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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0answers
64 views

Avoid rounding of coordinates in pyQgis

If I get the coordinates of a polygon in qgis by x = geom.asPolygon() It rounds off the coordinate from i.e. -27,200,334.86 to -2.72003e+07 How can I avoid that?
1
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0answers
116 views

Is segment of polyline contained in polygon

I am pretty new to arcpy and am slowly learning all its functions. I have a scenario where I am traversing a polyline. I get a start point and an end point on the polyline and form a segment with ...
9
votes
4answers
8k views

using shapely: translating between Polygons and MultiPolygons

[EDIT: the solution to this was simply to use OGR to read shapefiles. See geographika's example.] In an ESRI shapefile, there is no distinction between Polygons and MultiPolygons. Furthermore, there ...
16
votes
2answers
2k views

Creating Thiessen (Voronoi) polygons using lines (rather than points) as the input features?

I have a set of line features inside a particular polygonal boundary. For each line, I'd like to generate a polygon inside which every possible point is closer to the given line than to any other line ...
5
votes
2answers
525 views

Need an Algorithm to Determining Polygon Borders

I'm currently writing a program in Java and I'm dealing with polygon objects. I want to create a different color border between touching objects depending on their class (i.e. land, ocean, etc). I ...
1
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3answers
4k views

How to auto fill or delete sliver polygons without losing precision?

I am developing some boundaries in which precision holds the key value. Using ArcGIS 9.3 I am converting lines to polygons using the "feature to polygon" tool. The lines are accurate but I find ...
12
votes
2answers
7k views

How to check Topology in QGIS?

I have two Shapefiles with Polygons ( City and Forerst) Is there a Plugin who is able check the topology (QGIS)? Like "Knots do not overlap" or something like that? I dont want that they overlap. ...
4
votes
5answers
1k views

Python loop Polygon to raster not working

I want to convert a large number of different shp polygons to raster in ArcGIS 10.1, using an existing field column "class" for the new raster classes. I am not very fluent in python but I thought ...
3
votes
1answer
1k views

arcpy points in polygon check

I have a list of points and a list of polygons both in a separate shape files. I am trying to write a ArcPy script to loop through the points, and then the polygons respectively and tell me when a ...
4
votes
4answers
3k views

Remove Polygon Islands

I'm really stumped with the problem. I have a polygon layer with no intersects or holes and I need to remove some 'islands', as defined by attributes of a certain size within the layer. It's a hard ...
3
votes
2answers
2k views

How to create a multipart polygon?

I have two polygons that consist of two separate polygons/lines in QGIS). How can I make this into a multipart polygon, which consists of 1 line in QGIS?
9
votes
1answer
776 views

Compare spatial cluster/agglomeration patterns for polygon data

I have agricultural data in form of polygons which I would like to test for spatial clusterings/spatial agglomerations. All in all I have about 40 variables which I can aggregate and standardize in ...
11
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3answers
5k views

How to merge two Polygons in OpenLayers?

I have two polygons. polygon1 = new OpenLayers.Feature.Vector(new OpenLayers.Geometry.Polygon([linearRing1])) polygon2 = new OpenLayers.Feature.Vector(new OpenLayers.Geometry.Polygon([linearRing2])) ...
4
votes
1answer
8k views

How do i calculate line segment lengths within a polygon?

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 ...
0
votes
1answer
1k views

Geojson multipolygon doesn't work with Leaflet bindPopup?

I have polygon and multipolygon data in Geojson format and when I try to bind popup for polygon, it works perfectly, and when I try to bind it for multipolygon, it doesn't work. Is that some Leaflet ...
1
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0answers
32 views

Suggestions for vector format for polygons

I am using two polygon tables in postgis (A and B ). I need to make a vector file that incorporates information of the overlapped polygons B intersecting each polygon on (A). I can make a single ...
1
vote
0answers
70 views

When digitizing, objects are not saved well

I've some problems with digitizing. If I draw a line or a polygon, the line or polygon is saved in the attribute list, but not visible and its location is not saved either (when I zoom to the object ...
0
votes
1answer
5k views

Calculate maximum and minimum elevation for a polygon layer from a DEM [duplicate]

I have a polygon layer and would like to know the min and max elevation within each polygon. My elevation layer is a digital elevation model. I'm not quite sure how to extract that information. I am ...
0
votes
0answers
223 views

Where can I get polygons for the Municipalities of Puerto Rico?

I'd like to find GeoJSON files to draw the polygons of municipalities of Puerto Rico. It might be nice get the Nokia Map (or any reasonable publicly available map) of the same regions and overlay ...
3
votes
1answer
2k views

Merging multipolygon data into a polygon

I have a MultiPolygon representation of some shapes in POSTGIS, I am trying to convert them to Polygon data. I tried, st_geometryn(r.geom, 1) but that didnt work because the way polygons are ...
3
votes
1answer
3k views

find polygon corner coordinates

I am trying to get the coordinates of each node of the polygon I create. I would like the attribute table to display the name of the polygon (ex. address) and then the coordinates of the nodes (ex. ...
6
votes
1answer
452 views

Efficiently identifying overlapping polygons with Python

I'm parsing the NOAA severe weather alert feed and using it as a datasource for a weather alerting system. In the feed, I occasionally find a polygon entry for an alert. Unfortunately, counties that ...
1
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0answers
56 views

Add regular points to each polygon in QGIS [duplicate]

Possible Duplicate: assign and move centroids to their polygons I'm trying to find out a method to define a unique ID based on specific coordinates for each polygon of a shp. The problem is ...
5
votes
1answer
2k views

Create a new vector layer that fills space between other polygons in QGIS

I inherited a clipped (500m radius) land cover map containing vector layers of different land cover categories such as buildings, grass, roads, etc from a colleague. The empty (white) space in ...
6
votes
3answers
2k views

Python OGR: convert a point geometry into polygon

I'm writing a routine for creating the convex hull envelop around shapefiles of islands. I could read the data, extract polygons vertices into a geometry and then compute the convex hull. Now I need ...
6
votes
2answers
370 views

Breaking apart a polygon layer by unique values, creating many new layers

I have a large dataset of habitat information that I need to calculate distances from animal locations to the closest polygon of each habitat type. The way to do this, that I understand, would be to ...
3
votes
0answers
113 views

Create perimeter from given area [closed]

I need to develop a web-based application to manage areas inside a bigger area. I already have the initial perimeter, and it has irregular borders like that: . I will need to tell the app to ...
1
vote
4answers
6k views

Sum of areas in all each polygon layer?

I've got several layers/feature classes in an ArcMap 10 project. Thanks to everyone's help, I'm able to get the areas for the polygons contained within each layer. By opening the attribute tables ...
12
votes
3answers
3k views

Optimizing a nearest neighbor calculation using PostGIS

I'm using PostGIS to calculate the nearest neighbors of polygons. What I want to calculate is the minimum distance from each polygon, to the nearest polygon. Thus far I have got great help from Mike ...
1
vote
0answers
789 views

How to clip the contour map with the polygon using R software?

Hi I am wondering how can I create the contour lines from the discrete x, y and z dataset and then add the shapefile to cut the contour lines by polygon. I want to clip the contour map by the shape ...
4
votes
3answers
584 views

How to subset X number of features from Shape file in QGIS

I'm looking for a means to take a rather large Shape file and split it out into separate, smaller shapefiles based on number of features. So for example, if I have a file with 1 million features, ...
5
votes
2answers
914 views

How to achieve an “inner glow” effect on polygons drawn using the Google Maps v3 javascript API?

Is it possible to produce an "inner glow" effect on polygons drawn using the Google Map v3 javascript API? If not possible using the vanilla Google Maps API, is there a 3rd party tool that can do it? ...
0
votes
3answers
506 views

Calculate 'Rectangle' Coordinates Given 2 Points and width [closed]

I want to create a rectangular polygon using two points as guides. So let's say a journey starts in Egypt and ends in London, my polygon should have 4 points: 10 miles further from London than Egypt ...
3
votes
1answer
433 views

Qgis analysis on polygon

I have a data table mapped and the table also contains further information of interest, beyond the lat/long of the specific data points. I want to be able to draw a polygon and then simply have a ...
2
votes
1answer
104 views

What is the PostGIS function for retrieving buildings by road side?

I want to get information of buildings by the road side only. Assuming that the building table has multi-polygon geometry and the road table has multi-linestring geometry, what would be a pgSQL Query ...
2
votes
1answer
602 views

How to remove a hole from a polygon in OpenLayers?

Is it possible to remove a hole from a polygon by using OpenLayers? How can I do so?
6
votes
1answer
615 views

Generalize large polygon-file

I have a large polygone file with landuse information (6 classes). Its vectorised from a raster classification so the polygons are all angular. Any of my tries to generalize with v.generalize (sneaks, ...
2
votes
1answer
281 views

Obtain normalized raster average per polygon?

I have a raster that contains percentages of total forest killed plus a polygon layer that defines different zones. My goal is to find a good statistical representative that describes the forest ...
9
votes
3answers
1k views

How to sum up values of neighbouring polygons?

I hope that you can help me with the following problem: I have a vector (polygon) layer. I would like to add an attribute to the layer that - for every polygon - sums the values of a specific field of ...
11
votes
3answers
400 views

How to improve drawn shapes in Quantum-GIS?

I have a polygon-shape in qgis-1.7.0 and want to fix overlays and gaps between the edges of adjacent polygons. See image below. Is there any automated way to do this in quantum-gis? Or any other ...
10
votes
1answer
12k views

How to enable “snapping” in Quantum-GIS while drawing polygons?

I tried to draw polygons in qgis-1.7.0 and I somehow can't find or failed to find the "snapping" option. I'm used to ArcGIS-10.0 where you have some snapping options, like placing points of polygons ...
7
votes
2answers
517 views

How do different GIS systems determine a Polygon's interior?

I'm interested in understanding how real-world GIS systems and their data encode Polygons. Specifically, how do they resolve the ambiguity of a Polygon's interior on a sphere? Background: in 2D, ...
7
votes
0answers
394 views

How to write a script to square polygon corners?

I'm looking for a script that will square the corners of polygons that are near 90 degrees but not exactly. Near could be dealt with via a variable, for example within 5 degrees of 90 (85 - 95 ...
11
votes
4answers
2k views

How to colour polygons with a completely transparent fill using MapServer?

Is it possible to fill polygons so that they are completely transparent in MapServer? I want to have a black background that is slightly opaque, and wherever there is a polygon I want that to be ...
0
votes
1answer
822 views

OpenLayers polygon fill not working with GeoJSON file as source

I'm trying to visualise some data in a custom shape on a map, and I'm stuck with styling it. I'm currently using the openlayers framework in combination with a geoJSON file that I generate in code. ...
2
votes
3answers
387 views

How to calculate exact area of a loaded jpg map in to arcmap?

I calculated the polygon area through arcmap.but i'm not sure that the area is not actual,may be scale is not right. so how to calculate the exact area of a jpg image?
3
votes
2answers
1k views

How to filter out multipart polygons and then buffer?

I've written a small script trying to accomplish the task described in the question title. It basically looks like: in_fc = '...' # Some shapefile goes here # Get the fields (column names) of the ...
1
vote
0answers
39 views

area weighted average for overlapping polygons [duplicate]

Possible Duplicate: How to use NASS county level crop data to estimate crop acreage in hydrologic regions? It seems like an easy problem but I don't know how to go about it. I have two ...
5
votes
1answer
2k views

Dissolving specific polygons inside SearchCursor with Python in Arcmap

I have a layer with catchment polygons. For those that are smaller than a certain size, I want to merge with an adjoining polygon (namely the one downstream). In the attribute table I have a GridID, ...
12
votes
5answers
5k views

Get Raster Values from a Polygon Overlay in Opensource GIS Solutions

I have two layers. A polygon-shape-layer with many tiles and a raster-layer containing CORINE 2006 land cover with many categories in a colourmap. I want to obtain for each polygon in the shapelayer a ...