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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3
votes
2answers
277 views

Search for Multiple Polygons in ArcMap

Is there a way to do a search for features that occupy more than one polygon in ArcMap? I am working with a Parcel layer, and there are some cases where the parcels will take up multiple polygons ...
2
votes
1answer
1k views

Transform polygon to equivalent circle, QGis

I have a polygon and I'd like to find the radius of an equivalent circle from a particular point within the polygon. The polygon would have a large (infinite) number of points evenly distributed ...
3
votes
4answers
360 views

Creating Polys and Displaying geo points within. ( Where to start? ) [closed]

Hey all, I'm somewhat of a newb when it comes to creating mapping solutions. I've stayed on a pretty high level playing with openlayers and pulling data from various webservices. The first part of ...
4
votes
1answer
3k views

Converting tax map polygons from Shapefile to table of map number and corner coordinates

Fairfax County, Virginia provides a Shapefile here which shows the boundaries of the tax maps as polygons. Each polygon simply consists of four corners, and what I'd like to do is create a table ...
15
votes
6answers
6k 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 ...
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 ...
9
votes
2answers
1k views

PostGIS: split a polygon in a given ratio

Is there a convenient way to split a polygon into n parts, more-or-less equal in size in PostGIS?
3
votes
3answers
2k views

How to select the vertices from a polygon?

I am writing some VBA code to extract vertices from a polygon. I would like to ask, how to select the vertices from a polygon ? Regards Gary
2
votes
2answers
564 views

How to query data from a vector map (shapefile)?

We want to obtain the specific place of the boundaries of a shapefile. We want to be able to get the points of each polygon corresponding to a specific place in order to use these data in an ...
6
votes
0answers
696 views

How to split polygons without ArcView? [closed]

I'm trying to split polygons into equal areas. While fishnet sort of works; the areas I'm trying to split don't touch; they're national parks. Fishnet spans the whole area, not just the polygons in ...
11
votes
6answers
4k 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 ...
9
votes
4answers
7k 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 ...
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 ...
1
vote
0answers
276 views

Export topology tables to txt files using ArcObjects, generating directed graph, and finding intersections

I want to export topology tables to text files: for points: 1 id x y for lines: line id fompoint.x from point.y topoint.x topoint.y for polygons: id line id 1, line id 2... 2 arc ...
4
votes
5answers
2k views

Simplify shapefile parcel layer

I have a very large shapefile with over a million parcels within it. The problem I am having is that the polygons representing each parcel are very jagged. What I am looking for is a simple and fast ...
2
votes
2answers
1k views

how trace polyline between two points?(Esri)

How i can draw a line between two points...e.g.: I have initial point and endpoint and i need trace a line between this points...how i can do that?
4
votes
2answers
691 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 ...
8
votes
4answers
4k 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 ...
10
votes
3answers
5k views

How to merge two 'incompatible' polygon layers in ArcGIS?

I have two layers of polygons with administrative boundaries. Although they come from the same data provider, they seem to have small discrepancies and do not 'fit' each other. How could I merge ...
9
votes
4answers
23k 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

Best way to delete selected mass amounts of old data from a polygon shapefile attribute table?

Dumb problem that for some reason is giving me trouble. I have a polygon shapefile that is loaded with old demographic data in its attribute file, I just received the new data today in xls format. ...
7
votes
1answer
672 views

How to determine the longest line segment within a polygon that passes through its centroid?

A PhD student approached me recently asking how one would determine the longest straight line that passes through the centroid of a polygon, the output being a polyline rather than just a table of ...
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 = ...
0
votes
3answers
244 views

How illustrate cells in attribute table?

Firstly, many thanks to all of you who have been helping me greatly, just can say THANKS. Secondly...I have a new question. I have an attribute table with 2883 rows which are the OA of Leicestershire ...
8
votes
2answers
696 views

Splitting polylines using regions with PostGIS

I was wondering if it is possible to split a polyline on polygon boundaries (regions) in PostGIS, the picture below is of what we have at the moment and showing where I need the polylines split: ...
3
votes
2answers
321 views

How to attribute lines with Ids of touching polygons?

I have two shapefiles: one contains streets of a city and one contains blocks (i.e. polygons bounded by the streets). I would like to have the streets attributed with the id of the left and right ...
16
votes
2answers
5k 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
7answers
2k views

Intersection algorithm that correctly handles the 180° meridian and poles?

Is there a well known intersection algorithm that correctly handles 180 meridian and poles? For example, let's say we have a list of latitude and longitude values that represent Antarctica. Let's ...
3
votes
1answer
580 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?
19
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, ...