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.
5
votes
1answer
165 views
algorithm for displaying holes in a polygon by translating it into several hole-less polygons?
I'd like to plot polygons with holes on a framework that doesn't support holes. The approach to me seems to be to translate the single polygon into several ones adding up to the whole polygon, leaving ...
5
votes
1answer
1k views
How to calculate polygon area considering slopes?
I am looking for an accurate algorithm or a service to calculate surface area on earth where points are calculated on the basis of GPS Coordinates.
I am using Google Map Api version 3 and are drawing ...
5
votes
2answers
256 views
How to combine data from overlapping polygons?
Here's what I'm working with:
Shape file of the current 32 Congressional districts for all states
Shape file of the tract boundaries for Texas
A DBF format table of Hispanic counts and proportions ...
5
votes
0answers
78 views
How to find the maximum-area-rectangle inside a convex polygon?
In this post we are looking for algorithms / ideas on how to find the maximum-area-rectangle inside a convex polygon.
In the following figure, numbers are the areas of the fitted rectangles. As shown ...
5
votes
1answer
72 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. ...
5
votes
0answers
122 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 ...
5
votes
0answers
596 views
How to split polygons without ArcView?
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 ...
4
votes
2answers
1k views
How to calculate polygon areas and perimeters?
If I load a polygon layer and make a new column, how do I fill that column with the 1) area of each polygon and another column with 2) the length of the perimeter of each polygon?
4
votes
3answers
2k 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 :)
4
votes
3answers
478 views
How to identify feature vertices that are part of a donut hole in ArcGIS 10?
I´m exporting the coordinates of polygon vertices to a CSV-File using the "Feature Vertices to Points" and then the "Export feature attributes to ASCII"-tools.
Some of these polygons have holes ...
4
votes
5answers
13k views
How to connect points with a polyline in ArcMap 10?
I have a layer containing a few hundred points representing a survey track. The points are laid out in chronological order in the corresponding attribute table.
How can I have ArcMap 10 automatically ...
4
votes
3answers
213 views
Convert multiple lines into single line
I've no idea if this is basic or what but I have this data that contains multiple lines (forming a polygon shape). I want to convert those lines (multiple - each with a start and end point) to a ...
4
votes
5answers
277 views
Python loop Polygon to raster not working
I want to convert a large number of different shp polygons to raster in ArcGIS 10.1, using an existing field column "class" for the new raster classes. I am not very fluent in python but I thought ...
4
votes
3answers
75 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
(
{
...
4
votes
1answer
271 views
Dissolving specific polygons inside SearchCursor with Python in Arcmap
I have a layer with catchment polygons. For those that are smaller than a certain size, I want to merge with an adjoining polygon (namely the one downstream). In the attribute table I have a GridID, ...
4
votes
2answers
876 views
Is there an easier way to edit polygons in ArcMap?
I am updating woodlot polygons in ArcMap 10. Instead of editing individual verticies, is there a way to edit that is more like drawing part of a new shape (say if the woodlot has expanded only on one ...
4
votes
3answers
2k views
Filling in Donut Polygons in ArcGIS
I'm new to GIS, so please forgive my bad usage of terminology.
I have a set of polygons that represent bodies of water.
In the same feature are polygons that are the islands in the body of water. ...
4
votes
1answer
262 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 ...
4
votes
2answers
4k views
Combining adjacent polygons sharing a similar trait into 1 polygon - ArcGIS
I feel like this is a fairly novice question, but unfortunately I can't seem to find the answer (don't think I'm searching using the correct terms).
I have a large dataset of habitat classes which I ...
4
votes
1answer
959 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 ...
4
votes
3answers
83 views
How to subset X number of features from Shape file in QGIS
I'm looking for a means to take a rather large Shape file and split it out into separate, smaller shapefiles based on number of features. So for example, if I have a file with 1 million features, ...
4
votes
3answers
536 views
How to split features?
I would like to split a shapefile in qgis according to how the polygons overlaps. Don't know how to though? See pic for explanation:
4
votes
1answer
463 views
Copy a polygon geometry in Arcpy
This to me sounded very simple so I am probably missing something basic here.
What I need to do is to create a copy of a polygon shapefile to a new shapefile with slightly different attributes.
Where ...
4
votes
3answers
637 views
OpenStreetMap Neighborhood Boundaries
Is it possible to download neighborhood boundaries from OpenStreetMap? I see on maps that they often indicate neighborhood names; is there a way to retrieve their coordinates and boundary polygon ...
4
votes
3answers
636 views
How to Clip a Vector File based on certain Raster Values?
I need to clip a vector file based on certain values of a raster (Slope > 2%). I can´t find a direct way to do it.
Trying to vectorize the raster first didn´t work.
Is there any tool (ArcGIS or ...
4
votes
1answer
548 views
How to select and copy a group of polygons in QGIS?
I'm new to QGIS. I opened a few shapefiles that cover Europe. Now I want to select a smaller area and if possible copy the polygons in this area so I can work with a smaller set. How should I do this ...
4
votes
2answers
401 views
How to include polygons as part of a network for Network Analyst (ArcMap)?
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 ...
4
votes
1answer
253 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 ...
4
votes
1answer
143 views
Extracting donut holes as separate layer in QGIS
Does anyone know how I can extract the holes in a polygon layer as a separate layer in Quantum GIS? An example could be a country with a number of lakes cut out of the polygon - I need the lakes.
I ...
4
votes
1answer
198 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?
4
votes
1answer
419 views
finding the long axis of an irregular polygon
Hi need some help in how to find the long axis of an irregular shaped ellipse using ArcGIS. I have found the centroid but don't know how to determine the longest distance.
4
votes
2answers
1k views
Removing sliver polygons, ArcGIS 10
I unioned 2 layers into 1 layer, and it created sliver polygons.
I used the elimination tool to merge them with neighboring polygons.
As as result, it merges all sliver polygons to only one polygon ...
4
votes
2answers
340 views
Is it possible to generate a vector polygon from a polygon on a raster image?
I have a raster map which I have extracted from a government report providing flood extent return frequencies. I want to 'snatch' these flood extent polygons (i.e. convert to vector) and I was ...
4
votes
3answers
4k views
How can I calculate the center point inside a polygon in ArcGIS 9.3?
I'm using the JavaScript API 1.6 on ArcGIS 9.3. I have a polygon geometry in an ArcGIS map, and I'm trying to find a way to get the point that lies in the exact center of the geometry. What is the ...
4
votes
2answers
618 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 = ...
4
votes
1answer
54 views
Raster to vector with gaps in Landsat ETM
I need to find size of water area from a raster (jpg) using QGIS 1.8.0-Lisboa. The raster is a Landsat image with gaps of data in it.
I used Polygonize, but the output file shows wrong polygon size ...
4
votes
1answer
340 views
Polygon label repeated for each tile
I'm using the standalone GeoWebCache to serv tiles from a remote GeoServer. My problem is that the polygon label is added to each one of the tiles served, instead of only once in the polygon centroid.
...
4
votes
1answer
214 views
Sub-dividing a polygon into smaller polygons
In OpenStreetMap data, some large areas are tagged with a residential=yes tag. Actually within this large polygon there are multiple smaller (rectangular) houses (which are actually not drawn as yet). ...
4
votes
1answer
1k views
can I extract overlap of polygons within the same layer?
I am trying to extract the overlap of polygons that are within the same layer in 10. The layer came from a buffered street centerline and I'm trying to extract and delete the intersections from the ...
4
votes
1answer
2k 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
869 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
1answer
786 views
How to create a polygon from other polygon boundaries?
I want to write an algorithm that creates a polygon inside a hole made by a set of other polygons. It's something like a flood fill and it's like the "boundary" tool in Autocad.
The image shows an ...
4
votes
1answer
277 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 ...
4
votes
1answer
253 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 ...
4
votes
2answers
686 views
Calculate neighborhood statistics for polygons?
I've been searching around for the answer to this (including here) and have yet to find it. I'm interested in finding out how to calculate a 'neighborhood sum' for vector, polygon data. I am aware ...
4
votes
1answer
938 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 ...
4
votes
1answer
1k views
Convert shapefile lines to a polygon in GRASS
I have a shapefile of a map that is the outline of a number of islands. I would like to convert the lines into polygons (ie all islands filled in) using GRASS. I searched on how to do this with GRASS ...
4
votes
0answers
84 views
How to combine stacked polygons within a shapefile?
The image below shows my shp-file. Every polygon has the same transparent color. So a darker blue means, that several polygons are stacked! How do I cut every polygon with each other so no polygons ...
4
votes
1answer
108 views
MongoDB: Search for polygons which have a certain location
Good day :).
I am trying to implement a search feature on MongoDB using Mongoose.js , the short version of which is this:
I tag locations on a map as polygons. and give them names. Then when an user ...
4
votes
0answers
71 views
Reducing Polygons [closed]
I am merging several data sources into one final answer via a fishnet. My problem is I have landcoverage with multiple attributes unioned to a fishnet. Now I want to eliminate the smaller polygons ...
