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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18
votes
4answers
6k views

Separate polygons based on intersection using PostGIS

I have a PostGIS table of polygons where some intersect with one another. This is what I'm trying to do: For a given polygon selected by id, give me all of the polygons that intersect. Basically, ...
22
votes
7answers
18k views

Removing small spaces (slivers) between polygons?

I have a set of polygons representing administrative districts. The districts were digitized by hand, and there are small spaces (slivers) between polygons where the polygons should be touching. How ...
20
votes
3answers
2k views

Packing Polygons within polygon

I have a Boolean raster. In the grey areas of the raster I would like to fit a given size polygon within a contiguous extent. Basically, I have an irregular polygon, and i would like to "fit" a ...
6
votes
2answers
7k views

How to calculate polygon areas and perimeters using QGIS?

Using QGIS, if I load a polygon layer and make a new column, how do I fill that column with the: area of each polygon and another column with length of the perimeter of each polygon?
10
votes
2answers
4k 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. ...
8
votes
3answers
2k views

Using polygons to apply unique value to all raster cells within those polygons?

In ArcGIS 9.3, I have a raster file that I would like to "mask" with polygons, giving a single value to all the raster cells that overlap the polygons. How can I do this? Here's a screen shot, ...
5
votes
1answer
694 views

Identify Polygons on raster image

I have OS street view mapping as raster images. Is it possible (without the obvious of tracing each dwelling) to identify all polygons on each tile. To clarify, My ultimate aim is to produce a ...
1
vote
1answer
335 views

How to go with…somewhat complex geological maps in QGIS?

Just a follow-up to this question QGIS: Line to polygon conversion. Not sure do i have to continue there itself... We are currently digitizing a geological map...which has 36 features in total. Some ...
20
votes
3answers
4k views

How can I calculate the average width of a polygon?

I'm interested in examining the average width of a polygon that represents the road surface. I also have the road centerline as a vector (which is sometimes not exactly in the center). In this example ...
10
votes
3answers
15k views

How to convert .shp to .csv including attributes AND geometry?

I have a .shp file with 60k+ entries, all of which are polygons with corresponding attributes (acreage totals, landowner names, tax ID #s, etc.). What I ultimately need is a .csv file with all of ...
3
votes
0answers
187 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 ...
7
votes
4answers
6k views

How do I convert a polygon into a point?

I want to convert polygons into points. I know how it's done in ArcGis and I think this may sound trivial but it's a serious issue :/. I'll appreciate any hints :)
7
votes
6answers
3k views

Lines to Polygons

I have failed to find the "name" of the algorithm that would allow one to convert lines to polygons. Since this issues crosses GIS and the fields of computational geometry and computer science. I am ...
12
votes
5answers
17k views

Extract coordinates of polygon vertices in ArcMap 10?

I've got about a dozen polygons in a feature class loaded in ArcMap 10, all in geographic WGS 1984. How do I easily obtain the coordinates associated with each vertex of each polygon in that feature ...
14
votes
6answers
5k views

Generate points that lie inside polygon

I have polygon feature and want to be able to generate points inside it. I need this for one classification task. Generating random points until one is inside the polygon wouldn't work because it's ...
11
votes
6answers
3k views

How to find the boundary co-ordinates from a given set of co-ordinates

Given a set of coordinates, How do we find the boundary coordinates. <== Figure 1 Given the coordinates in the above set, How can I get the coordinates on the red boundary. Boundary is the polygon ...
4
votes
3answers
1k 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
11
votes
5answers
3k 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 ...
6
votes
4answers
20k views

How to create polygons from lines?

I am trying to create polygons from a line layer of lots and concessions (large blocks of land in rural areas). The lines are mainly grid style as they intersect mostly at right angles. I need to ...
5
votes
2answers
2k views

Converting Longitude and Latitude Coordinates to Square Miles?

I have a set of Long and Lat co-ordinates making up a five point polygon which I have converted in excel using the following formula: ...
3
votes
2answers
638 views

How to Select “Inverse” of intersection of two polygon layers?

I'm wondering if there's a way to intersect two polygon layers, take the intersection, and remove that from one of the polygon layers, making a new layer out of whatever is left over? Basically, the ...
2
votes
1answer
2k 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. ...
1
vote
2answers
85 views

Vertical lines in a polygon shapefile

I am working with a GIS problem using a single input of a polygon shapefile. Consider an irregular polygon. I want to draw vertical lines across the extent of the polygon at equal spacing. How I ...
0
votes
2answers
101 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 ...
11
votes
1answer
3k views

Instantiating spatial polygon without using a shape file in R

So, the usual way we read a shapefile in R is via the maptools package, like this: sfdata <- readShapeSpatial("/path/to/my/shapefile.shp", proj4string=CRS("+proj=longlat")) However, I have a use ...
11
votes
3answers
2k 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 ...
7
votes
3answers
3k views

How to insert a GeoJSON polygon into a PostGIS table?

I need to insert a polygon from GeoJSON to my PostGIS table. This is how the SQL query looks like. INSERT INTO tablename (name, polygon) VALUES ( 'Name', ST_GeomFromGeoJSON ( { ...
7
votes
5answers
2k views

Algorithm to find polygons enclosing points

I'm trying to find an algorithm that can determine the smallest possible polygons to cover a number of points. I know how to get the convex hull around all the points, but say that the points are ...
6
votes
1answer
529 views

Filling a polygon with lines using Postgis

i need to calculate a specific distance in an area. The distance is calculated from parallel lines in a polygon, And i need to find out how many parallel lines (with x meters distance to each other) ...
14
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 ...
9
votes
4answers
21k views

How to split a polygon into multiple equal-width polygons in ArcMap 10?

I am adding parking spaces into a parking lot, and I need them to be exactly the same shape and not overlap each other or have spaces between. In ArcMap 9.3, there was an editing task that allowed you ...
8
votes
4answers
3k views

How to find the minimum edge to edge distance of polygons?

I have a a map of about 3000 polygons in ArcGIS 10. I'm looking to find the distance between each one of them. I know how to do it using the lat and long coordinates of the centroid, but I'm looking ...
5
votes
1answer
1k views

What is the best way to connect spatial data with attributes in Excel table?

I have many attributes which are stored in an Excel table. They refer to USA counties. I need to somehow connect those attributes to polygons in some format (don't know which is the best) and ...
3
votes
1answer
2k views

Calculate polygon area inside extent

We're using ArcMap 10.0 sp5, creating a tool in c# using the ArcObjects sdk. Is there a built in function or simple set of steps that calculates the area of each feature of a polygon layer within a ...
9
votes
2answers
325 views

Creating an “average” polygon

I found this thread in the old ESRI forums with the same type of problem I am facing today. The solution to the problem is explained in little detail and since I am not an expert, I was wondering if ...
6
votes
4answers
3k views

How to remove only donut holes from polygons using ArcGIS Desktop 10.0?

I have a trick for removing the donut holes, which is converting the polygon to line and then creating polygon out of the lines and in the end merging all of them. The drawback of this strategy is ...
1
vote
1answer
800 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 ...
6
votes
1answer
373 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
484 views

How to Create Touching Multi-Part Polygons?

I have a set of parcels as illustrated in the image below. There are currently no multi-part features in dataset. What I would like to do is to merge (not the right word) all of the parcels with same ...
5
votes
1answer
2k views

How can I transform a polygon to a linestring in QGIS?

I have a polygon, imported from a shapefile in QGIS. I would like transform it to a linestring instead so I can save it as a GPX file later. How can I transform a polygon to a linestring in QGIS?
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 ...
4
votes
1answer
1k views

Create overlapping polygons from contour lines

Working in ArcGIS 10, I have a set of contour lines representing density of commercial square footage, and I have a set of points representing local maxima for each peak of the dataset. For each ...
4
votes
2answers
643 views

Including polygons as part of network for ArcGIS Network Analyst?

I am creating a pedestrian walking network of a downtown area. I am digitizing line segments for paths and sidewalks, but I need to incorporate parking lots into my analysis. So far, I have been ...
3
votes
1answer
320 views

remove land area from marine region polygons

In my pursuit to merge multiple polygons for the purpose of calculating the surface area of marine species distributions, using shapefiles from Marineregions, I am now trying to remove potential land ...
3
votes
1answer
390 views

How to make survey lines within polygon?

I am trying to figure out how to make survey lines within a polygon. So first I make a polygon. Now I need to fill this polygon with lines, where I can choose the spacing between the lines, and the ...
3
votes
2answers
267 views

Determine density or cover from a raster layer that has been clipped by a polygon

I am a very new GIS user using ArcMap 10. I have a raster layer of tree canopy that I have clipped so that the layer is in a polygon that is a circle with a 2km radius. I have done this for four ...
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 ...
3
votes
1answer
3k views

How do I rotate the polygon about an anchor point using python script?

I know there would be no tool in arcpy module as such but mignt have in third party modules. I however tried taking the vertices of the polygon and moving using the below formula. but did not get the ...
3
votes
2answers
3k views

Label *beside* polygons in ArcMap 10?

I try to add labels to polygons in ArcMap 10 based on a field in the corresponding attribute table. However, the labels always appear inside the polygon, and I can't find an option that lets me put ...
1
vote
1answer
276 views

How to perform a true GIS clip of polygons layer using a polygon layer in R?

I would like to do a true GIS Clip in R of soils polygons using a series of single boundary polygons, but I cannot find an R function to properly do it. It should work just like the CLIP function in ...