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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2
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1answer
40 views

How can I subtract one (very very large) set of features from another?

I'm trying to subtract a very large set of features (water areas) from another, relatively small set of features (land area). In principle, I should be able to do this in QGIS using Vector > ...
5
votes
1answer
147 views

Adding new nodes in the middle of each líne of a Polygon

I am currently working on a Street Lighting Network. I have two layers in PostGIS ( PostGIS 2.1.3 and PostgreSQL 9.3.5): Manholes (56.000 Polygon) Pipes (Linestring) The manholes are perfect ...
0
votes
1answer
34 views

Convert this CSV to a qgis usable format

I have been given a CSV (which has been converted from a RDF). I want to convert the CSV file to a usable format so that I can display these polygons in QGIS. The original file and some other ...
1
vote
0answers
30 views

Forcing polyline to offset from polygon border

I am currently working on a site with polygons and polylines and am looking for a way to ensure that the polyline does not overlay the site boundary. I am creating a habitat map and do not want the ...
1
vote
1answer
30 views

Do we have a way to change the colors of the polygons directly in JOSM?

Do we have a way to change directly the colors of the polygons in JOSM?
0
votes
1answer
72 views

How can i convert the coordinates (latitude,longitude) to X,Y using postgis

I want know how i can convert the latitude and the longitude coordinates of a rectangle in the Cartesian coordinates, so I can store them in a geometry field using postgis.
2
votes
0answers
45 views

QGIS : How to calculate centroid on polygons with holes

I try to compute the centroid of polygons with holes on qgis. I did not manage to do it directly, I had to make a conversion to convex hulls before extraction. I crashed my pgsql server trying to ...
8
votes
3answers
3k views

r - increase speed of crop, mask, & extract raster by many polygons

I'm extracting the area and percent cover of different land use types from a raster based on several thousand polygon boundaries. I've found that the extract function works much faster if I iterate ...
2
votes
2answers
1k views

Tracing polyline between two points in ArcGIS Desktop?

How i can draw a line between two points...e.g.: I have initial point and endpoint and i need trace a line between this points...how i can do that?
2
votes
1answer
59 views

Polygons between contour lines in QGIS?

I am trying to create polygons between contour polylines within a defined area (for which i have both polygon and polyline shps) but I seem to be thwarted at every turn. Using QGIS 2.14, I am sure it ...
5
votes
4answers
16k 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 ...
0
votes
0answers
21 views

Using the extract function in raster package for R with polygons

I have a shape file that contains some polygons and an unprojected raster. I'd like to extract the cells within the polygons using R, so I use code like this: # Load my polygons MyPoly <- ...
1
vote
2answers
2k views

How to spatially join polygon fields onto a point layer in QGIS?

I have gridded depth points in CSV format that I'm trying to add other map data to, in additional columns. I've tried joining fields, hoping that I could link the Shapefile data to the csv, but when I ...
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 ...
7
votes
3answers
1k views

Is there a way to “invert” Polygons?

I have a Shapefile with Polygon features representing the world's land areas (continents, islands). Is it possible to invert these, and get a geometry that represents the world's oceans and seas? So ...
1
vote
1answer
38 views

How to find the area with most intersection for buffer regions?

Find the area with the most intersection This question relates to previous question asked - How to find the intersection areas of overlapping buffer zones in single shapefile?. I tried to ...
4
votes
1answer
74 views

Altering elevation of specific cells in raster layer of QGIS?

I'm looking to alter the height of some cells within a raster and it's been suggested that I do this by creating a polygon layer and use that as a mask to alter only the heights of cells within the ...
1
vote
1answer
29 views

How do you create a rainbow polygon hover effect in Mapbox?

We're working on a fun website called VicePrice. It's a happy hour website using GIS instead of a list directory to show happy hour info. We've run into a snag and perhaps someone could give us their ...
2
votes
1answer
109 views

How to find the intersection areas of overlapping buffer zones in single shapefile?

Find the intersections of the buffer zones I found an example where they tried finding the intersection of two different shapefiles -Intersect Shapefiles using Shapely. I've tried to adapt my code to ...
0
votes
0answers
49 views

Leaflet self-intersecting polygons display

Is it possible to set colors of the actual intersections of self-intersecting polygons in Leaflet? Example of such self-intersetions can be found on the pic below, the transparent triangles inside of ...
3
votes
1answer
28 views

How to obtain attributes of a point layer that falls within a polygon layer of different CRS

I have created my own vector grid polygons in QGIS 2.12.2. This creates a new layer to my project, but it's projected in a "generated projection". I want to view the attributes of points that fall ...
1
vote
1answer
27 views

Setting final orientation of polygons in CityGML model

I am converting shapefile model of buildings in LoD2 to CityGML. In CityGML really matter about poylgon orientation(Countercloskwise can be seen from outside, Clockwise from inside). I have problem ...
2
votes
1answer
67 views

Using Chaiken Method parameters for smoothing polygon vectors in QGIS [duplicate]

I've been trying to smooth a huge polygon, that is result of a segmentation export. I'd like to know what's the best parameters to use Chaiken Method to get smooth curved boundaries on QGIS 2.14. I ...
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 ...
4
votes
2answers
1k views

What methods exist for geohash of polygon?

GeoHash is an excellent method to code the latitude and longitude of a point into a string. It's concise, due to the use of numbers + letters, and the precision can be tuned adding characters at the ...
0
votes
1answer
59 views

Python Calculate Cumulative Polygon Areas (Basins)

I've been asked to automate the calculation of cumulative polygon areas within a basins shapefile. The calculation will take the area of the upstream basin and add it to the area of the downstream ...
1
vote
2answers
892 views

How to convert features of layer from POLYGON to MULTIPOLYGON?

How can I convert features of a layer from POLYGON to MULTIPOLYGON? I know how to do that using the postgis function ST_Multi but how could I do to same thing for a layer in QGIS?
0
votes
0answers
44 views

How to scale polygon to obtain specific area in javascript?

I have got a source polygon (saved as standard js array). I want to scale it down to obtain new destination polygon in the centre with 1/3 of source area. On the cartesian space i just scaling down ...
1
vote
1answer
32 views

Shapefile with point or polygon

I'm just beginning with SIG and QGIS. I've been given two shapefiles with cities. One shapefile appears like point shapefile in QGIS, the other like polygon shapefile. The problem is that the ...
0
votes
0answers
31 views

Clipping algorithm that can make one layer with no overlapping polygons from N polygons

I am looking for an algorithm description / pseudo code for an algorithm that can take N simple polygons and return a new set of polygons that all have been clipped such that there is no overlap in ...
2
votes
1answer
87 views

Creating shapefile from polygon points for CartoDB?

I have an Excel file that contains polygon coordinates for different areas. The spreadsheet has three columns: latitude, longitude and area name. Each coordinate makes of a part of the boundary of a ...
1
vote
2answers
81 views

problem combining geometries from all features in a layer as one geometry

I am trying to combine all features of a Polygon layer in QGIS in a python plugin, and am running into this error when I try to run the combine method: "AttributeError: 'NoneType' object has no ...
0
votes
0answers
66 views

How to load points in a SQL server polygon table?

I have a spatial table in SQL server which stores both points and polygons geometry and I am using the table to return geoJSON for API calls. I want to load some points to this table with shapetype ...
1
vote
1answer
16 views

Shapefile of South Tyneside borough (north-east England) boundary

I'm looking for a free-to-download shapefile (polygons) of South Tyneside borough. South Tyneside is a metropolitan borough in NE England. Can anyone help?
1
vote
1answer
55 views

Does QGIS have an autocomplete polygon option like the one in ArcGIS?

I am trying to do digitizing in QGIS, but I do not see an option that I have seen in ArcGIS - autocomplete polygon. I would like to make two adjacent polygons topologically correct, and can not find ...
2
votes
1answer
99 views

How to use GIS data with CGAL?

I read a few posts here at GIS.SE that points to useful algorithms in CGAL. I'd like to test algorithms in CGAL such as medial axis transformation/polygon skeleton extraction, but the examples on the ...
0
votes
1answer
198 views

Spatial Join in R

I'm fairly new to using R for spatial work so bear with me. I have found questions similar to this but nothing that answers this question specifically enough for me to implement it. I have point data ...
1
vote
1answer
617 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 ...
2
votes
2answers
149 views

points within a polygon

Since I am a beginner to postgis I am facing problem with finding points within polygons from my table. This is my table structure Column | Type | ...
0
votes
0answers
43 views

NDVI polygon from NDVI raster

I am currently working with NDVI data. I found this format which seems to be preferred by our clients: Our maps are made in ArcGIS, I've tried running classification but classes won't allow me to ...
16
votes
5answers
9k views

How best to fix a non-noded intersection problem in PostGIS?

I'm using a PL/R function and PostGIS to generate voronoi polygons around a set of points. The function that I am using is defined here. When I use this function on a particular dataset I get the ...
3
votes
1answer
43 views

polygon split with predefined area

I am trying to split an irregular polygon into 120 equal area blocks. I also need a buffer around each new block within the polygon. Is this possible in QGIS 2.12.1?
0
votes
0answers
34 views

Comparison of polygon geometry of 2 layers (ArcEditor)

I´m facing the following Issue: I´m trying to find changes between 2 continuous polygon layers. Polygons that need to be compared dont have matching IDs - to explain, I have polygon X and polygon Y ...
0
votes
2answers
67 views

Remove lines from inside a polygon (shapefile) in r

I have this code which prints the Galápagos Islands. But inside the islands, there are lines that I want to get rid off. How is this possible in R? library(rgdal) library(ggplot2) URL <- ...
0
votes
1answer
243 views

Serving one large polygon or many little ones from ArcGIS Server?

I´m designing a geoprocessing service on ArcGIS Server using several nationwide datasets. Currently I´m preparing some of the datasets and I´m wondering if I should dissolve my polygon layers ...
1
vote
0answers
307 views

how to automate changing polygon's shape while keeping its area the same and limiting deviation from orginal centroid? [closed]

I have a polygon that was digitized based upon visually interpreting underlying values of rasters/vectors that represent a natural environment (soil type, surface roughness, slope, elevation, ...
8
votes
3answers
3k views

Order of polygon vertices in general GIS: clockwise or counterclockwise

Two days ago I asked a question about the internal storing order for the vertices of a polygon in ESRI shapefiles. That question was answered (Are polygons stored clockwise or counterclockwise in a ...
1
vote
2answers
986 views

Looking for dissolve algorithm for Javascript

I have three adjacent polygons that together make up a larger shape. I need an algorithm that will dissolve the internal borders leaving only the outside border. An example would be a group of ...
0
votes
0answers
29 views

Feature Layer parameter showing only Polygon Shapefiles

I have created a Python Tool in ArcGIS where most of the paramaters musts be ONLY Polygon Shapefiles. You can also look on my previous question: Filter the Feature Layer parameter in Python Script ...
4
votes
1answer
46 views

Find polygons that does not contain (any) polygons with PostGIS

New to PostGIS, I have a polygon layer of water catchment areas which are formed by the specific monitoring points along the river upstream. For example, on one river, there could be multiple areas, ...