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.

learn more… | top users | synonyms

0
votes
1answer
6k views

How to create polygon with DBGeography Class in Csharp

I want to create a polygon with csharp 4.5 via DBGeometry class. I found example on csharp to create a point via System.Data.Spatial namespace. (Requires Reference System.Data.Entity) This code is ...
2
votes
1answer
207 views

Union of polygons doesn't work 100 % correctly

I'm using the function gUnaryUnion to merge polygons in R. In one particuliar case this doesn't work correctly - some of the old polygon contours are still visible: Can anybody help ?
18
votes
2answers
7k views

How can I find a point inside a polygon in PostGIS?

How can I find a point that is guaranteed to be within a given polygon in PostGIS? I am aware of the ST_Centroid function. However, the centroid is not always within a polygon, see below: ...
7
votes
2answers
3k views

Tips for minimizing shapefile size without compromising geographical detail?

I work for a state government's fisheries service, and lately we've been digitizing a lot of our regulatory boundaries within the state's waters that we'd like to service out on web maps. ...
4
votes
2answers
1k views

How do I find the average distance within a polygon to a point?

For my purposes, I can assume a homogeneous distribution of points within the polygon. What I want to find is the average distance from points within a polygon to a specified point. I don't know where ...
0
votes
0answers
2k views

How to split polygons based on other polygons?

In ArcGIS, I have a layer of polygons (created from the Service Area function) and want to split each one of those based on another polygon layer (the boroughs of London). The purpose is that I want ...
3
votes
2answers
387 views

Detecting ring direction of a polygon using ArcPy

I am using ArcPy in ArcGIS 10.1 to process some geometry using the arcpy.da data access module. However I have run into a problem with complex Polygons that contain inner rings/holes. From the ...
1
vote
0answers
726 views

How to Smooth Polygons after converting DEM using Raster to Polygon?

I have a DEM SRTM that I classify using Spatial Analyst Tools > Reclass > Reclassify. The result is box shaped so I go to Layer Properties > Display and choose cubic convolution. The result is ...
4
votes
1answer
2k views

combine raster and polygon values in R

My question is similar to this one Get Raster Values from a Polygon Overlay in Opensource GIS Solutions but I think I need another step. I have a polygon layer of ecoregions which I brought into R ...
-1
votes
2answers
703 views

Retrieve common paths of polylines ArcObjects

I have a polygon featureClass and a polyline featureClass. I now want to handle all geometries within the latter that are contained in the boundaries of polygon features, that means they shell simply ...
1
vote
1answer
151 views

Move shared vertices together

I should move some vertices of a polygon to fix the boundaries of a country, how can I do it while keeping the adjacent polygons still connected? Is there a way to anchor permanently overlapped ...
2
votes
1answer
2k views

How to find the intersection point of polygon geometry and multilinestring geometry in postgis

I have a polygon geometry and multilinestring geometry. How do i find the intersection of both these geometries. Both the geometries are in same reference system. Does st_intersection gives me the ...
2
votes
1answer
916 views

Distance of points in polygon to nearest polygon edge

I have a polygon shapefile with about a dozen polygons (Area.shp). I have an equation that calculates a value for points (or small areas) as a function of distance to the edge of these polygons. I ...
1
vote
0answers
69 views

How to measure area of polygons generated from gps data in qgis? [duplicate]

Somebody classified my question as a duplicate. But applying the answer doesn't work for me. Here is what I did: - I made sure that my layer is in a projected coordinate system (UTM30N, WGS84) - I ...
0
votes
0answers
149 views

How to create sector figure in ArcObject?

How to create sector in ArcObject 10.1? Now I draw one point, two lines, two arks. But I think it is not good. It is differents objects. I need one object. Well. Now I drawing: IElementCollection ...
1
vote
0answers
285 views

Divide polygon evenly based on lines and intersection points

I have this purple polygon illustrated in the figure below. I would like to split the polygon so that each line segment (green) split the polygon evenly with the surrounding line segments. A line ...
0
votes
0answers
83 views

Unwanted lines when cutting & merging polygons

I am using QGIS version 1.8.0. Sometimes when I cut or merge polygons I get unwanted lines left in them. On zooming in to them they do not appear to be slivers. Is there a way of getting rid of these ...
0
votes
1answer
217 views

QGIS create point data attribute as the name of the polygon it falls in

I'm working in QGIS with a point data set overlaying a farm with 140 fields. While I can analyse the points from each field individually, I would rather use an awk script to calculate statistics I ...
6
votes
1answer
2k views

Identify polygon overlaps within single shapefile

Using either QGIS (1.9) or ArcInfo (9.3.1) I'm trying to identify unique overlaps of prehistoric building footprints from an archaeological site recorded within a single polygon shapefile. While the ...
0
votes
1answer
83 views

How can I know the number of polygons in a selected area in QGIS

How can I know the number of polygons in a selected area in QGIS? Can I use the Select features tool? How can I use? Thank you
4
votes
1answer
2k views

How to add CSV data with no coordinates to a polygon layer in QGIS?

I would like to add attributes from an spss database (around 300 cases) to a polygon layer in QGIS. Both datasets have a column with unique IDs. I exported the spss data to a CSV file which does not ...
0
votes
1answer
106 views

Can this compilation and display of species frequency data be improved? QGIS 1.8.0

As a newbie on QGIS, I would like to find out if the way I put a species frequency map together could be improved upon. I had to map the presence or absence of 7 plant species surveyed in 30 2m x 2m ...
1
vote
4answers
201 views

How can I calculate different polygons by different attributes?

I'm doing my master thesis and want to calculate different polygons (in QGIS 1.8 for Mac) in four different columns which I defined by different attributes. i.e. some of the attributes in the first ...
0
votes
0answers
99 views

Tiles cover Polygon on zoom and move

i'm using OpenLayers.Geometry.Polygon.createRegularPolygon to generate some nice circles. After i draw them to the Map i'm Moving them and after some while they where hiding by some tiles. The circle ...
0
votes
1answer
388 views

How to find and quantify duplicate vertices on a polygon/polyline in ArcGIS 10.0

I need to clean up topological errors in various shapefiles and databases. I did read that the Repair Geometry tool could clean duplicate vertices but how can I know the number of errors before and ...
5
votes
4answers
892 views

How to computational efficiently check if there are any overlapping polygons in a group of polygons?

I need to do some processing with groups of polygons. If any of the polygons in the group overlaps other polygon the result is unpredictable and don't throw any error. So, I need to detect if there is ...
7
votes
2answers
3k views

How do I get that polygon from Javascript ArcGIS API?

I would like to have a user draw a Polygon (or Line) onto a web map with the Javascript ArcGIS API drawing tools. For the life of me I can't figure out how to pull that polygon from the client and get ...
2
votes
1answer
260 views

Tools/Script to reshape automaticaly topologic edges within a given distance in ArcGis 10?

I have a footprint feature class and a land use cluster feature class. I am looking for a method/tool/script that would allow me: to reshape two edges into one (topologically) to decide at which ...
1
vote
2answers
746 views

Where to find the variables of QgsPolygon and QgsPolyline?

now I want to use QgsPolygon (and Qgspolyline,too) class in python I have a example by using QgsPoint but I don't know how to use in QgsPolygon following is my Qgspoint example feature = ...
2
votes
3answers
476 views

How to minimize the number of nodes in a polygon?

I'm building a web application that will be transferring polygons from server to client. Initially, the shapefile is coming from an external source that I have no control over. Often, I find polygons ...
2
votes
1answer
1k views

How to perform a cascaded combine from python script in QGIS?

I'm working with a large dataset, and I need to be able to combine up to 400,000 polygons. I have been using the QgsGeometry::combine(QgsGeometry* geometry) function and simply looping over all ...
4
votes
2answers
1k views

How to average values in a point layer with respect to polygon layer in QGIS?

I am new to GIS and have the following problem: I have 2 layers: a point layer with a column that contains numbers (pollution index from specific measurement point) and a polygon layer with different ...
0
votes
1answer
593 views

In DIVA GIS how can I change the polygon co-ordinates of a .shp file?

I am using polygon layers from various sources to create species distribution maps however some of the layers have different polygon coordinates to others, therefore I cannot use them together as ...
0
votes
0answers
519 views

How to do a spatial join if QGIS 1.8 keeps crashing?

I am trying to perform a simple spatial join (adding polygon data to points) in QGIS 1.8: target vector: points join vector: polygons take attributes of first located feature keep all records ...
1
vote
4answers
329 views

Web service to see postgis polygons

Is there any website or web service where I throw a polygon postgis and he show me on the map this polygon. Example: I put this POLYGON((0 0, 1 0, 1 1, 0 1, 0 0)) and the service show me the ...
1
vote
1answer
175 views

How to paste pictures into data frame?

I have a polygon feature class and I want to trace (select with a polygon) a picture that is solely comprised of a couple of interlocking letters. In ArcMap when I would do this I would simply drag ...
1
vote
2answers
2k views

How to convert self intersecting polygon to multipolygon?

Working with the union and polygonize methods in GDAL/OGR, I often end up with self intersecting polygons. The case is one polygon which essentially consists of two polygons: In the above example, ...
1
vote
1answer
195 views

Remove parts of line that fall within a polygon

I have a polygon and two lines. How can I remove the portion of each line that falls within the polygon? # polygon coords <- matrix(c(-1.798123, -1.793072, -1.805767, -1.804129, -1.798123, 55....
13
votes
2answers
3k views

How to speed up the plotting of polygons in R?

I want to plot the country borders of North America over a raster image depicting some variable and then overlay contours on top of the plot using R. I have been successful in doing this using base ...
1
vote
1answer
83 views

For each polygon, return yes/no value if it intersects another layer

I have a polygon grid overlaying several other polygon vectors. I wish to visit each polygon in the grid and ask yes/no if each of these layers fall within the grid cell or not. I can do this easily ...
2
votes
0answers
272 views

Divide polygon layer by point layer in QGIS?

I have two layers - one polygon layer that is a buffer of a road layer, and one point layer that shows certain locations along that road. What I want to do is to divide/split the polygon layer at the ...
0
votes
1answer
475 views

Knowing the polygon id and getting the extent [duplicate]

I have a text box where I have the polygon Id like, "id_of_the_polygon_12345". Is it possible to get its extent and zoom onto it? I have figured out how to do it upon clicking on the map. But could ...
3
votes
1answer
615 views

Find polygon that contains all linestring records in PostGIS table

I'm still pretty new to this stuff, so bear with me. In PostGIS how could I find a polygon that would contain all the linestring records in a given table?
8
votes
1answer
652 views

How to rectify polygon shapes in QGIS?

I have some polygon-shapes in qgis-1.7.0 and want to ensure that every polygon is a rectangle. See image below. Is there any way I can do this in QGIS (or any other f/oss)? Or how can I improve my ...
0
votes
2answers
1k views

How to scale/reduce my polygon without changing the central lat & long?

I am writing a VBA code to resize my polygon, I get a input as vector points(Shape file). The code below resizes it as according to my scale factor but my central latitude and longitude are also ...
0
votes
1answer
111 views

Selecting a Polygon based on the location of a point

Currently I have a polygon layer made up of three shapes. All the shapes are listed in the attribute table. One of these three shapes intersects a point. I would like to select just the shape that has ...
0
votes
2answers
148 views

Zooming into a particular polygon

I am getting the polygon id by doing identifyParams.geometry = evt.mapPoint; identifyParams.mapExtent = map.extent; identifyTask.execute(identifyParams, function(result) { var i; var ...
4
votes
2answers
148 views

“GIS” Mapping on Monument - Scaling

I have a Baroque tombstone for which I have to map the damage phenoma. Normally one can use a vector drawing programm but one has always two boundaries between the different polygons. Questions: Is it ...
3
votes
1answer
458 views

Masking/removing polygons from shapefile

I have a shapefile containing the road traffic noise of a city. The shapefile has 5 columns, where 'noise_in' (noise interval) ranging from 1-5 is included. I want to remove/mask the road noise from ...
1
vote
0answers
63 views

Are polygons created in Arcpy built in any order?

My script uses a search cursor to evaluate polyline coordinates and build polygons based on those coordinates. The script works well, but I am curious as to whether anyone knows the order (if there ...