Tagged Questions

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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1
vote
1answer
31 views

How to perform a cascaded combine from python script in QGIS?

I'm working with a large dataset, and I need to be able to combine up to 400,000 polygons. I have been using the QgsGeometry::combine(QgsGeometry* geometry) function and simply looping over all ...
2
votes
2answers
39 views

How to average values in a point layer with respect to polygon layer in QGIS?

I am new to GIS and have the following problem: I have 2 layers: a point layer with a column that contains numbers (pollution index from specific measurement point) and a polygon layer with different ...
0
votes
1answer
202 views

In DIVA GIS how can I change the polygon co-ordinates of a .shp file?

I am using polygon layers from various sources to create species distribution maps however some of the layers have different polygon coordinates to others, therefore I cannot use them together as ...
2
votes
1answer
53 views

How do I get that polygon from Javascript ArcGIS API?

I would like to have a user draw a Polygon (or Line) onto a web map with the Javascript ArcGIS API drawing tools. For the life of me I can't figure out how to pull that polygon from the client and get ...
1
vote
0answers
141 views

how to automate changing polygon's shape while keeping its area the same and limiting deviation from orginal centroid? [closed]

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, ...
0
votes
0answers
25 views

How to write a point-in-polygon query for Postgis?

I'm trying to write a query in Postgis which will return all rows where a dynamically changing longitude/latitude point resides within the geometric polygon of that row (in the geom column). This is ...
0
votes
1answer
93 views

Aggregate points with same values to polygons

I have a shapefile with 2M measurement points (each measurement point has a resolution of a 1/10). How can I aggregate points around each other if and create polygons out of it? They do not have to ...
5
votes
1answer
91 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. ...
0
votes
0answers
285 views

How to do a spatial join if QGIS 1.8 keeps crashing?

I am trying to perform a simple spatial join (adding polygon data to points) in QGIS 1.8: target vector: points join vector: polygons take attributes of first located feature keep all records ...
1
vote
4answers
57 views

Web service to see postgis polygons

Is there any website or web service where I throw a polygon postgis and he show me on the map this polygon. Example: I put this POLYGON((0 0, 1 0, 1 1, 0 1, 0 0)) and the service show me the ...
0
votes
1answer
17 views

QGIS create point data attribute as the name of the polygon it falls in

I'm working in QGIS with a point data set overlaying a farm with 140 fields. While I can analyse the points from each field individually, I would rather use an awk script to calculate statistics I ...
1
vote
1answer
32 views

Shape Metrics Toolbox or equivalent for ArcGis 10

I need to compute the geometric properties (e.g. contiguity index, dispersion index etc.) of a series of polygons and I would like to use the Shape Metrics Toolbox. I am using ArcGis 10 and the ...
1
vote
1answer
55 views

How to paste pictures into data frame?

I have a polygon feature class and I want to trace (select with a polygon) a picture that is solely comprised of a couple of interlocking letters. In ArcMap when I would do this I would simply drag ...
2
votes
1answer
162 views

Create a square grid polygon shapefile with python

i have the following coordinates minx,maxx,miny,maxy = 448262.080078, 450360.750122, 6262492.020081, 6262938.950073 i wish to create a square grid of size 1 m using python. import math ...
2
votes
2answers
61 views

How to divide a polygon with another polygon

I am working in ARCMAP 10. I am trying to divide a polygon with another polygon. I don´t want to clip any part away, but only divide the polygon? The polygons are stored in two different layers. ...
3
votes
3answers
87 views

How to computational efficiently check if there are any overlapping polygons in a group of polygons?

I need to do some processing with groups of polygons. If any of the polygons in the group overlaps other polygon the result is unpredictable and don't throw any error. So, I need to detect if there is ...
2
votes
1answer
42 views

How to Create Touching Multi-Part Polygons?

I have a set of parcels as illustrated in the image below. There are currently no multi-part features in dataset. What I would like to do is to merge (not the right word) all of the parcels with same ...
3
votes
1answer
70 views

digitizing (tolerence) error in line data

I have designed a large number of boundaries. For accuracy, I took lines in patches from different data sets and merged them into one. Now I want to turn them into polygons from lines. I every second ...
1
vote
2answers
46 views

How to convert self intersecting polygon to multipolygon?

Working with the union and polygonize methods in GDAL/OGR, I often end up with self intersecting polygons. The case is one polygon which essentially consists of two polygons: In the above example, ...
1
vote
1answer
33 views

Remove parts of line that fall within a polygon

I have a polygon and two lines. How can I remove the portion of each line that falls within the polygon? # polygon coords <- matrix(c(-1.798123, -1.793072, -1.805767, -1.804129, -1.798123, ...
2
votes
2answers
37 views

Detecting ring direction of a polygon using ArcPy

I am using ArcPy in ArcGIS 10.1 to process some geometry using the arcpy.da data access module. However I have run into a problem with complex Polygons that contain inner rings/holes. From the ...
0
votes
2answers
80 views

Find and list all polygons that overlap with another polygon

I am working with two polygon layers which overlap but are unrelated (one is congressional district boundaries, the other is MPO area boundaries). I would like to generate a list of all the ...
3
votes
1answer
97 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 ...
1
vote
0answers
23 views

Commit Feature WPS Split process

I develop a WebGIS application with GeoServer (2.1.1) and GeoExt (with the last version of OL). Data (polygons features) are stored in a postgis DB. I've implemented editing tools that allow users to ...
2
votes
2answers
82 views

How to make mapable geo data from a solid jpg/png

I have a bunch of hardiness zones, as you can see here: http://mangoly.herokuapp.com/workroom/googlemaps/zones/ They are solid colored PNG images. I know the geo coordinates of the bottom left hand ...
1
vote
1answer
55 views

Control view of Multi polygon in Google map

We have multipolygon WKT. We have no issue to draw all of them in Google map. Below are the codes. The only issue is that we want only the first polygon to be visible but the rest to transparent. How ...
5
votes
2answers
82 views

How to speed up the plotting of polygons in R?

I want to plot the country borders of North America over a raster image depicting some variable and then overlay contours on top of the plot using R. I have been successful in doing this using base ...
1
vote
1answer
38 views

For each polygon, return yes/no value if it intersects another layer

I have a polygon grid overlaying several other polygon vectors. I wish to visit each polygon in the grid and ask yes/no if each of these layers fall within the grid cell or not. I can do this easily ...
2
votes
0answers
100 views

Divide polygon layer by point layer in QGIS?

I have two layers - one polygon layer that is a buffer of a road layer, and one point layer that shows certain locations along that road. What I want to do is to divide/split the polygon layer at the ...
0
votes
1answer
51 views

Knowing the polygon id and getting the extent [duplicate]

I have a text box where I have the polygon Id like, "id_of_the_polygon_12345". Is it possible to get its extent and zoom onto it? I have figured out how to do it upon clicking on the map. But could ...
0
votes
0answers
52 views

How to set point / line / polygon color and transparency with Python?

How can you set the color and transparency of a vector layer feature in QGIS using Python? Seems like a pretty simple and common task but I can't seem to find answered questions or examples. Any ...
4
votes
1answer
313 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 ...
3
votes
1answer
465 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?
7
votes
1answer
235 views

How to rectify polygon shapes in QGIS?

I have some polygon-shapes in qgis-1.7.0 and want to ensure that every polygon is a rectangle. See image below. Is there any way I can do this in QGIS (or any other f/oss)? Or how can I improve my ...
0
votes
2answers
36 views

How to scale/reduce my polygon without changing the central lat & long?

I am writing a VBA code to resize my polygon, I get a input as vector points(Shape file). The code below resizes it as according to my scale factor but my central latitude and longitude are also ...
4
votes
1answer
99 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 ...
0
votes
1answer
56 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
2answers
43 views

Zooming into a particular polygon

I am getting the polygon id by doing identifyParams.geometry = evt.mapPoint; identifyParams.mapExtent = map.extent; identifyTask.execute(identifyParams, function(result) { var i; var ...
4
votes
2answers
58 views

“GIS” Mapping on Monument - Scaling

I have a Baroque tombstone for which I have to map the damage phenoma. Normally one can use a vector drawing programm but one has always two boundaries between the different polygons. Questions: Is it ...
1
vote
2answers
107 views

Using the ArcGIS Runtime SDK for C# is there a method to Hit Test for a polygon on the graphics layer?

I am very new to using ArcGIS runtime SDK for C#. I have loaded a polygon from a shapefile. I wish to query if a lat/long point is inside or outside the polygon? How can I do this? Thanks in ...
3
votes
1answer
67 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 ...
1
vote
0answers
56 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 ...
14
votes
2answers
810 views

Is it possible to gray out a Google Maps map except for some area?

What i am looking for is a way to emphasize a certain area on a Google Maps map by graying out the rest of the world. I heard about some solution of using 2 polygons of which 1 is visible and the ...
1
vote
1answer
392 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 ...
0
votes
0answers
44 views

polygon/raster intersection artifacts

I'm intesecting a polygon with a raster using PostGIS > 2.0. The outer boundary of the polygon is formed by the convex hull of polygons (building outlines plus safety margin) and the inner rings are ...
8
votes
1answer
119 views

How to automatically reduce polygon size?

I am working with two polygon layers (counties & states) which I will 'intersect' to find which counties are within which states. Due to data inaccuracies I have to change all county polygons and ...
5
votes
2answers
155 views

inner convex-hulls in a set of 2D points

A set of 2D Points are scattered randomly (i.e., no specified pattern), we are interested in finding all inner-convex-hulls (ICH) in an order of largest in area to a minimum until the entire study ...
5
votes
3answers
163 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 ( { ...
0
votes
0answers
30 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: ...
5
votes
3answers
460 views

How do I use polygons to apply a unique value to all raster cells within those polygons?

In ArcGIS 9.3, I have a raster file that I would like to "mask" with polygons, giving a single value to all the raster cells that overlap the polygons. How can I do this? Here's a screen shot, where ...

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