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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5
votes
1answer
782 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
499 views

Polygonize vegetation area from Landsat7 RGB using QGis / Bilko?

I'm trying to extract the areas with vegetation as a polygon-shape from a landsat7-image, 30m resolution, RGB, using QGis 1.8 or Bilko or (hopefully in the near future) ArcGIS. The area is in Northern ...
6
votes
1answer
2k views

Polygon label repeated for each tile

I'm using the standalone GeoWebCache to serv tiles from a remote GeoServer. My problem is that the polygon label is added to each one of the tiles served, instead of only once in the polygon centroid. ...
5
votes
3answers
346 views

How to combine stacked polygons within a shapefile?

The image below shows my shp-file. Every polygon has the same transparent color. So a darker blue means, that several polygons are stacked! How do I cut every polygon with each other so no polygons ...
0
votes
1answer
73 views

How can we split a polygon within another polygon in Qgis? [duplicate]

How can I split the green area as a separate polygon fro the grey one in QGIS?
18
votes
4answers
2k views

What are the benefits of hexagonal sampling polygons?

I am always on the lookout for useful methods to sample or partition study areas (usually in the form of raster datasets) into smaller units. Recently, I read an ESRI blog post about a new tool for ...
1
vote
0answers
141 views

Why might ArcGIS Export to PDF lose polygon?

How can I solve this problem? After exporting my map to pdf (or any other format), the exported map does not show the basic-polygon-layer, but only a blue/turquoise background with line and point ...
0
votes
1answer
64 views

Using attributes of a polygon in one layer to identify polygons in another

So I'm in the process of developing a web application, I am using open source tools so qgis, postgis, play framework for the web app. And I have come across an interesting problem that I'm trying to ...
0
votes
1answer
61 views

problems using the Split Features tool [closed]

i'm using the split features tool to create two polygons from a bigger one. The problem is, when i save the split i have done, half of the polygon disappears. But sometimes, after doing some more ...
3
votes
1answer
362 views

remove land area from marine region polygons

In my pursuit to merge multiple polygons for the purpose of calculating the surface area of marine species distributions, using shapefiles from Marineregions, I am now trying to remove potential land ...
2
votes
1answer
331 views

How to define polygons overlapping each other?

I have a shapefile of landuse in different catchments. I want to calculate the percentage of each landuse category in each catchment using Tabulate Intersection. Before using this tool, I had ...
0
votes
1answer
685 views

How to extract geo data out of a polygon shape file into csv kwt [duplicate]

I have a polygon shape file that contains all the neighborhoods in the Netherlands. My aim is to export the neighborhoods and coordinates to csv file (KWT). Without success I tried (with QGIS) these ...
1
vote
2answers
320 views

unionize intersections of merged polygons

[Updated quesion] I am using the following code to merged polygons from shapefiles for the purpose of calculating the surface area; library(maptools) library(rgdal) library(rgeos) #enter slots, ...
7
votes
1answer
663 views

How to determine the longest line segment within a polygon that passes through its centroid?

A PhD student approached me recently asking how one would determine the longest straight line that passes through the centroid of a polygon, the output being a polyline rather than just a table of ...
1
vote
2answers
73 views

qgis polygon to coordinates

I have the ordnance survey postcode polygons, i can get the centre point on the postcode (Using polygon centroids) and all the corner coordinates (using extract nodes) Does anyone know how to export ...
3
votes
2answers
143 views

UK area boundaries

I'm working on a web project that requires polygons and lat long coordinates for the boundares of towns, citys, countys and postcodes. Does anyone know where i can obtain this data? i know rightmove ...
2
votes
0answers
47 views

how to assign unique attribute value per neighborhood? [duplicate]

I have a feature class of adjacent polygons and I want to assign an integer attribute value to my polygons based on the following rules : a polygon must not have the same attribute value than any of ...
3
votes
1answer
89 views

Is it possible to split a polygon inside another one in QGIS simply?

I can split polygon if I put the points of start and end outside the boundaries. How can I do the same if I have a part that I want to split completely inside a polygon. In Arcgis I can do it if the ...
2
votes
4answers
481 views

Merge large number of polygons using QGIS

I have a series of polygons that are the output of another GIS program - I need to merge the polygons into a single polygon. I have tried a couple of different methods with no luck. I have tried to ...
0
votes
2answers
61 views

Select area which is at least x meters away from other geometries

In my table I have the build-up area from a region as a big number of polygons. urban_area: id | name | geometry(polygon) I was wondering if and how I would be able to find the area within a ...
4
votes
1answer
629 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 ...
3
votes
1answer
252 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 ...
2
votes
1answer
338 views

Creating polygons using offsets from other polygons

Wondering if you I might get some advice on how to best create a polygon within a polygon based on an offset in ArcGIS. I have one layer that is a cadastral layer and another that is a building ...
2
votes
3answers
316 views

How can I change map scale in ArcMap, after I'm almost finished digitizing? [closed]

I'm just about to design a map that represents different areas in my immediate living environment. I Unfortunately made a big mistake at the beginning of my project. The current scale is given by ...
2
votes
1answer
3k views

How to combine (join?) two overlapping polygons to determine combined area they cover?

How do I combine (join?) two overlapping polygons to determine the combined area they cover in ArcGIS 10? I am sure the Geoprocessing tools can do it, but just how eludes me.
2
votes
2answers
1k views

Polygon country boundaries in decimal degrees

Using Google Maps, I'd like to create draggable polygons (on the fly) of country boundaries (they don't need to be particularly precise). Something similar to this, but for countries. So I want the ...
1
vote
0answers
103 views

Need to enhance a function for creating quadrants within polygons

I wrote a function that creates arbitrary quadrants within a polygon SELECT (quadrant(20,0.0,90)).* The first parameter is the polygon ID, the second one is the start angle and with the third one ...
1
vote
1answer
422 views

How to improve speed of rendering polygons from Postgis in Leaflet?

I want to improve speed of rendering polygons in my Leaflet map. Polygons are stored in Postgis, and are rendered with select query with bbox. I wonder can I cache somehow those polygons? I read ...
4
votes
1answer
156 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 ...
1
vote
1answer
126 views

Polygons not appearing when creating shapefile based on criteria using GDAL and Python (area calculated properly)

I am looping over the features of a shapefile containing multiple polygons. If certain criteria are met, I want to save the current feature in a new shapefile. I am doing this using GDAL 1.10.0 with ...
0
votes
0answers
104 views

Can I simplify polygons in QGIS by Size?

Just wondering if it's possible in QGIS to simplify polygons based on size? I've done it many times using the tolerance level to reduce the overall size however in this case each polygon cannot be ...
1
vote
2answers
86 views

How to convert small overlaping polygon features to inner ring in QGIS

I have a polygon vector layer with overlapping features (like below) and I would like to convert the features that are fully contained inside the bigger polygons (ie feature 2 and 4 below) into inner ...
4
votes
2answers
964 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 ...
2
votes
3answers
490 views

How to remove vertices or lines within a polygon?

I have transformed a *.dxf-file into a polygon shape-file. In many of the polygons i have lines whicht do not belong there but i can not delete them as i normally delete vertices on polygons by ...
0
votes
1answer
182 views

Problems with Polygon Reshape Feature

I'm new in this forum, and i need some help with my project. I've created a polygon and closed my project, after opening the project again, i can't use the Reshape Feature tool in that specific ...
0
votes
0answers
120 views

Calculating distances between boundaries of polygons with Python

I have two sets of shape-files which have to be worked on within a Python Script. Those two Shape Files might differ from each other (same thematic content, but 2 different epochs). If there occurred ...
3
votes
1answer
135 views

Tornado Data Points: Linking 2 Points in QGIS on the Same Row

So I've got these tornado .csv files that have two latitude & longitude entries with the left-most in the table being the beginning point and the right-most being the ending point of the tornado, ...
3
votes
2answers
239 views

Comparing 2 polygon shapefiles for differences [duplicate]

I have 7 shapefiles, each representing a year, all containing lots of polygons (c. 500,000). My aim is to take any 2 of them and compare how they have changed in terms of size and shape of polygon. (i ...
3
votes
2answers
2k views

Determine if point is within an irregular polygon using Python

I would like to create a mask of a grid where points are evaluated as either 1's or 0's depending on if they lay outside of an irregular (i.e. not rectangular) polygon. I have a set of high-latitude ...
3
votes
1answer
67 views

How to re-ID polygons with sapply instead of for loop

I have a line of code that renames the id's of polygons in a SpatialPolygonsDataFrame by directly manipulating the ID slot of the polygon. I'm a bit slow when it comes to sapply, having used for loops ...
2
votes
0answers
141 views

Joining nearest neighbor small polygons using R

The figure shows a plot of numerous polygons (zoom in) made from a raster file by require(sp) require(raster) pol100 <- rasterToPolygons(r, fun=function(x){x==1}, dissolve=FALSE) There polygon ...
2
votes
1answer
39 views

Automatically chopping lumps off polygons

I have a load of polygons that were originally digitised from CAD. These unfortunately include traingles that were used to sybolise the direction the polygon is facing. As can be seen here: The ...
1
vote
2answers
205 views

How to extract common outline of multiple polygons with code?

I'm not really asking for a chunk of code to do this, but more of an algorithm I can work with myself. For example, this is the state of Maine, obviously, and I have the points of each county ...
2
votes
1answer
559 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.
2
votes
1answer
631 views

PostGIS: Calculate the length of just the portion of linestring that intersect with a polygon

I want to calculate the portion of the linestring that lies within the limits of a polygon. Better with an image What is the length of the portion of linestring within Province A? and within ...
2
votes
1answer
757 views

How to get polygons from PostGIS table to PHP array best?

Currently I fetch polygons from a database table using ST_AsText(). The results are in text format, like the following. POLYGON((84 104,212 48,321 122,243 179,275 238,131 240,84 104)) I am not ...
3
votes
2answers
6k views

Cannot get areas for polygon layers in ArcMap 10

For an ArcGIS project opened in ArcMap 10, we have added polygon layers representing different geographical features. After all the polygons were created, we opened the attribute tables for those ...
1
vote
1answer
395 views

Aggregate points with same values to polygons

I have a shapefile with 2M measurement points (each measurement point has a resolution of a 1/10). How can I aggregate points around each other if and create polygons out of it? They do not have to ...
1
vote
1answer
976 views

How to export polygon coordinates?

How can I export each polygon-vertice's coordinate (every point coordinate of every polygon) of a polygon Geodatabase-feature class to an ascii text file (csv or txt)? I don't want to convert it to a ...
0
votes
1answer
106 views

How to automate creating box (rectangular) polygons in ArcGIS for Desktop?

Can anyone suggest a way to automate creating rectangle shaped polygons in ArcMap? If I had many 30m x 60m rectangles to digitize and I just want to click a starting corner coordinate on screen, ...