I want to know what area of every field contains which type of soil. I tried the following: library(...
5
votes
4answers
4k views

Clip raster using shapefile into multiple rasters using ArcGIS Desktop?

I have a raster file representing a large area and a shapefile of 30 polygons representing watersheds. I would like to clip the raster with the shapefile to create 30 rasters representing each ...
5
votes
2answers
775 views

inner convex-hulls in a set of 2D points

A set of 2D Points are scattered randomly (i.e., no specified pattern), we are interested in finding all inner-convex-hulls (ICH) in an order of largest in area to a minimum until the entire study ...
5
votes
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 ...
5
votes
2answers
130 views

How to sum attribute values for areas where multiple polgons overlap?

I have one shapefile with many polygons (at least 100). Each polygon has a value. Almost all these polygons overlap with each other. I want to sum the values of the polygons in the overlappings depend ...
5
votes
3answers
124 views

Dissolve overlapping polygons in SAGA

I've got the following (2D!) situation of overlapping polygons: I would like to have the polygon border dissolved such that I have only one polygon left. I thought this was a definitive case for ...
5
votes
1answer
2k views

calculate {minimal} distance between polygons in R

I have calculated the surface area of species distributions (merging polygons from shapefiles), but since this area can be comprised of quite distanced polygons, I would like to calculate some measure ...
5
votes
3answers
5k views

Intersect (analysis) of polygons generating empty output

I have previously asked a question on determining the area of polygons with another polygon boundary. Determining the area of each polygon within a polygon boundary? I came to the conculsion that ...
5
votes
2answers
1k 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? ...
5
votes
3answers
3k views

How to interpolate into polygons using ArcGIS Desktop?

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 ...
5
votes
1answer
90 views

Clipping features depending upon percent coverage by other features

I have a shapefile composed of several thousand square polygons of equal size, arranged in a grid. I have another shapefile with a few dozen circles. The squares are about 1/10th the size of the ...