Process of creating geometric polygon features.

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2
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1answer
177 views

How to make new polygon/feature from point which is NOT centroid?

I've spent all morning searching help sites and digging through the FAQs and worksheets but have failed miserably. I am an ArcGIS novice so I hope this is not too much of a "newbie" question but I'm ...
1
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0answers
126 views

Problems combining (union) Multipolygons in geodjango

I'm using geodjango and postgis (1.x), What is the best way to combine (union) a list of multipolygons. in what i assume is rather inefficient i'm looping trough like this combined = multipolygon ...
3
votes
0answers
185 views

building larger polygons from smaller ones *without* a common id in PostGIS

I am looking for a means, using PostGIS, of reconstituting a set of polygons from tens of thousands of smaller polygon 'pieces'. This is a simplified example, with the pieces shaded: Unfortunately ...
8
votes
3answers
592 views

How to apply the four colors theorem in a polygon map in ArcGIS/ArcToolBox automatcally?

I need to apply the four colors theorem in a polygonal shape in a way that I do not need to choose manually each color to put in each region. I wish to knows if there is any extension, plug-in, script ...
4
votes
2answers
358 views

How to create a smallest quadrilateral concave polygon around GPS points?

I have this GPS track in a metric grid (Symbology by elevation, if anyone wonders): I need to define it's general area - for registrations and permits, with just 4 points. Therefore, I assume that ...
2
votes
1answer
844 views

how to connect points to create a polygon boundary in QGIS

I have 31 points in a shapefile, which delimit a field (it's an irregular shape). I want to connect those points so they create the boundary of a polygon. Does anybody know a kind of "connect the ...
2
votes
1answer
277 views

Tearing in ggmap (R) after using spTransform and random point generation using splancs

I am using R and the package ggmap to try and generate some random points within the city limits of Chapel Hill, NC. I have downloaded the shapefile for the town of Chapel Hill from the Orange County ...
2
votes
1answer
453 views

Create a shapefile from geometry

Please excuse my lingo, I am still learning some aspects of geo spatial and arcpy. I have a python script that takes a shapefile. The shapefile consists of a polyline. I have traversed the polyline, ...
1
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4answers
489 views

How to create internal polygon without overlap on QGIS1.8.0

I would like to create new polygon inside the existing polygon. It does not means donuts polygon. I would like to have two polygon without overlapping. I can create if I don't check "Avoid ...
7
votes
1answer
684 views

Polygon creation (Clockwise rotation or not)

According to "ESRI Shapefile Technical Description An ESRI White Paper—July 1998", Vertices for a single, ringed polygon are, therefore,always in clockwise order. Otherwise,"Dirty" polygons occur when ...
1
vote
1answer
262 views

Displaying only points within a polygon I created in QGIS?

Thank you in advance for any advice you might give me. I am new to qgis and believe what I'm asking is probably fairly basic. I am trying to map policing activity in NYC for two areas: one area in the ...
7
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3answers
2k views

Extract Overlapping Polygon Data to Points

I have a polygon data set of corn yield collected by a combine. However, as the combine drove through the field, there was slight overlap between passes, leading to overlapping polygons within the ...
5
votes
1answer
305 views

Simplifying polygons made from binary rasters

I'm using MaxEnt to produce a species presence / absence raster layer. It works fine but I have to choose a cut off point for what constitutes presence or absence. As a result I end up with a lot of ...
5
votes
2answers
1k views

Why does this simple Python OGR code create an empty polygon?

Please excuse my ignorance...I am new to Python OGR. I am trying to create a simple square polygon and fail...this produces an empty polygon. Where did I go wrong? from osgeo import ogr driver = ...
2
votes
1answer
930 views

How to draw a polygon with preset length in OpenLayers?

For a project I am working on, I need to be able to put a polygon on a map using OpenLayers, based on a variable point that can be set by a user. The polygon is an isosceles triangle of which two legs ...
2
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2answers
1k views

Problem creating polygon features using ArcObjects / ArcGIS 10

I need to create a grid of polygons. Each polygon is rectangle, thus has 4 corners (vertices). When I create polygon features using ArcObjects they seem to have wrong geometry, which results in wrong ...
0
votes
1answer
114 views

Creating rectangle over a buffer circle with specified angles/rotation?

I have a layer that is a circle buffer around a point. What I want to do is create a rectangle around the circle, but have every rectangle be perfectly lined up N/S (0degrees of angle/rotation). I ...
7
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6answers
2k views

How to split a polygon into quadrants?

I have a Alberta province (Canada) section polygon shapefile in GCS_NAD83 with 255,000 polygons. I like to split each section into 4 equal quadrants (NW, NE, SW, SE) The Alberta province has ...
2
votes
1answer
1k views

Create new polygon layers from postcodes latitude & longitude

First at all, I want to say that I am geocoding enthusiastic but have no formal background on GIS. I'll do my best to use the right wording and make myself clear what I am striving for. Also the only ...
1
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1answer
3k views

Build Polygons from Polylines

I have to build the polygons from some polylines it is an area like a main land(with some boundaries) and some islands around it,islands are building polygons and main land is missing,when i have ...
2
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0answers
260 views

Right click editing menu disabled arcgis 10.0

Editing Polygon feature in FGDB, Create Features, Click Rectangle (in Construction tools), right click, unable to select any options (Absolute X, Y / Direction / Length) from popup menu. Help? Havn't ...
4
votes
1answer
932 views

How to programatically populate a shapefile field with polygon areas in OGR?

I'm trying to programatically populate a shp field with polygon areas: import sys import ogr ds = ogr.Open( 'tttttttttt.shp', update = 1 ) if ds is None: print "Open failed./n" sys.exit( 1 ...
0
votes
1answer
334 views

Polygonizer plugin halts in Windows

I've had some success and some problems using the Polygonizer plugin in the past. I'm using Polygonizer 2.1 in QGIS 1.8 on Windows 7. I'm aware there are sometimes problems using Polygonizer in ...
4
votes
2answers
1k views

How to draw polygons in QGIS perfectly aligned

I would like to draw polygons for an indoor map test and would like to draw perfect rectangles (horiz. and vertical edges). How to set QGIS options on polygon edit /draw to do that ? thank you for ...
3
votes
3answers
1k views

How to digitize polygons from georeferenced raster file

I used QGIS to georeference a raster file of a custom US map. The map has features which are not strictly defined by state borders. I would like to digitize the map by creating contiguous borders for ...
5
votes
2answers
149 views

Create polygon from page size

Is there an easy way to create a polygon that matches the data frame in my page layout? I'm trying to set up data driven pages and want to have it key off of polygons that frame the boundaries for ...
5
votes
1answer
607 views

Polar grids in ArcGIS

I am looking automate the creation of a polar grid shapefile (polygon). I am currently creating this in a many-step editing process, starting from a concentric buffer. Here is how I think I should be ...
0
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0answers
442 views

Why is a Shape polygon file not editable?

I received a .shp polygon file. When I choose the edit toggle tool in QGIS the little red X's appear as expected. Then when I try to edit the polygons such as add a polygon all seems to go well, when ...
2
votes
1answer
1k views

How to create a grid constrained within a polygon in QGIS?

In QGIS I have created an irregularly shaped polygon. I can create a grid based on the maximum extents of the polygon via Vector>Research Tools>Vector Grid. However, what if I need the grid to ...
3
votes
2answers
7k views

Create polygon layer from polyline layer

Our systems expect polygon shapefiles, representing a collection of non-intersecting and geometrically valid (multi)polygons. Specifically, farm fields. We often receive our representations of farms ...
2
votes
1answer
2k views

Converting Raster Data to Polygon data

I am trying to convert a raster data to polygon data. Previously I was using the shapefile.py to create point data on individual lat/lon on the raster. But that will create a Huge data and querying it ...
1
vote
1answer
3k views

How to create a circle with specific radius? [duplicate]

Possible Duplicate: Conflicting measurement units with buffer ftools I have a shapefile as input. How could I create a circle with a radius of exactly 500 meters, using QGIS?
3
votes
3answers
5k views

drawing boundaries in google earth

I want to trace administrative borders as a layer in Google Earth. The problem is that although I know how to draw and save a polygon,I don't know how to draw contiguous shapes using the polygon tool. ...
3
votes
2answers
711 views

How to create a polygon based on view extent in QGIS 1.8 ?

I am looking for a very simple thing. I want to create a polygon based on the current view extent of my project. In fact I want to 1) open google satellite layers 2) zoom to my area of interest ...
6
votes
3answers
2k views

Split polygons programatically

I have looked through several other questions and am still having trouble. I have a set of 103 polygons that span my entire map. Each of those polygons is divided into 36 equal sized polygons. Now ...
1
vote
1answer
384 views

Quantum GIS Garmin Maps62 device and GPS utility - making a polygon for random point

I have a Garmin GPSMaps62 unit and GPS utility. I have logged tracks and need to get these to load as polygon layers in Quantum so that I can then ask Q to give me random sample points and upload ...
2
votes
1answer
3k views

clip polygon with the extents of contour polylines

I have a polygon shape that represents the boundary of Fennoscandinavia and a polyline shapefile representing two contour intervals for a trait. I would like to create a new polygon representing the ...
8
votes
1answer
2k views

Postgis - Converting 'geometry_dump' data type to a 'geometry' type

I am working with a dataset of property boundaries that has had ST_Union() run on it, thus all the polygons appear as a multi polygon in one row of a table. I would like to separate these out so I get ...
2
votes
1answer
3k views

Creating polygons from points in Mapinfo

I have a huge number of points(co-ordinates), from which I am required to draw a polygon in Mapinfo. This required polygon is a square of 200m size. All I have now is the left side lower end of the ...
4
votes
2answers
1k views

Cleaning up OpenStreetMap data, building polygons and trying to improve appearance

I'm currently going through my first project with OpenStreetMap data and I'm struggling to see how certain features can be made to look anywhere near as good as in OpenStreetMap.org. I downloaded a ...
1
vote
1answer
1k views

How to create multipart line and polygon with interior ring in ArcGIS Python?

My objective is to swap X,Y coordinates of feature classes using Python and arcgisscripting. Based on help examples, I managed to write script which reads and writes all geometry types. The problem ...
5
votes
6answers
10k views

Points to Polygon

I've millions of points collected for lithology layer. They have used a coding for different types of rocks. I need to create a polygon around the extent of similar points. What is the easiest way to ...
4
votes
2answers
638 views

Extract all pixels of given RGB value and render as MultiPolygons

Given a geotiff image with a colortable in it, what is the easiest way to extract each color as its own "layer or shapefile or multipolygon object"? Specifically, I am looking for a programmatic ...
14
votes
3answers
2k views

Producing building shadows?

How would you generate building shadows from building footprints? I have attribute values for the heights of buildings. So would preferably like to have the shadows' sizes vary based on that. The best ...
1
vote
1answer
2k views

How to create a circular sector in Mapinfo?

I want to build a tool that creates a cell sector from data like that below. The sector diagram should be like the second picture. The first picture shows a Mapinfo tab file with the required fields ...
5
votes
3answers
1k views

How to find line length in QGIS while editing?

I am using QGIS (before, I used ArcView). I would like to know if there is any way during the editing phase of a vector (line or polygon) to know the length of the line (total and partial) that is ...
2
votes
1answer
377 views

insert maximal number of circles into polygons [duplicate]

Possible Duplicate: algorithm to place maximum number of points within constrained area at a minimum spacing I'm trying to fit as many 30ft diameter circles into polygons of certain land ...
5
votes
2answers
398 views

ArcMap Draw Camera Range with ArcPy

i am working on some camera data. I have some points which consist of azimuth, angle, distance, and of course coordinate field attributes. In arcmap I want to draw shapes like this: The shape is ...
2
votes
0answers
169 views

How to add address block on Google Mapmaker?

Is it possible to mark a block of addresses for example B-block, xyz colony, which is a logical block of addresses on Google Mapmaker? If possible, how do I do it? I want to add a polygon feature ...
4
votes
2answers
2k views

ArcGIS 10.0/arcpy: How to create a polygon geometry from inner and outer ring point arrays?

I have two arrays, each containing a closed ring of points, one for an outer ring and the other for an inner ring, the latter running counterclockwise, of course. I am using the arcpy.Polygon() ...