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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3 views

different results for area calculations

When calculating the area of a (very simple) polygon, I get a slightly different (higher) result using the field calculator than if I use the function "geometry tools > export/add geometry under the ...
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0answers
18 views

Order a list of points to make a polygon with smooth outer border

I have a function that pulls some lat/longs from a Database and then I put those values in a polygon to see it's shape. The problem is they are so random in position and direction from each other that ...
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0answers
14 views

Merging two regions of several into one, to get output SpatialPolygonsDataFrame file

I've been using the large SpatialPolygonsDataFrame file with outdated border of regions. I want to correct boundaries, but also hope to get in the end Polygons with Data Frame again. I used the ...
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0answers
35 views

How to get a “clean” polygon after using dissolve in QGIS?

I'm trying to obtain the boundaries of shapefile, thus to clean the inside as a matter of speaking. While I had expected that dissolve while get me a proper polygon, unfortunately it still has some ...
3
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2answers
44 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 ...
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13 views

Convert polygons to optimized lat long radius

I have a research project where I need to search Instagram and Twitter for geo coded data. The APIs allow lat, long, and radius, but I have shape files with polygon shapes and some long lines (think ...
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1answer
32 views

How to eliminate polygon overlap areas in QGIS?

Is there a way to remove polygon overlaps within the same layer using QGIS, preferably removing the overlap area of the biggest polygon (having the greatest surface)? All of my polygons are in the ...
1
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1answer
26 views

Number of lines within specified distance of thousands of polygons

I have ~5000 polygons in green (districts). I have storms that I am interested in as red lines. Each storm has a unique ID. Looking to add fields to the districts. The fields are 25km, 50km, 100km, ...
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0answers
25 views

GDAL equivalent to ArcGIS Union?

I have a single shapefile full of overlapping polygons. The ArcGIS Union tool will generate individual, non-overlapping polygons with that geometry. Is there a way to do this with GDAL/OGR or another ...
2
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2answers
66 views

Cutting a polygon out of another polygon with python [duplicate]

Licence: ArcEditor Version: ArcMap 10.0 i have some issues to separat my data with python. To illustrate the problem, i have simplifyed the data with figures. I want to cut the blue polygon ...
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0answers
19 views

Need to find polygon info from postgis

After importing shapefile into postgis I got geom data as MultiPoligon Like: ...
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1answer
44 views

Cannot edit polygons in Qgis

I have a google Layer map on top of which I have added a raster layer of Image and then mapped image coordinates from Google layer. I made transparent (75%) image map layer and now mapping and ...
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1answer
35 views

ST_Intersect with ogr2ogr and Spatialite

I am trying to intersect Spatialite datasets with ogr2ogr, the OGR Virtual Format and SQL Syntax. I can't seem to locate whether the error is in my SQL query or my VRT file. Data ...
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19 views

Efficient way of determining polygon intersection with bounding box

I have a set of polygons, and I need to check whether they are intersecting with a given bounding box(rectangle). What I am doing is, I am taking every vertex of polygon and checking whether it's ...
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2answers
38 views

Automating selection and sliver elimination using QGIS

At the moment I do this manually: open a shape file open the attribute table use "select features using an expression" - the expression is "area" < 200 then I use vector/geoprocessing ...
3
votes
2answers
111 views

How to automatically calculate maximum cell values contained within polygons?

I've got a dataset made up of a large range of polygons (about 70 or so) which represent structures. I also have raster layers which detail a flood depth across an area. The floods depth raster has a ...
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2answers
41 views

testing if a Geodesic polygon contains a point c++

I am looking for an algorithm, preferrably in C++, that can take a point (lon,lat) and determine whether that point is inside a geodesic polygon. Is there such an algorithm freely available?
6
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1answer
118 views

PostGIS polygon edge analysis (orientation, edge length)

I am rather new to the world of GIS and especially PostGIS, so please excuse me if the answer seems evident... I would like to do analysis on a number of buildings. One thing I am interested in is ...
2
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1answer
47 views

Extract raster value to polygon

I am trying to extract raster values within multiple polygons. It would be nice if I could choose between say the maximum or an average raster value within the polygon. For example, I have created ...
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1answer
22 views

How to calculate the area of a raster within a polygon which is greater than a specified value?

I'm using QGIS (2.8.1-Wien) and I have a raster layer showing chlorophyll concentrations in the ocean. I have also defined number of regions of the ocean using polygons. What I'd like to calculate for ...
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1answer
39 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?
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0answers
54 views

Digitizing complex archaeological scenarios in various levels

I don't know if this issue has already been answered, but I can't get my head around it. I used to do this in Illustrator, and there it was simply a matter of clicking "bring forward/bring back" etc. ...
3
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1answer
65 views

Using arcpy to find geometry within another feature

In Arcpy, I would like to start with a point and then using its geometry method to find out if it is inside my polygon feature (Urban Areas) deeper than the buffer distance. This is a follow up to ...
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42 views

Visualizing overlapping polygons by occurence

I work in a library providing geospatial services and I have a patron with about 60 surveys with perceived accent regions in Mexico. Individuals drew on maps where they think people speak with ...
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0answers
15 views

Losing polygons when importing shapefile in GRASS

I have a complicated mapinfo .tab file of wildland urban interface zones. They are represented as polygons. I am importing into GRASS using the following command: v.in.ogr -c dsn="C:....path" ...
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0answers
39 views

Convert polygon to raster and give value to null cells

Is there a way to convert polygon features to raster while also populating null cells with a specific value? As in, can I create a raster from a polygon shapefile and have the tool populate all null ...
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0answers
29 views

QGIS - Polygon to Lines Tool Incredibly Slow

I am trying to convert a few polygons to polylines so I can save them as a .GPX file. I'm using QGIS 2.8.1 (Wein) on the Mac. It seems to be hanging. I only have a few small polygons (see ...
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1answer
15 views

How to Convert db.ListProperty(GeoPt) to GeoJSON Polygon

My Python Google App Engine (no tag?) app has a datastore model of an Area of Interest, simplified as import geojson class AreaOfInterest(db.Model): name = db.StringProperty(required=True) ...
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2answers
27 views

add polygon to layer from text file [closed]

I am completely new to Qgis and to gis in general. I have start to work my way through the documentation but have a question that I can not find a answer to. When looking into the documentation ...
1
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1answer
60 views

Extract data from netcdf using a shapefile polygon in python

I need to subset data from a NetCDF using a specific shapefile. The data are sea surface temperature and ocean color at 1/4 degree resolution. I have 4 polygons describing the US. Northeast ...
0
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1answer
17 views

TopologyException error during fortify SpatialPolygonsDataFrame

I tried to reproduce a recent question on spatial data visualization using ggplot2 and received the following error message during fortify(world, region = "ISO3"): Error: TopologyException: Input ...
1
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0answers
32 views

Correcting polygon geometry so edges can be reshaped to match that of subsequent layer in ArcGIS for Desktop?

I have two layers; a polygon layer representing maritime boundaries/economic areas of countries in the world and another polygon layer representing all countries but with a detailed coastline. In the ...
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0answers
23 views

How to properly import georeferenced .dxf hatches/polygons into QGIS?

I have a georeferenced AutoCAD-drawing (some district borders I vectorized with Illustrator from a raster image), saved as a 2004 ASCII .dxf-file. When I import the file in QGIS ("Add Vector Layer"), ...
2
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1answer
69 views

Feature is a point or polygon

Im new to GIS and am just curious if there is an instance where a feature can be a point in one map and a polygon in another map and vice versa?
3
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2answers
90 views

Creating polygons from line segments using PostgreSQL and PostGIS

Is there a PostGIS function that creates polygons from multiple line segments? I want to convert the pictured thirteen lines to four polygons. All lines belong to the table "boundary" (gid, geom). ...
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0answers
24 views

Progress Bar gets stuck converting Lines to Polygons using QGIS?

I'm trying to convert lines to polygon using QGIS 2.8.1. I use Vector > Geometry Tools > Polygons to Lines. I always get the progress bar stuck on 90%, it can't get to 100%. Could someone ...
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0answers
38 views

Grouping Analysis (Clustering) of polygons with streets as borders in ArcGIS?

I have a question about the Grouping Analysis Tool in ArcGIS. Is it possible to use streets as spatial borders for the groups? I want to group a city district autmatically with multiple attributes, ...
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0answers
10 views

How do you snap polygons as you draw in QGIS? [duplicate]

I need to draw a long row of patient rooms for a hospital. I have the following plugins installed in QGIS 2.6: Rectangle Ovals Digitizing CAD Digitize I want to drag a set of polygons that aligns ...
2
votes
0answers
36 views

Different obs. when I extract raster values from polygons in R

I have two raster layers with the same projection, extent and resolution: r1: class : RasterLayer dimensions : 33434, 89431, 2990036054 (nrow, ncol, ncell) resolution : 0.001447053, ...
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0answers
42 views

Matching (joining) two slightly incompatible polygon shapefiles

I have two shapefiles that represent two slightly different zonings of the same area (municipality zoning and transport zones), about 3000 polygons each. Several smaller municipalities may form a ...
1
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0answers
31 views

Sample points based on underlying polygon attributes

I have a point shapefile and I would like to sample those points (just like the "Sample" tool allows points to sample underlying raster) to receive a table with underlying polygon values (interested ...
1
vote
1answer
26 views

Using pyQGIS transform a layer of polygons into a layer of holes inside a bbox

I'm using python in QGIS. I have a layer of polygons (its a result of some earlier dissolving and has no overlapping polygons but some holes and islands in holes etc). I want to build a new layer ...
0
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0answers
24 views

Selecting polygons using another polygon? [duplicate]

Hi, How is the best way or fastest(if there is) of selecting polygons of a different shapefile using a polygon of another shapefile. exercise example: i want select all the light brown polygons ...
1
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0answers
48 views

Why does the transformation bring bad results?

I have this map which has a polygon drawn on it. For the background map I use a WMS via ol.source.TileWMS and the polygon uses a ol.source.Vector object. Normally my view projection is EPSG:31467 but ...
1
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2answers
92 views

Is there any library can perform polygons buffering/ inflating/ merge/ overlap at server side?

I have a set of polygon data express in lat long. I would like to perform some tasks (polygon buffering, inflating etc etc ..) in server side and output the result to client side (client is a web ...
0
votes
1answer
27 views

Python error in polygon to raster conversion

I want to convert polygon to raster. I converted the dbf file ( "cntymam") to table view to make use in the conversion. I am getting a error that the parameters are not called and also with the grid ...
0
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2answers
42 views

How can I find internal overlaps in my polygon feature class ideally via modelbuilder tools?

I have a polygon layer containing "depth curves" for the making of a skin of earth kind of map. I want to check whether or not my feature class contain any overlaps internally between these polygons. ...
1
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1answer
53 views

Select points near polygon in Postgis

I'm trying to make a spatial query, but I think something is wrong with it: I have two tables, places (point) and cities (polygon) When I try to get the points within 500m to one point, there is no ...
2
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0answers
35 views

Redistribution of polygons: supplementing and filling the specific area with polygons with specific size

I'm studying the impact of green wedges (red outline on the figure) on weather parameters in Copenhagen area. What I want to do is check how spatial redistribution of future afforested areas enacted ...
1
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1answer
71 views

draw square openlayers 3

I am starting to convert old code of openlayers 2 to openlayer 3. In the old version you could make polygon shape based of the amount of sides like in the example below: ...