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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10 views

Proper way to get the radius

I am using GMaps.Net and in the mouse events I can get the lat/lngs. On the mouseDown I get the center point. On the mouseUp I get the lat/lng for what will be the radius measurement. Currently I am ...
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0answers
14 views

Getting the max value from where polygons intersect in MapInfo

I am trying to do an intersect query on two polygon layers in MapInfo. One is a buildings layer and the other are 2d mesh triangles. I want to get the max depth from any of the triangles that ...
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1answer
15 views

Not all polygons removed when cutting from vector layer in QGIS

I have created ten polygons representing lakes on a vector layer, and I am trying to cut them from an imported and re-projected vector layer of administrative districts. When I use the 'Cut with ...
5
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1answer
48 views

Clipping features depending upon percent coverage by other features

I have a shapefile composed of several thousand square polygons of equal size, arranged in a grid. I have another shapefile with a few dozen circles. The squares are about 1/10th the size of the ...
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1answer
25 views

gDistance to determine closest point to polygon: does changing projection change results qualitatively?

I'm using gDistance from the rgeos package for R to find the nearest point to a polygon. The projection of both points and the polygon is +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 ...
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0answers
21 views

Points nearest to polygon: nearest to edge of polygon or centroid?

When using ArcGIS and performing a Spatial Join of points to polygons, there is an option to choose the closest point. Is the point that is chosen closest to the edge of the polygon or to the centroid ...
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0answers
14 views

Aggregate polygons based upon adjacency to an acreage threshold

I work as a forester. I have a feature class of approximately 750 polygons that range in size from a few acres to more than 250 acres. I would like to combine these polygons based upon their proximity ...
3
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2answers
145 views

Extract polygon points

I have a map in .shp format with buildings. I'd like extract the coordinates of this polygon. E.g. if a house has a polygone of 4 points, i'd like to know the coordinates of those points and how to ...
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1answer
18 views

Extruding a 3D stack of polygons on top of a map, e.g. with KML

I have data for the composition of rock layers in several polygons on earth. I would like to plot a stacked chart of the rock layers, colored based on layer metadata. Here's a mockup, where rock ...
3
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3answers
70 views

ArcGIS - possible to set the drawing order of polygon features [duplicate]

I have a table with polygons that I wish to display in a map. I would like the smaller polygons to appear on top of larger polygons. Is there a way to set the drawing order such that the larger ...
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0answers
12 views

What is the best way to store GML polygons in MySQL?

I have large .GML files with polygons of regions around the country, some are a single polygon, some are multiPolygon. What is the best way to store this in MySQL? I was assuming that I would ...
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29 views

different results for area calculations [on hold]

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
23 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
16 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
38 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
63 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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0answers
16 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
35 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
27 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
29 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
votes
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
45 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
38 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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0answers
21 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
39 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
113 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
42 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
120 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
votes
1answer
48 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 ...
1
vote
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 ...
0
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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
55 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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0answers
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" ...
1
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0answers
44 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 ...
1
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0answers
30 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 ...
1
vote
1answer
16 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) ...
1
vote
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
vote
1answer
65 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
votes
1answer
18 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 ...
0
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0answers
25 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
votes
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
votes
2answers
96 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). ...
1
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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 ...
0
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0answers
43 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, ...
0
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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
40 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, ...