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
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
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
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 ...
3
votes
0answers
49 views
Masking/removing polygons from shapefile
I have a shapefile containing the road traffic noise of a city.
The shapefile has 5 columns, where 'noise_in' (noise interval) ranging from 1-5 is included.
I want to remove/mask the road noise from ...
3
votes
0answers
156 views
Polygonize vegetation area from Landsat7 RGB using QGis / Bilko?
I'm trying to extract the areas with vegetation as a polygon-shape from a landsat7-image, 30m resolution, RGB, using QGis 1.8 or Bilko or (hopefully in the near future) ArcGIS. The area is in Northern ...
3
votes
0answers
98 views
Closest set of points to another set of (predefined) points
I have 10 sets of points which I call templates that I have manually classified from 0 to 10. Each point is a X, Y coordinate in a text file. Each template has 5-8 points.
I have new sets of points ...
3
votes
0answers
74 views
Why doesn't Polygonizer copy the line ids to my polygonized shapefile?
I am trying to convert a line shapefile into a polygon shapefile using Polygonizer plugin, and when my new polygons are created all the cells in my id field are "Null", although I have clicked "copy ...
3
votes
0answers
126 views
Rgeos drops associated values when intersecting polygons
I am trying to intersect two SpatialPolygonsDataFrames and get a SpatialPolygonsDataFrame as the result. Unfortunately, using the gIntersection function from rgeos (which works impressively quickly ...
3
votes
0answers
116 views
Area-weighted rasterising of polygon data
I'm looking for any GIS tool to do detailed rasterising of polygons. I've checked GDAL's gdal_rasterize command (and API), and ArcGIS's Polygon to Raster tool, but they only rasterise 1 attribute per ...
3
votes
0answers
55 views
Passing attributes to neighbouring polygons
I have an ecosystem polygon layer that has been updated using a more recent tree cover layer (to remove cleared areas and also to re-align veg boundaries where growth has occured).
Where the polygons ...
3
votes
0answers
168 views
How to write a script to square polygon corners?
I'm looking for a script that will square the corners of polygons that are near 90 degrees but not exactly. Near could be dealt with via a variable, for example within 5 degrees of 90 (85 - 95 ...
2
votes
0answers
26 views
Clipped raster leaks outside polygons
I am trying to clip a raster (DEM) with a polygon layer in ArcGIS10.1, using Data Management>>Raster>>Clip. Basically the clipped raster has many pixels outside the polygon boundary, mainly for thin ...
2
votes
0answers
72 views
Problems converting polygon to point
I'm trying to convert polygons to points with ArcGIS 10. My polygon layer has 2 attributes that I want to give to my point layer. I'm using the Feature to Point function from the Arctoolbox, but it ...
2
votes
0answers
42 views
Matching points in table to polygons
this is my first post to this forum. I hope to start participating actively.
I have a table with several records (aprox 200.000), each with its own coordinates. And I need to identify the "Polygon" ...
2
votes
0answers
65 views
Cannot reselect polygon after modify
I've got various vector layers on a OL map.
On one layer I have a few draw controls. If I draw a polygon I can select it (the whole pop-up thing works). This also works for all the other features.
...
2
votes
0answers
93 views
How to dissolve polygons that have been split back into their original polygons?
I had a feature class containging about a thousand polygons.After some processing such as intersecting, dissolving, merging, more intersecting, I ended up with a feature class of about 6000 polys. ...
2
votes
0answers
120 views
how to automate changing polygon's shape while keeping its area the same and limiting deviation from orginal centroid?
I have a polygon that was digitized based upon visually interpreting underlying values of rasters/vectors that represent a natural environment (soil type, surface roughness, slope, elevation, ...
2
votes
0answers
337 views
cant find point/polygon intersect using qgis (windows only)
below i describe the method i am using.
i have 2 machines: 1 ubuntu linux, qgis 1.4 - intersection works
2 WIN xp, qgis 1.8 - intersection dows not work
hopefully, someone will ...
2
votes
0answers
433 views
How to calculate the area of a polygon considering the relief?
I work in a fire department and i'm mapping all the fires that occur in my area, creating polygons that represent burnt areas.
my problem is that the values are not accurate... for instance, arcgis ...
2
votes
0answers
63 views
Determine which points fall within a 3D polygon and export this subset to a flat file
I am working in ArcMap 10 and will have a 3D representation of a zone of transmission. I would like to determine which GPS points fall within this polygon and then export this subset out to a flat ...
1
vote
0answers
48 views
Are polygons created in Arcpy built in any order?
My script uses a search cursor to evaluate polyline coordinates and build polygons based on those coordinates. The script works well, but I am curious as to whether anyone knows the order (if there ...
1
vote
0answers
70 views
Line to Polygon via Polygonizer in QGIS
My question is in the same vein as this one.
I'm attempting to convert precipitation lines (Precipitación Media Anual) to a polygon for Mexico in QGIS using the Polygonizer plugin.
After running the ...
1
vote
0answers
60 views
How can I move two layers at once in QGIS?
I'm trying to move two digitized layers, one containing points, the other polygons to a different location at the same time. QGIS doens't seem to allow this. Even if I select both layers and features ...
1
vote
0answers
39 views
graduated pattern polygon fill
I'm sure this question is really really basic but I appeal to you because I hate the idea that I have spent 20 minutes trying to do such a simple thing...
All I want to do is style a polygon layer by ...
1
vote
0answers
39 views
Avoid rounding of coordinates in pyQgis
If I get the coordinates of a polygon in qgis by
x = geom.asPolygon()
It rounds off the coordinate from i.e.
-27,200,334.86
to
-2.72003e+07
How can I avoid that?
1
vote
0answers
54 views
Is segment of polyline contained in polygon
I am pretty new to arcpy and am slowly learning all its functions. I have a scenario where I am traversing a polyline. I get a start point and an end point on the polyline and form a segment with ...
1
vote
0answers
26 views
Suggestions for vector format for polygons
I am using two polygon tables in postgis (A and B ).
I need to make a vector file that incorporates information of the overlapped polygons B intersecting each polygon on (A).
I can make a single ...
1
vote
0answers
50 views
When digitizing, objects are not saved well
I've some problems with digitizing.
If I draw a line or a polygon, the line or polygon is saved in the attribute list, but not visible and its location is not saved either (when I zoom to the object ...
1
vote
0answers
313 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 ...
1
vote
0answers
170 views
How to clip the contour map with the polygon using R software?
Hi I am wondering how can I create the contour lines from the discrete x, y and z dataset and then add the shapefile to cut the contour lines by polygon.
I want to clip the contour map by the shape ...
1
vote
0answers
181 views
How to handle postgresql/postgis geometry type errors in a function?
I have created the following function in PL/SQL to make a polygon from a set of linestrings:
CREATE OR REPLACE FUNCTION _myfunction(
_fid integer,
_rid integer
)
RETURNS VOID AS $$ ...
1
vote
0answers
67 views
Creating responsive interaction with tiled maps
I think I may have two conflicting aims but...
I need to create responsive Choropleth map very similar to http://leafletjs.com/examples/choropleth.html or
...
1
vote
0answers
56 views
footprint polygon from raster data with postgis
how can I create a polygon, containing the actual outlines (aka footprint) of a raster file with postgis?
I just need the outlines of the data containing parts of the raster.
ST_PixelAsPolygon ...
1
vote
0answers
77 views
How to construct a line from points in pyshp?
I am reading a shapefile for a pipeline and what I've noticed is that if I just draw a line from one point to the next (in the order I read them), there will be points where the line terminates, and ...
1
vote
0answers
148 views
When I finish drawing a polygon, it disappears again (although appearing in my attribute table)
I'm working with Quantum GIS at this moment. And as the title says, when I finish drawing a polygon, it disappears again. The new object does appear in my attribute table and in the legend/'filling of ...
1
vote
0answers
49 views
I want to split a worldwide 'road dataset' into multiple grids/blocks-extents, depending on the amount of features resides in that block-extent
I want to split a worldwide 'road dataset' into multiple grids/blocks-extents, depending on the amount of features resides in that block-extent. If the amount of features(inside that block) is still ...
1
vote
0answers
118 views
Polygons of Land Use Change
I am doing a project where I am digitizing a map of Haiti from the 70s. Through R2V I digitized the lines and then I exported it into ArcGIS 10. I am just interested in the land use change, therefore, ...
1
vote
0answers
98 views
identify the fraction of raster cells and listing all the cell values in every polygon
In Arcgis 10 I have a netcdf file that maps the fractions of cropland in the world from 1700 to 2007. I extracted the years that i needed as raster layer format (continous data from 0 to 1) and now, ...
1
vote
0answers
84 views
Getting started with storing LoST and GML searching
I am working on a logging and search database application.
The application will receive event records containing XML LoST values (RFC5222 Location-To-Service-Translation). These records will be ...
1
vote
0answers
237 views
export topology tables to txt files using arcobjects, generating directed graph , 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 ...
0
votes
0answers
12 views
How to obtain a region polygon from Google Places Autocomplete
I am trying to use google places autocomplete to search for a place, get its polygon region from mapques/nominatim and render the result in google maps.
Here is where I am having difficulties:
...
0
votes
0answers
23 views
Point Within, Query in a buffer polygon in WMS like in ArcGIS ESRI
I need to do a query to filter the result inside a polygon or geometry, like this:
http://help.arcgis.com/en/webapi/javascript/arcgis/jssamples/query_buffer.html
But, i need to do this in a opengeo ...
0
votes
0answers
31 views
QGIS GPS live tracking adding polygon vertices
Maybe I'm missing something or maybe it is a bug? I'm trying to add polygons using the GPS information console. The only button available to record data is "add polygon", but if you click on it, you ...
0
votes
0answers
51 views
Fill polygon with colour depending on the value in MS SQL Server table
I'm using QGIS 1.8. Windows 7. I have a table in MS SQL Server 2008 R2 database with two fields: id and density(int). There are several polygons in QGIS. How can I set color of polygion depending on ...
0
votes
0answers
42 views
Offset a Polygon defined in Lat Lng points by a given distance of miles or km
I am trying apply a positive offset/buffer (enlarge a shape equally from the borders) to a polygon that is made up of a series of latitude/longitude coordinates by a distance that is defined in either ...
0
votes
0answers
20 views
query for adjacent polygons in GRASS?
i need to create a table of each district in india's adjacent districts.
i found this query but couldnt get it to work for me: SELECT p1.PK_UID, p1.Name FROM Polys p1, Polys p2 WHERE p2.PK_UID=1 AND ...
0
votes
0answers
30 views
How to determine if a line is within a polygon or if it exceeds the polygon boundaries?
So I have a polygon layer and a line layer and a point layer...
Each line goes to the centroid of 1 polygon, some of those lines come from within the same polygon, some come from outside of that ...
0
votes
0answers
30 views
Slicing / Cutting a Polygon / Polygon List based on another geometry
I currently use GeoDjango (GEOS, GDAL, PROJ4), I have rather medium set of polygon data (buildings).
To streamline them to a client efficiently (client has a limited viewport) I only want to send the ...
0
votes
0answers
38 views
Selecting a Polygon based on the location of a point
Currently I have a polygon layer made up of three shapes. All the shapes are listed in the attribute table. One of these three shapes intersects a point. I would like to select just the shape that has ...
0
votes
0answers
105 views
How to create polygon with DBGeography Class in Csharp
I want to create a polygon with csharp 4.5 via DBGeometry class.
I found example on csharp to create a point via System.Data.Spatial namespace. (Requires Reference System.Data.Entity)
This code is ...
