A coordinate-based data model that represents geographic features as points, lines, and polygons.

learn more… | top users | synonyms (1)

7
votes
2answers
9k views

How to clip a vector feature to the extent of an existing raster dataset using arcpy

I have a clipped raster dataset with polylines (from the contour tool) overlayed (see attached). I am trying to clip the polylines to the extent of the raster dataset, which seems simple enough, but ...
7
votes
3answers
3k views

Creating a raster surface of overlaps from vector polygon shapefiles?

Basically what I'm trying to do (in ArcGIS 10) is to compare three vector files in order to create a 'comparison' raster layer. I tried using Data Comparison (under Data Management tools) but it didn'...
7
votes
1answer
3k views

How to remove a vector QgsVectorLayer from QGis python plugin

I managed to add QgsVectorLayer in QGIS through a python plugin, for example: vl = self.iface.addVectorLayer(uri.uri(), layerName, self.dbConn.getProviderName()) But how can I remove it?
7
votes
1answer
2k views

Where can I find a Unesco World Heritage List as boundaries?

I was wondering if anyone knows where to find the UNESCO world heritage list with boundaries? I can extract point data from the json feed for the map on the website http://whc.unesco.org/en/list via ...
7
votes
2answers
391 views

Hashing functions for GIS data

I would like to take geometries from a vector dataset and reduce them to a hash. This hash would then be used to verify the integrity of that data and also identify identical geometries. Do any ...
7
votes
3answers
7k views

Finding nearest raster cell value based on vector point?

I have two layers in ArcGIS: One is a vector point and the other is a raster layer. I want to append the value of the raster data grid to the vector point. The problem is the vector point is away from ...
7
votes
3answers
1k views

How to define layer's CRS and avoid the CRS dialog in PyQGIS?

There is an existing Shapefile, which I want to add. At the moment my code looks like: self.iface.addVectorLayer(self.shpFilePath, "Track", "ogr") It works fine, but i want to define the crs ...
7
votes
1answer
5k views

How to create a point along a line given distance

I have been given a non-spatial database which contains the names of lines which I have a shapefile for. The database also has names of points and the distance of each point from the origin along the ...
7
votes
1answer
206 views

Finding largest number of observations within a given radius

I have the following problem: Given the location of insured properties (say houses with fire insurance), i have to find the largest sum of insured values which fit into a 300m radius. Now, my first ...
7
votes
1answer
461 views

How to use simplify()

i have my Vector Data saved in a PostgreSQL PostGIS enabled Database. The Data im displaying is very detailed, i want to simplify it through the simplify() method of Postgis. I duplicated one of my ...
7
votes
4answers
4k views

How to calculate polygon length and width using open source GIS?

How can I calculate the length and with of polygons using open source tools? By "polygon length" I mean the length of the longest line within the polygon (update: to be correct, I just need the ...
7
votes
1answer
1k views

Is there a way to split polygons by several lines in QGIS?

I have a polygon (.shp) and a line (.shp) layer. I want to split the polygon in several pieces along the lines that overlap the polygon. Afterwards I want to edit each polygon separately (attribute ...
7
votes
2answers
577 views

How to remove long linear strips from polygons?

I have a polygon layer representing impervious land cover. This was taken from a land cover raster dataset. The impervious data represents all impervious surface that is not buildings or roads. I ...
7
votes
2answers
873 views

OpenLayers how to maintain layer ordering while using SelectFeature control

I'd like my map to display a few layers in a particular order. Some of these layers are Vectors, others are XYZs, and some of my Vector layers display attribution. Initial layer ordering works fine ...
6
votes
2answers
12k views

How to connect OpenLayers to PostGIS data?

I have read in OpenLayers how to load KML, GeoJSON etc. vector files in OpenLayers. But how can I connect to PostGIS data. If not, why should I upload my data to PostGIS then instead of directly ...
6
votes
3answers
2k views

30,000 data points… can this be reasonably served using openlayers?

I'm trying to tackle a web GIS problem and need to figure out the best strategy. I have a map with 30,000 cells on it forming a grid for the province of Alberta. I have a list of data points for ...
6
votes
1answer
656 views

How to determine optimal windmill placement to maximize production?

How can I add automatically the maximum number of points (dots) with 6m diameter and 100m distance each point from other into an area. The dots will present the windmill base (6m) and I want the ...
6
votes
3answers
103 views

Select all polygons that are completely within a circular buffer

I made several buffers around some points. Now I want to select all polygons that are completely within this buffer. My problem is that I also get the polygons that are partially outside of the buffer....
6
votes
3answers
1k views

WFS to Vector Tiles

Is there, by some miracle, an existing piece of software which is able to convert a (3rd party, GeoServer) WFS feed into vector tiles? In a utopian world, this would happen on the fly, but a download/...
6
votes
1answer
1k views

Where can I find European City boundary data?

Does anyone know any sources for free European city boundary data? Thanks!
6
votes
5answers
8k views

Merge overlapping lines in ArcGIS

I have a polyline shapefile containing a number of lines, some of which overlap. By overlap, I mean that they follow exactly the same path for some of their route, but also have bits that are not ...
6
votes
2answers
1k views

Does an openlayers vector layer work across browsers?

I was under the impression that it was. Here is my example: <html lang='en'> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>GeoRSS</...
6
votes
3answers
4k views

Easily calculate “roundness/compactness” of a polygon

I am trying to find ways to quantitatively describe the shapes of various polygons. For my project, these polygons represent lakes, rivers, lagoons, and parks. So they can be almost any shape. One ...
6
votes
2answers
1k views

Convert points to lines with Python GDAL

I have a dictionary with points. The points are derived from a raster (see image below). The points are not sorted and are not in order. The dictionary looks for example like this: pointDict = {0: (...
6
votes
3answers
1k views

How to check whether a layer is vector or not in OpenLayers?

am not sure whether this is a stupid question or not.. but I am wondering how to dynamically check whether a layer object belongs to OpenLayers.Layer.Vector class. Thanks for any replies!
6
votes
1answer
304 views

Fast data representation on the vector layers

I have found an interesting article about how HTML5 supports representation on large datasets. Article can be found here. In the article it is said that HTML5 and feature simplification can ...
6
votes
1answer
251 views

GDAL/OGR Determine if dataset is raster or vector

I am writing a script using the GDAL/OGR Python bindings and it is possible that the user may provide a raster dataset or a vector dataset as input. If the user provides a vector dataset, the script ...
6
votes
1answer
249 views

Assigning costs to a road network : use raster or vector?

I have a road network in a PostGis database (db_routing). In another database (db_environment), I have some spatial features of the surrounding environment (trees as points and water bodies as ...
6
votes
0answers
340 views

QGIS: How to reverse vertex ordering in polygons

I am working with an Oracle spatial connection in QGIS through which I am accessing and editing a vector layer. I find that when I edit a geometry, the vertex ordering is reversed (to clockwise in the ...
5
votes
1answer
1k views

Programmable buffers using GDAL and python

Is there a way to programmatically generate buffer layers for vector layers using GDAL and python?
5
votes
2answers
5k views

Reclass for vector data in ArcGIS Desktop?

I've got a vector dataset (in fact, OS MasterMap data) and I want to set the value of a certain field based on the value of another field. For example: Field1 Field2 Building 20 Grass ...
5
votes
8answers
1k views

Any Good Map Rendering Engines for SqlGeometry/SqlGeography

Can anyone suggest good map rendering engines for MS SQL Server Spatial types (SqlGeometry/SqlGeography)? By rendering, I mean plot the geometries to a common image format such as png or jpeg with ...
5
votes
3answers
2k views

How to change layer transparency without changing border lines?

I have a raster image of elevations. I have added a vector shapefile that contains local political divisions. I want to keep the elevation colors, but I want to keep the black lines representing the ...
5
votes
1answer
4k views

Google maps android vector rendering : how do they make it that fast?

Most of the question is in the title. If you are on android (I believe its the same on IOS) and use maps you will notice the quality of the maps app and how the vector maps are drawn in a very fluid ...
5
votes
3answers
5k views

Openlayers remove previously drawn polygon on starting to draw next one

Objective: At any point of time there SHOULD only be zero/one polygon(s) on a vector layer with a polygon control. I need the previous polygon to be removed as soon as user starts drawing the first ...
5
votes
2answers
1k views

Georeference vector linework

I'm new to GIS and a lot of searching didn't answer my specific question so far, so I hope someone can help me here. What I want to do is creating a small web application to visualize election ...
5
votes
1answer
5k views

Change vector projection in Openlayers

I have added vector layer to map: vactorTest = new OpenLayers.Layer.Vector("Editable Features", { strategies: [new OpenLayers.Strategy.BBOX(), saveStrategy], projection: new OpenLayers.Projection(...
5
votes
3answers
6k views

How to combine information from raster and vector layers?

in QGIS I have 1 raster-layer (elevation) and 1 vector-layer (administrative units). Now I would like to be able to query one of the administrative units and see the mean and min/max of the elevation ...
5
votes
2answers
1k views

QGIS affine - form of equation

I am at the mercy of a govt authority who have provided utility information in a cad format with a 0,0 origin and a nonsense grid. About a dozen files, the grid and origin are entirely arbitrary. To ...
5
votes
1answer
3k views

Ol3 displaying a vector layer

I have GeoJson that happily displays on GeoJson.IO that I am trying to display on a Vector Layer on an Open Layers 3 Map. The GeoJSON is in EPSG:4326, the Map is in EPSG:3857. My Code is: view = ...
5
votes
1answer
1k views

Merging and joining two line feature classes while maintaining attributes from both using ArcGIS for Desktop?

I created an event layer using the MAKE ROUTE EVENT LAYER tool based on anticipated scheduled events. The road layer which is the base layer is intact. What I would like to achieve is combine layer ...
5
votes
1answer
6k views

Showing menu based on right click on Point Geometry in Javascript

I have implemented a vector layer(using javascript) in open layers which is having point geometry. Now my requirement is to show menu just besides with the point whenever we do right-click on point....
5
votes
2answers
672 views

Distribute points respect to features using Quantum Gis

I want to know if there is any tool to make points with respect to selected features in a theme? Using: vector, investigating tools, regular points you can do it but not with respect to a selected ...
5
votes
2answers
876 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 ...
5
votes
2answers
214 views

Vectorize cell boundaries in GRASS

I need to vectorize the cell boundaries of a raster map and I have forgotten how to do this. For instance, if I have a raster map of a region that is just map=1 with a cell size of 500m, I would ...
5
votes
1answer
87 views

Aggregating polygons with space between them

Im currently editing a large dataset that has large chunks removed throughout (buffered road network). The areas adjacent from each side have coinciding attributes, but have this large erased area in ...
5
votes
1answer
193 views

Create shapefile of raster outline using python

I want to create a single bounding shapefile polygon of valid pixels in raster data (GeoTIFF) using python. I need something efficient as I need to do this for hundreds of rasters. I had thought of ...
5
votes
1answer
2k views

Create a new vector layer that fills space between other polygons in QGIS

I inherited a clipped (500m radius) land cover map containing vector layers of different land cover categories such as buildings, grass, roads, etc from a colleague. The empty (white) space in ...
5
votes
1answer
374 views

How to cache PostGIS views?

Does anyone knows if there exists a caching system for views or queries in postgis? I have a system that gives information through a webpage using a postgis view as backend. The problem is that, ...
5
votes
1answer
12k views

OpenLayers, zoom to vector layer extent

It seems quite simple thing to me, but I get an error. map declaration map = new OpenLayers.Map('map_element', {... projection : _projObj.mercator, displayProjection : _projObj.wgs84 } layer ...