Tagged Questions

A region enclosing a point, line, or polygon at a specified distance.

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12
votes
3answers
2k views

How to create one-sided buffers or parallel lines in PostGIS?

I'm looking for a way to create so-called one-sided buffers or parallel lines in PostGIS. Example: 1. buffer, 2. one-side, 3. both-sides I've found some discussion on the mailing list from 2009 and ...
12
votes
5answers
606 views

Simulating the expansion of polygon features

I've got what I'm hoping will be an interesting question. I'm working on an assignment for an intro to GIS course that uses some Gulf oil spill data to introduce common vector-based spatial analysis ...
12
votes
2answers
475 views

ArcGIS Buffer accuracy problem

world, once again I encounter something very strange with ArcGIS. I perform a buffer analysis on one side of a polyline. There seems to be a serious accuracy problem and I can't figure out what the ...
9
votes
4answers
500 views

How to buffer in pyQGIS?

I'm looking for some examples to do simple python scripts in QGIS. How would I do a buffer analysis on a dataset? I can't seem to find much in the manual and QGIS python that quite matches the Esri ...
9
votes
2answers
344 views

How to buffer a line with different distances for left/right sides

How can I buffer a line in QGIS using one attribute for the left side of the line and one attribute for the right side of the line? I am trying to buffer a river with its bank width, which is ...
7
votes
2answers
743 views

Create “Inner Buffer” in ArcGIS

I am currently searching for a possibility to create an "Inner Buffer" in ArcGIS. I have a lot of polygons (houses)(in one feature class) and one big polygon (in one other feature class). I want so ...
7
votes
2answers
318 views

Growing a PostGIS geometry by a percentage

I'm looking for a way to add a buffer around a PostGIS geometry, but the size of the buffer should depend on size of the geometry. That is, I want each geometry to be enlargened by, say, 5%. The idea ...
7
votes
3answers
816 views

Use buffer tool to draw different radii?

I am new to Arcmap-Arceditor 10 and could really use your help. I have been mapping ethanol plants (which utilize corn to produce ethanol) and corn production amounts in the counties of the USA. ...
7
votes
3answers
315 views

Is there a st_buffer inverse function, that returns a width estimation?

When you supply a geometry g1 and a width w to the standard OGC function ST_Buffer, it returns a new geometry g2, g2 = ST_Buffer(g1,w) This question is about the inverse: a function where you ...
6
votes
2answers
334 views

What's the Workflow for buffering in meters/km using WGS84 layers?

I'm a little bit new to GIS, so bear with me a minute.... I'm using QGIS 1.7.4-Wroclaw and working with an SHP layer in WGS84. I want to buffer out to a certain number of kilometers from this layer ...
6
votes
1answer
202 views

QGIS define hexagon area around mapped points

I am using QGIS to map a number of radio antennas (for mobile network). Once I have the layer of the sites (done), I would like to assign to each site a coverage area (envelope). I could achieve that ...
6
votes
2answers
559 views

How to buffer a vector shapefile using ogr python?

I am trying to learn how to use ogr in python using the country and populated places datasets from http://www.naturalearthdata.com/downloads/50m-cultural-vectors/. I am attempting to use filters and ...
6
votes
1answer
207 views

How to generate non-merging buffers in QGIS?

I'm using QGIS to construct some fixed width buffers from a coastline shapefile. Is there a way to easily handle overlaps/ median lines? (I'm not sure if there's a particular term or phrase I should ...
5
votes
4answers
1k views

ArcGIS Buffer/Dissolve performance

I'm wondering if anyone else has experienced significant performance penalties when using the ArcGIS buffer function with the 'dissolve' option on point features. My dataset is a shapefile of 260 ...
5
votes
3answers
324 views

Is it possible, in QGIS, to create buffers with a set radius, but with individual values taken from the attribute table?

I am looking to create an output that consists of an 11KM buffer around a number of discrete points, where the buffer has a value defined by a column in the data sets attribute table. Is this ...
5
votes
1answer
2k views

What is up with QGIS buffer tool units?

I have been trying to figure this out for a couple weeks now and have had no luck getting the buffer tool to accept anything but degrees as units of measure. I have found lots of stuff saying the ...
5
votes
1answer
722 views

How to calculate the size of a particular area below a buffer in QGIS

I have a point shapefile of villages where data was collected in Northern Kenya. I created a buffer around those villages. The second vector layer contains polygons defining areas according to ...
5
votes
2answers
148 views

Using newly created features in the next part of a python script

Good Afternoon I am trying to write a python script which buffers a large number of features from a geodatabase (but not all) and then dissolves the newly created buffer shapefiles together. ...
5
votes
2answers
219 views

How can I create a “setback” buffer in QGIS?

I've been going a bit crazy in trying to create a "setback" buffer on QGIS for coastal lines in a map projecting this buffer outwards towards the sea. I've managed to create a normal Bidirectional ...
5
votes
3answers
974 views

How can I display with OpenLayers the geometry returned from a ST_Buffer in POSTGIS?

Im using PostGIS, GeoServer and OpenLayers, and the thing is that i want to display the geometry result from a query like this: SELECT ST_Buffer(ST_GeomFromText('POINT(100 100)'), 500); To perform ...
5
votes
2answers
421 views

Create a polyline buffer with Arcpy

I'm trying to write a python script with ArcPy that draws arcs and I've achieved something with creating a buffer and then clipping it with a bounding box so I only keep the length I need (I thought ...
5
votes
1answer
1k views

ArcGIS: inside buffer with attributes?

How can I create buffers for polygons that a) lie only inside the polygon boundary, and b) know who their parent is? An example of where this is useful is First Nation Traditional Territories. There ...
5
votes
2answers
298 views

Dissolving polygons by attribute and in a certain distance (ArcGIS)

in a FeatureClass I have a lot of polygons which contain attributes of different landuse-types. Now I am trying to dissolve those polygons of the same landuse-type, but only if the distance between ...
5
votes
1answer
150 views

What is the width of the beach of a little island polygon?

This is a "classic" problem, that have no practical utility (see note-1 for applications), but illustrate another GIS problems... We can do some approximations to modeling the situation, the real ...
5
votes
1answer
206 views

What is the unit of measurement for buffer calculation?

What is the unit of measurement used by Geometry class for it's buffer calculation ? Api doc currently defines it as " distance - the width of the buffer (may be positive, negative or 0)" I need to ...
5
votes
2answers
838 views

Need help calculating forest cover within a buffer when it overlaps with other buffers

I'm new to ArcGIS and having real trouble getting this done… Hopefully someone can help. Thanks in advance! I have a layer showing forest cover in a landscape. I'm trying to create a 5km buffer ...
5
votes
1answer
107 views

How do I find location of minimum value within a buffer (around a point)

I have a digital elevation model (DEM) with a point location defined. I want to locate the lowest height values at a set distance from this point. I envisaged creating a buffer around the point ...
5
votes
1answer
177 views

Geodesic buffers for polygons

How can I create geodesic buffers around polygons? I'm on 9.3.1 ArcMap, but I need a programatic solution. IBUfferConstruction only does geodesic buffers for points. What are my options?
4
votes
3answers
3k views

Creating a square buffer around a point feature in ArcMap

I would like to create a square buffer from a point feature. I do not understand the code that gos into it. This similar questions as asked on the forums.esri website but that was over 10 years ago. ...
4
votes
3answers
925 views

When should I use ST_Buffer?

I would like to know what is the sense of using st_buffer operation. In PostGIS reference guide there is only the syntax and a short description of this operation. Could you give some examples to ...
4
votes
2answers
990 views

Multiple ring buffer with attributes

Building on ArcGIS: inside buffer with attributes?, I'd like to be able to create multiple ring buffers, while retaining (and possibly dissolving on) attribute values. How can this be done?
4
votes
2answers
251 views

memory issue when trying to buffer/union large dataset using postgis

I am trying to generated a dissolved buffer of a large point dataset (Ideally 29 million points - Address data in Great-Britain, but I receive the data by chunks of 1 million points, so these could be ...
4
votes
1answer
157 views

Surface covered by buffers in QGIS

In QGIS, I have plotted buffers around points. I would like to calculate the area which falls under buffers without over counting due to buffer overlaps. Is there a quick and easy way to do this?
4
votes
1answer
1k views

Best way to get Convex Hull/Boundary of millions of points

I've been trying to do some point analysis on some xyz data, I'm at the point where I've decided it is best to produce a boundary of my xyz files and put this with the metadata for each survey. Now ...
4
votes
1answer
1k views

Circular buffer with QGis

I would like to select areas under a particular circular radius in QGis. I believe this is accomplished with the buffer tool, but when I specify the radius the area is not circular. How to make it ...
4
votes
1answer
88 views

Distance from waterways

I have an sdc file with water bodies, i.e. oceans-rivers-lakes. I want to combine it with a shapefile with the boundaries of countries all over the world and produce two measures: 1) The average ...
4
votes
2answers
168 views

PostGIS algorithm to unite points of two geometries that are within specified radius

I want to find an PostGIS algorithm to unite points of two geometries that are "near" to each other. That is: I want a function, that takes as input two geometries, and returns 1 geometry, that ...
4
votes
2answers
281 views

How to invert a Buffer(get the inside of a ring buffer)?

I have a line layer of a road network around which I create a buffer zone of 1000 m with Analysis Tools>Proximity>Buffer. But I am interested in the areas outside the buffer zone, and not the buffer ...
4
votes
1answer
255 views

Select points within 2 buffers

I have 2 huge files of points (hundreds of thousands of points). I need to determine a way to loop through all the points in one file and find all the points in the second file that are only a ...
4
votes
1answer
282 views

automating forest cover calculations with Python

I have a layer of forest cover comprising ~ 30,000 individual forest patches, and I need to calculate the amount of forest cover within a 5 km buffer of each patch. The buffers all overlap each other, ...
4
votes
1answer
62 views

How to create fixed length (and width) buffer around a polyline in ArcMap 10?

Could someone please help me? I would need to create 100 buffers (500m x 1km) along a stream polylines. I know how to do it by using shortest distance but the buffers should follow the curves of the ...
4
votes
2answers
142 views

How to join number of point features into attribute of nearest line segment

I have point shapefile with lot of attributes, that represent road accidents and line shapefile with highways. What i want is to join attribute into line shapefile with value, that represent number of ...
4
votes
1answer
159 views

How can I create a pollutant dispersion raster in QGIS?

As my previous questions have indicated, I am working on an air quality problem where I have a dataset of industrial emissions that consists of a location (long, lat), and an annual volume of ...
4
votes
0answers
102 views

Getting buffer wizard-like speed in Python (vs using MultipleRingBuffer_analysis)

I've got a script that takes a single input polygon feature, throws 10 buffers around it at tenths of a specified input distance, and then symbolises the output based on an existing layer file. ...
4
votes
3answers
1k views

Conflicting measurement units with buffer ftools

I am new to qgis and I would like to create a buffer around point features. My goal is to create a quarter mile buffer (402.336m) around each point feature, using Geoprocessing Tools -> Buffer(s), ...
3
votes
2answers
466 views

Generate non-overlapping shapes from a buffer

I have a collection of points, and I need to generate shapes around these points. Let's assume that these points are locations of offices and that the shapes are the 'area of responsibility' around ...
3
votes
2answers
221 views

Is there a way of doing a statistical analysis of buffers?

I am doing a buffer analysis of incinerators and looking at the output areas within those buffers, is there a way of doing a statistical analysis of several buffers to see if there is a significant ...
3
votes
2answers
2k views

How can I use the Buffer Wizard in Modelbuilder or arcpy? (ArcMap 10)

I am creating a model in ArcMap 10 and I need to use the Buffer Wizard tool to create multiple buffers within a polygon feature class. The problem is, I can't seem to place the Buffer Wizard within my ...
3
votes
3answers
205 views

Buffer with physical barrier

I don't think is possible, but I'm looking for a way to stop my buffer at a certain physical barrier. For example, I have point near a river and I'm creating a buffer around my point that is larger ...
3
votes
3answers
496 views

Is it possible to create multiple buffers using QGIS?

I'm new to QGIS and have no programming skills, is there an easy/uncomplicated way to create multiple buffers around a line feature.

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