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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6
votes
1answer
815 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 ...
3
votes
3answers
2k views

How to get count of non-NA raster cells within polygon using R

I've been running into all sorts of issues using ArcGIS ZonalStats and thought R could be a great way. Saying that I'm fairly new to R, but got a coding background. The situation is that I have ...
1
vote
2answers
319 views

Polygon inside polygon invalid in QGIS

Looking at this map data from naturalearth (part of Oman & UAE to be specific), each country is defined as a multipolygon. In this case UAE (in red) contains two polygons and Oman (beige) three. ...
3
votes
2answers
423 views

Postgis 2.0 simplifying multipolygon

I have a data set of national boundaries for the African continent. These are in a multipolygon table in postgis. Each country has multiple entries (rows) such that some of the countries in my table ...
2
votes
2answers
147 views

How to select part of the polygon

I have a shapefile of the country. I need to select only percentage of that polygon for demonstration purposes. As an example, how to select 60% of polygon? I am using ArcGIS 9.3.
1
vote
1answer
146 views

draw multipart polygon with one surrounding border

As you can see on the image below, the waterbody is divided by the border line because it consists of several polygons. I could merge the polygon, but I dont want to change the shapefile. Is there ...
1
vote
2answers
1k views

Select points from a table that exist in a custom polygon

We have a property search site where the user draws a polygon on a map and then the app displays all properties that fall within the polygon. We have properties stored within a Postgres table that ...
1
vote
2answers
117 views

Joining data points to matching polygons

I have polygon data on coral reefs at great barrier reef and separate point data for areas of coral bleaching. I have created a clip that only includes points that exist with in the reef polygons. ...
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 ...
0
votes
1answer
222 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?
4
votes
1answer
258 views

How to map flood areas from a set of points containing surface and height of water?

I am working on the damages made by the typhoon Haiyan. I use QGIS 2.0 with extensions and toolbox, and MapInfo. I have vectors, rasters of the place. I want to map the flood area along the ...
1
vote
0answers
342 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
85 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 ...
0
votes
1answer
94 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 ...
2
votes
1answer
767 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
1k 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 ...
15
votes
6answers
16k views

Performing a reverse clip in ArcMap?

Is there a way to perform a 'reverse' of the clip function in ArcMap, I'm not exactly sure how to explain this so here's a diagram:
1
vote
2answers
110 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
1answer
565 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 ...
3
votes
2answers
393 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 ...
3
votes
1answer
173 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 ...
4
votes
1answer
1k 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 ...
0
votes
2answers
76 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 ...
25
votes
4answers
4k 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 ...
2
votes
0answers
50 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 ...
2
votes
3answers
672 views

Shapefile with overlapping polygons: calculate average values

I have a very big polygon shapefile with hundreds of features, often overlapping each other. Each of these features has a value stored in the attribute table. I simply need to calculate the average ...
2
votes
3answers
777 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
1k 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 ...
1
vote
0answers
122 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 ...
2
votes
2answers
3k 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
1answer
752 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 ...
1
vote
2answers
452 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, ...
1
vote
1answer
904 views

How to extracting raster data to multiple polygons?

I have a reclassified raster dataset (10 classes) and I want to find out the area of each class contained within multiple (hundreds-to-thousands) polygons. I have all the polygons in the same ...
1
vote
1answer
217 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 ...
3
votes
1answer
478 views

Determine when I have crossed state line?

We are currently using the Google Maps API to get route information and total mileage but we would like to determine when we are crossing into a new state. When we return the route information we can ...
0
votes
0answers
153 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 ...
4
votes
2answers
4k 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 ...
1
vote
2answers
128 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 ...
0
votes
2answers
492 views

Problems with Polygon Reshape Feature [closed]

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 polygon. But if I create a new polygon in the same shapefile I can ...
3
votes
4answers
3k 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
0answers
238 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
156 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
711 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 ...
2
votes
4answers
2k 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 ...
2
votes
3answers
156 views

How to highlight polygons within another polygon?

I want to symbolize public buildings in OSM data. For Example: There is a polygon and in column "amenity" it has the value "school". But i don't want to highlight this polygon, but the buildings ...
3
votes
2answers
5k 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 ...
2
votes
1answer
42 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 ...
2
votes
0answers
240 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 ...
0
votes
1answer
188 views

Visualizing information when click in polygon‏ - Spatial join

I am new to cartodb, right now I am trying to do something similar to the cartodb tutorial: Create your first map with CartoDB.js, but with polygons using my own map. For example: I did a spatial ...
2
votes
3answers
481 views

Convert surveyor's calls in excel table to polygon shapefile

Do you know of a way to take surveyor's calls from an excel file (for example: N35-45-15W 60.0 ft, etc) and have them generate polygon shapefiles point by point in GIS? I know you can easily do this ...