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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11
votes
6answers
1k views

How do I make a heat or Choropleth map that uses polygons in QGis?

I've been playing around with the heatmap plugin for QGIS and I am wondering if it is possible to make heatmap with using a similar plugin/tool that uses polygons as well as points? I would like to ...
2
votes
1answer
815 views

Convert shapefile in NAD27 from meters to decimal degrees to match xy data?

I have a shapefile of a boundary (polygon) that has the following projection: NAD_1927_UTM_Zone_11N Projection: Transverse_Mercator False_Easting: 500000.00000000 False_Northing: ...
1
vote
1answer
2k views

QGIS, how do you break segments of a polygon, ie break 1 polygon into 2 or more?

I have a polygon but would like it to be in broken up to put into different layers. I can't work out how to do this.
2
votes
1answer
340 views

joining a table from zonal statistics as table with a layer, problem with reserved names

I have a raster file (percentage of total forest killed) and a shapefile with polygons (municipalities). I thought as a first step I would like to find out which municipality shows the greatest ...
4
votes
1answer
295 views

Splitting polygons leaves null values

I'm trying to split polygons with overlaping line features, using Split Polygons tool from Topology toolbar. The problem I encounter is that only one from new polygons have old attributes and others ...
4
votes
1answer
1k views

GDAL - creating vector from raster

[SOLVED] Good day! I'm looking at either gdal_contour or gdal_polygonize.py to create a vector layer file from a raster file. I can create the vector file using either method, but it's upside down ...
0
votes
2answers
4k views

How to delete polygon in Openlayers

I would like to delete my polygon in Openlayers after i have drawn it. <html xmlns="http://www.w3.org/1999/xhtml"> <head> <style type="text/css"> html, body, #map { ...
2
votes
2answers
217 views

How can a style be set on a specific polygon using OpenLayers?

Using a polygon id, I want to highlight a polygon, while the mouse is outside of the map area. I can identify the polygon using the following approach: x = 53; for(i=0; ...
5
votes
0answers
177 views

How to rotate polygon to find best fit in Mapnik? [closed]

I have a quite simple problem but somehow I just fail to solve it. There is a polygon and a range xsize and ysize. The x and y size determines the mapnik generated image. The polygon should now be ...
3
votes
2answers
849 views

How to convert polygon layer to txt files?

Is there any way to convert polygons that do not have coordinates in the attribute table to a txt file with coordinates. I will be using the txt file in a different software (not ArcGIS), so I need ...
3
votes
1answer
3k views

How can GeoJson polygons be colored programmatically using OpenLayers?

I'm experimenting with dynamically setting the color values of a geojson polygon. In my geojson file, there is an attribute for each polygon called pop_den. I am trying to update the fillcolor of the ...
0
votes
1answer
168 views

How to add a label of a point to a polygon

i have several polygons with in each polygon a point with a label (number). I want to add the label in the polygon to the attribute-table of the polygon it belongs to.
2
votes
3answers
1k views

Zonal Statistics as table creates output but some are Null

Here is my newest issue: I have temperature as a raster file and different ecoregions of a province as polygons. What I want to do is calculate the mean temperature per ecoregion. I succeeded in ...
6
votes
1answer
1k views

Where can I find a Unesco World Heritage List as boundaries?

I was wondering if anyone knows where to find the UNESCO world heritage list with boundaries? I can extract point data from the json feed for the map on the website http://whc.unesco.org/en/list via ...
3
votes
1answer
843 views

adding polygon to database in openlayers

I want to add a polygon to the database. I used the following code. The problem is that I am to able to save in database. Whatever polygon I draw on map it gets save temporary and as soon as I reload ...
1
vote
2answers
1k views

One Polygon Joining to Database with Many matching records

Using ArcMap 10.1. Is this possible to have one polygon and join to a database/excel with many matching records? I would like to have 1 polygon but match to 100 corresponding records in a table. When ...
6
votes
1answer
404 views

How to draw shapes with highest possible decimal accuracy

I am trying to read input of lat and long to draw the shape based on condition.The input is standard array of lat and long with 15 decimal accuracy. I am realizing - I am loosing some decimal accuracy ...
5
votes
1answer
101 views

How do you edit a stack of polygons simultaneously?

Using ArcMap 10.1. Lets say you have 100 polygons that all are in the exact same shape and in the exact same place. They appear to be one polygon. How would you edit the shape of all 100 at the same ...
2
votes
1answer
235 views

How to join attributes of donut polygon to hole polygon in ArcGIS?

First of all I'm completely new to the realm of GIS and ArcGIS. Basically I need a reliable way to determine a donut hole's containing donut for a few hundred thousand polygons (where the donut holes ...
2
votes
1answer
948 views

Geometryutil, simplify polygon, querytask and query fault error

One of the tools in my app is to draw freehand polygons (counties) to show points (companies) in each county. Everything works great but if the user creates an intersecting polygon then I have a ...
2
votes
1answer
133 views

Compiling a list of units that border each other

I have a shapefile of U.S. counties. I am interested in compiling a list of those that border each other. In particular, I am interested in those that border each other but are in different states. ...
2
votes
2answers
541 views

Creating Long & Lat for Polygons

I have a base map image with micro regions, however in the attribute table there is no information regarding the long & lat. Is there a way I can create a long & lat for each micro region? ...
7
votes
1answer
8k views

How do I change the polygon fill color and border color for SpatialPolygons objects?

I have SpatialPolygons or SpatialPolygonsDataFrames which I'd like to plot. How do I change the color using the three plotting systems in R (base graphics, lattice graphics, and ggplot2)? Example ...
8
votes
5answers
2k views

How to get an ocean shapefile from a very detailed land area shapefile?

I am looking for a possibility to "invert" a shapefile. What I want to do is to convert a shapefile with the continents and islands into a shapefile that has water polygons. The existing ocean ...
4
votes
1answer
543 views

Iterate features on SpatialPolygonsDataFrame in R

I have a SpatialPolygonsDataFrame object. Is there way to use apply on this object rather than using a for loop to iterate features in this object?
3
votes
2answers
2k views

How to edit Shapefile Attributes?

How might I go about exporting a polygon shapefile (e.g. CSV) so that attributes (not geometry) are editable by others, and importing it with the changed attributes (of which there are several columns ...
4
votes
1answer
1k views

How to automate the drawing of polygons (square) around a number of points in QGIS?

In QGIS (or alternatively any other scripting + GIS stack), how can I automate drawing a 100km x 100km square around a number of points, with the point being dead in the center? I'd need to loop ...
6
votes
4answers
325 views

How to avoid holes in polygons from lines?

I am trying to convert a dataset of lines that contains the coast of New Zealand into a big polygon. However using the vector -> geometry tools -> lines to polygon command in Quantum GIS results in a ...
4
votes
1answer
3k views

Arcgis 10: Point layer, polygon line layer, draw points to the nearest polygon point or other nearest line?

I have been using arcGIS for a while now but I often get frustrated with it :( I have version 10.0 arcGIS and I'm have two layers 1) Point data (building locations) 2) a polygon shape file (outline ...
5
votes
1answer
934 views

Export selected raster cells to polygon

I have selected certain values in a raster (roughly 1000 cells), and would like to export them to be able to create a polygon. Converting it to points first then to polygons does not work. Can anyone ...
2
votes
2answers
2k views

Assign unique ID to each polygon

I feel like this should be really simple and I am missing something. All I wish to do is assign a unique ID to each polygon since I have multiple identical FID values. In MS excel I would simply type ...
2
votes
1answer
1k views

Identify duplicate polygons to enable removal after reviewing attributes

I wish to label overlapping polygons so that I can manually locate each overlap then review the attributes of each overlapping polygon and decide which suite of attributes to maintain before ...
3
votes
2answers
185 views

Dissolve column based on attribute in another column

I have 3 columns within a polygon layer I'm working with. Column 1 = Landowner, 3 different values Column 2 = Parcel, N different values Column 3 = Management type, 5 different values I would like ...
3
votes
0answers
188 views

How to estimate the average width of a sidewalk? [duplicate]

I have a table with two polygons representing urban block with and without the sidewalk: geomBlock and geomBlockWithSidewalk. On my city we can approximate the polygons of geomBlockWithSidewalk to a ...
1
vote
1answer
293 views

Summarize polygon area using another polygon

I have a shapefile representing public/private lands in Montana. This is a multipart shapefile where I've simplified attributes so that #1==private and #0==public. Next I have a shapefile of ...
3
votes
1answer
201 views

Enter 4 Coordinates and get a Polygon QGIS

Is it possible to enter 4 Coordinates for getting a Polygon. I have to Clip lots of exact rectangles and i was just wondering wether you know a plugin. Thanks a lot danke! Alex
3
votes
2answers
6k views

How can I display this polygon in Google Maps, properly

NOTE: this question is sorta like a follow-on question to this original GIS Question I asked. In that question, the main suggestion was that I was trying to show two polys. Now, I'm asking about a ...
1
vote
3answers
680 views

How to create a generalized polygon layer from a raster?

I have a tiff file where I have extracted vegetation in a height interval from LIDAR. At the moment the picture is kind of blurry with no data cells between vegetated cells. I would like to create a ...
3
votes
1answer
1k views

How do I split polygons that cross the dateline?

I have a dataset of country borders which I obtained from: http://thematicmapping.org/downloads/world_borders.php/ I have that dataset in both shp and SQL, but I'll put out there that I don't feel ...
9
votes
1answer
377 views

Efficient raster sampling of billions of polygons (bounding boxes)

How can a raster be computed efficiently (in Python), given a set consisting of billions of bounding boxes (read sequentially from a file), and given that the raster values for each cell should give ...
5
votes
3answers
2k views

Finding centrelines from polygons?

I was wondering if there is a way to create centre lines from polygons in QGIS? I have a polygon layer, but ideally need the centrelines as a separate file. Thanks, Alan
3
votes
1answer
3k views

Create polygon based on the spatial extent in arcgis

Is there anyway that I can input 1) The Coordinates System (projected is OK) 2) The boundingbox and create a rectangle polygon based on these?
-2
votes
1answer
672 views

Postgis error on select all intersetcs of a polygon [closed]

i can get all polygon on intersects this:-7.9245860488441 -37.122384500713,-7.9245860488441 -37.11904223938,-7.9233955716106 -37.1187601948 SELECT * FROM propriedades WHERE ST_Intersects( ...
14
votes
4answers
2k views

What is the best open-source web mapping solution for handling 3000+ polygons

I have 3000+ polygons which represent watersheds (18 main watersheds). At the first stage all the 18 watershed will show and their list will be placed in the left sidebar. If any user mouse over the ...
2
votes
2answers
808 views

Algorithm for splitting polygons/polylines into multiple sections at 180° E/W

I have code (in C++) that draws various polygons on a map that uses a cylindrical projection (typically Mercator, sometimes Miller Equidistant if you want to be precise). For simple polygons, curves ...
3
votes
1answer
1k views

How can I get my Qgis area calculations in metres rather than degrees? My shapefiles are projected using WGS 1984 UTM fuseau 35 Sud

I am using Qgis 1.7.4 to calculate the area of polygons. My shapefiles have been projected using the coordinate system WGS 1984 UTM fuseau 35 Sud, but my area calculations are still displayed in ...
5
votes
2answers
1k views

Django PolygonField: how to display on map?

Extremely beginner question. I have a GeoDjango model with a MultiPolygonField. How do I retrieve the value of this field and display it as a polygon on a map? class county(models.Model): cd = ...
5
votes
1answer
192 views

How can I increase performance on inserting features with polygon geometry?

I have a problem when inserting features with polygon feature class in FGDB. This is my code: ... initialising some fields (does not affect performance) m_featureBuffer.Shape = ...
3
votes
1answer
477 views

How to make a minimal distance matrix for polygons using QGIS?

I have a set of polygons and I want to find minimal distances between the edge of each pair of them. It's similar task as in this question: How to find the minimum edge to edge distance of polygons? ...
8
votes
3answers
443 views

Find Duplicate Polygons Algorithm

I have a group of polygons. My objective is to find the duplicate polygons from these group of polygons. Using NetTopologySuite(A c# port of JTS), it is possible to compare two geometires and check ...