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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4answers
1k views

Remove Polygon Islands

I'm really stumped with the problem. I have a polygon layer with no intersects or holes and I need to remove some 'islands', as defined by attributes of a certain size within the layer. It's a hard ...
4
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2answers
9k views

Combining adjacent polygons sharing a similar trait into 1 polygon - ArcGIS

I feel like this is a fairly novice question, but unfortunately I can't seem to find the answer (don't think I'm searching using the correct terms). I have a large dataset of habitat classes which I ...
4
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3answers
798 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 ...
4
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1answer
1k 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 ...
4
votes
2answers
740 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 ...
4
votes
3answers
220 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, ...
4
votes
1answer
3k views

How to smooth/generalize a polygon in qgis

Is it possible to smooth or generalize a polygon in qgis? Ìs there a plugin available like the generalizer-plugin for lines? I could convert my polygons to lines, smooth them and convert them back to ...
4
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3answers
930 views

How to Clip a Vector File based on certain Raster Values?

I need to clip a vector file based on certain values of a raster (Slope > 2%). I can´t find a direct way to do it. Trying to vectorize the raster first didn´t work. Is there any tool (ArcGIS or ...
4
votes
1answer
1k 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 ...
4
votes
1answer
2k 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 ...
4
votes
2answers
531 views

How to include polygons as part of a network for Network Analyst (ArcMap)?

I am creating a pedestrian walking network of a downtown area. I am digitizing line segments for paths and sidewalks, but I need to incorporate parking lots into my analysis. So far, I have been ...
4
votes
1answer
111 views

ArcMap 10.1 SP Spatial Join Problem (lines within polygon)

I have a line layer (faults) and a polygon layer (fishnet grid). The fishnet has a risk of earthquake attributed to each polygon. I want to take that risk value and give it to the fault lines which ...
4
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2answers
283 views

How do I find the average distance within a polygon to a point?

For my purposes, I can assume a homogeneous distribution of points within the polygon. What I want to find is the average distance from points within a polygon to a specified point. I don't know where ...
4
votes
1answer
354 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 ...
4
votes
1answer
395 views

Iterate features on SpatialPolygonsDataFrame in R

I have a SpatialPolygonsDataFrame object. Is there way to use apply on this object rather than using a for loop to iterate features in this object?
4
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3answers
722 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:
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votes
2answers
458 views

Is it possible to generate a vector polygon from a polygon on a raster image?

I have a raster map which I have extracted from a government report providing flood extent return frequencies. I want to 'snatch' these flood extent polygons (i.e. convert to vector) and I was ...
4
votes
2answers
2k views

Arcgis: How to find polygons within a polygon?

I am new to GIS and ArcGIS. I have a problem I need to solve: I have a set of polygons, some of which enclose other polygons. They are lake polygons, and within lake polygons, are smaller island ...
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3answers
6k 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 ...
4
votes
1answer
166 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() ...
4
votes
1answer
189 views

Raster to vector with gaps in Landsat ETM

I need to find size of water area from a raster (jpg) using QGIS 1.8.0-Lisboa. The raster is a Landsat image with gaps of data in it. I used Polygonize, but the output file shows wrong polygon size ...
4
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1answer
303 views

Sub-dividing a polygon into smaller polygons

In OpenStreetMap data, some large areas are tagged with a residential=yes tag. Actually within this large polygon there are multiple smaller (rectangular) houses (which are actually not drawn as yet). ...
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4answers
311 views

How to computational efficiently check if there are any overlapping polygons in a group of polygons?

I need to do some processing with groups of polygons. If any of the polygons in the group overlaps other polygon the result is unpredictable and don't throw any error. So, I need to detect if there is ...
4
votes
1answer
201 views

Splitting polygons leaves null values

I'm trying to split polygons with overlaping line features, using Split Polygons tool from Topology toolbar. The problem I encounter is that only one from new polygons have old attributes and others ...
4
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1answer
2k views

Arcgis 10: Point layer, polygon line layer, draw points to the nearest polygon point or other nearest line?

I have been using arcGIS for a while now but I often get frustrated with it :( I have version 10.0 arcGIS and I'm have two layers 1) Point data (building locations) 2) a polygon shape file (outline ...
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3answers
970 views

Calculate neighborhood statistics for polygons?

I've been searching around for the answer to this (including here) and have yet to find it. I'm interested in finding out how to calculate a 'neighborhood sum' for vector, polygon data. I am aware ...
4
votes
1answer
1k views

Create overlapping polygons from contour lines

Working in ArcGIS 10, I have a set of contour lines representing density of commercial square footage, and I have a set of points representing local maxima for each peak of the dataset. For each ...
4
votes
1answer
930 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 ...
4
votes
2answers
87 views

Converting shapefile to raster: Character attributes

I've got a shapefile that I would like to convert into a raster, but the trick is that the attribute I want a raster version of is character data. I'm familiar with geoprocessing using GDAL (in the ...
4
votes
1answer
88 views

Merge polygon without attribute (in field) with nearest polygon with attribute

In the image you can see districts in BLUE with attributes (name of district) and small pieces in RED. The red polygons belong to the blue and I want to merge them. The RED are only towards the ...
4
votes
1answer
354 views

How to split a polygon using R

I have an irregular polygon which is a spatial object. I want to divide it into multiple polygons (say, n=25) with equal height. To show how I want to divide it, I've plotted grids on the ...
4
votes
1answer
599 views

How to automate the drawing of polygons (square) around a number of points in QGIS?

In QGIS (or alternatively any other scripting + GIS stack), how can I automate drawing a 100km x 100km square around a number of points, with the point being dead in the center? I'd need to loop ...
4
votes
1answer
1k views

GDAL - creating vector from raster

[SOLVED] Good day! I'm looking at either gdal_contour or gdal_polygonize.py to create a vector layer file from a raster file. I can create the vector file using either method, but it's upside down ...
4
votes
1answer
2k views

Convert shapefile lines to a polygon in GRASS

I have a shapefile of a map that is the outline of a number of islands. I would like to convert the lines into polygons (ie all islands filled in) using GRASS. I searched on how to do this with GRASS ...
4
votes
1answer
120 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 ...
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0answers
141 views

Cut polygon and retain data

I have these two polygons: library(sp); library(rgeos); library(maptools) coords1 <- matrix(c(-1.841960, -1.823464, -1.838623, -1.841960, 55.663696, 55.659178, 55.650841, ...
4
votes
1answer
355 views

MongoDB: Search for polygons which have a certain location

Good day :). I am trying to implement a search feature on MongoDB using Mongoose.js , the short version of which is this: I tag locations on a map as polygons. and give them names. Then when an user ...
4
votes
0answers
288 views

Rgeos drops associated values when intersecting polygons

I am trying to intersect two SpatialPolygonsDataFrames and get a SpatialPolygonsDataFrame as the result. Unfortunately, using the gIntersection function from rgeos (which works impressively quickly ...
4
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0answers
85 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
0answers
241 views

How to write a script to square polygon corners?

I'm looking for a script that will square the corners of polygons that are near 90 degrees but not exactly. Near could be dealt with via a variable, for example within 5 degrees of 90 (85 - 95 ...
3
votes
5answers
1k views

Simplify shapefile parcel layer

I have a very large shapefile with over a million parcels within it. The problem I am having is that the polygons representing each parcel are very jagged. What I am looking for is a simple and fast ...
3
votes
3answers
304 views

How do I sort polygons by their 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 ...
3
votes
2answers
1k views

How to edit Shapefile Attributes?

How might I go about exporting a polygon shapefile (e.g. CSV) so that attributes (not geometry) are editable by others, and importing it with the changed attributes (of which there are several columns ...
3
votes
2answers
149 views

How to Select “Inverse” of intersection of two polygon layers?

I'm wondering if there's a way to intersect two polygon layers, take the intersection, and remove that from one of the polygon layers, making a new layer out of whatever is left over? Basically, the ...
3
votes
2answers
1k 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 ...
3
votes
2answers
4k 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 ...
3
votes
1answer
408 views

How to add CSV data with no coordinates to a polygon layer in QGIS?

I would like to add attributes from an spss database (around 300 cases) to a polygon layer in QGIS. Both datasets have a column with unique IDs. I exported the spss data to a CSV file which does not ...
3
votes
1answer
737 views

How can I get my Qgis area calculations in metres rather than degrees? My shapefiles are projected using WGS 1984 UTM fuseau 35 Sud

I am using Qgis 1.7.4 to calculate the area of polygons. My shapefiles have been projected using the coordinate system WGS 1984 UTM fuseau 35 Sud, but my area calculations are still displayed in ...
3
votes
2answers
283 views

How to select polygon features that have their centers outside of another polygon feature class

Since I only have Incorporated area feature class, how can I select census blocks that are in unincorporated area? Or not within any incorporated areas? Thank you. John
3
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1answer
2k views

How do I rotate the polygon about an anchor point using python script?

I know there would be no tool in arcpy module as such but mignt have in third party modules. I however tried taking the vertices of the polygon and moving using the below formula. but did not get the ...