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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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 ...
8
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
277 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
740 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
26k 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
4k 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
718 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
246 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
714 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
327 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 ...
17
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
3k 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
585 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?
21
votes
4answers
7k 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, ...