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Questions tagged [vector]

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

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12
votes
2answers
2k views

Tiling Vector data without losing geometrical and topological information

I am trying to figure out a way to sub-divide a vector based map into smaller blocks. I can tile the map based on different strategies such as q-tree. However, it is unavoidable to cut some polylines ...
14
votes
1answer
2k views

What is the best way to represent bridges using a point vector layer in QGIS?

I'm working on a hiking/biking maps of trails in the woods which sometimes have bridges that need to be shown on the map. I'm trying to figure out the best way to capture and represent them using QGIS ...
9
votes
2answers
470 views

What spatially-aware GUI administration softwares exist for PostgreSQL/PostGIS?

Most of my experience with PostgreSQL has been pgAdminIII and psql, but I'm interested to know what others use. Is there PostgreSQL equivalent to SQL Server Management Studio (SSMS) and its ability ...
6
votes
1answer
2k views

Representing overlapping polylines in QGIS

I have several shapefiles representing bus lines with different colors for each segment, however, because the lines are exactly superposed, only the shapefile on top can be seen. Is there a way to ...
6
votes
2answers
5k views

OpenLayers - Get features inside a polygon

In my OpenLayers map I allow users to draw an ad-hoc polygon vector. Then I need to get all the features from a WFS vector layer that fall within the ad-hoc polygon. Here is the code I have that ...
4
votes
4answers
1k views

QGIS classifying vector data

I am trying to classify a shapefile based on rule set, following this tutorial. This is the result: What I want to ask is: 1. How to insert the classification result (water, land etc) into the ...
4
votes
1answer
592 views

Raster to vector with gaps in Landsat ETM

I need to find size of water area from a raster (jpg) using QGIS 1.8.0-Lisboa. The raster is a Landsat image with gaps of data in it. I used Polygonize, but the output file shows wrong polygon size ...
3
votes
1answer
963 views

How to reproject all the vector files in a folder to a particular projection using ogr2ogr?

We have a folder with all sorts of vector files like tab,shp,dxf. Many of the files are in different projection. I would like to convert all the files to EPSG: 4326 and eventually the non-shapefiles ...
1
vote
1answer
6k views

Openlayers get coordinates of a circle vector after draw

I have made a openlayers map. I have made two features on the map. Navigate DRAW POLYGON I have made 40 sides to my polygon which turns out to be a circle. After I have drawn my circle I want to ...
10
votes
2answers
457 views

Styling specific layer by using polygon mask in QGIS?

I have a line layer and a polygon layer in QGIS: I would like to style the part of the line layer outside the polygon using one style and the part inside using a different style: I don't want to ...
7
votes
5answers
6k views

Calculating 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
14k views

QGIS: “Invalid geometry” even after using validity checker and v.clean

I'm trying to intersect two layers in QGIS, similar to this unanswered question. I've performed Vector > Geometry Tools > Check Geometry Validity and I've run GRASS's v.clean, per these questions. I'...
6
votes
1answer
2k views

Seeking European City boundary data?

Does anyone know any sources for free European city boundary data?
4
votes
3answers
2k views

DXF to georeferenced SHP

I know how to set projection and georeference bounds of scanned TIFF file, by using gdal, but I don't know how to do the same for vector file. For example I georeferenced TIFF file by using this ...
4
votes
1answer
1k views

How to change layer symbology in QGIS 3 with QgsFeatureRendererV2?

I am updating a QGIS plugin from QGIS 2 to 3 and I am struggling with changing the layer symbology (a single symbol type for a line layer). I would like to have all lines in my layer to have the same ...
3
votes
2answers
128 views

QGIS how to sum a certain vector field inside a polygon and populate a field in the polygon?

I have a polygon with vector point civic addresses inside it. Each civic address has a different number residence. I want to sum the total number of residence inside that polygon and it populate a ...
3
votes
1answer
2k views

PyQGIS: Change attribute value doesn't work, results in NULL

I am writing a QGIS plugin, which at one point attempts to change several attribute values on a layer. However, in the end no changes are made. If I punch similar code into the built-in Python Console,...
2
votes
1answer
983 views

Show alternating contour lines

Is it possible to show only every other contour line? And how do you do that? (I'm new to QGIS Lisboa 1.8.0, but even newer to QGIS Dufour 2.0.1, but have used ArcGIS a bit a while ago, and also ...
10
votes
0answers
4k views

Import Vector data to QGIS from pdf and apply georeference [closed]

I am Using QGIS 2.14. I have a PDF created by Mapinfo, it contains multiple layers of vector data that I can open as separate vector layers in QGIS. However no map projection data was saved to the ...
6
votes
3answers
429 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....
5
votes
2answers
2k views

Spatial query of raster data using QGIS

I have population distribution data as a raster layer and exposure contours as vector (polygon) layers. What I'd like to do is use the vector layer to estimate the population indicated from the raster ...
4
votes
1answer
483 views

Simple way to compare ranges and distributions of species, looking for correlation and differences between ranges

As a biology student just beginning with GIS, wondered if someone could give me an idea of what tools to go about using to compare the range of 3 species that have trophic effects on one another. I ...
3
votes
1answer
2k views

Save map in raster format from QGIS using compression

Is there a method to save a map in raster format from QGIS using compression? For exemple from "Export map" in ArcGIS there are many options to compress the images depending on the file type (tiff, ...
3
votes
1answer
2k views

How to get smooth contours from points or IDW raster in QGIS

Hello I'm an artist trying different ways of drawing contours in QGIS using points with income values. I've been able to import a shp file with the data, create a layer with centroids of the census ...
3
votes
1answer
3k views

OpenLayers: make polygons not zoom

I have a simple OpenStreetMap for which I want to display a series of circles. Each circle represents readership for that area, so its radius will change based on the numbers. However, when I create ...
3
votes
1answer
2k views

Deleting points which are close to each other

I have a vector file containing thousands of points. Where points are within x distance from each other, I wish to delete one of the points and keep the other (either by snapping to one point, or ...
3
votes
1answer
836 views

Assigning raster values to line and polygon by QGIS?

I have a raster data(.tif), and would like to assign its values to line and polygon data by location. Here, I'd like to take min, max, mean and median. There is "Join attributes by location", but it ...
3
votes
1answer
208 views

Exporting crown boundaries from tree segmentation in R?

I am using lidR package to segment my trees using lastrees directly from the points clouds. The function works fine, however I would like to export to vector file the canopy boundaries from ...
3
votes
1answer
445 views

How to calculate the percentage of a Line through Polygons?

I have a straight line which runs through a bunch of polygons, which don't have spacing between them (border to border). Is there an easy way with QGIS to calculate which polygons it passes and by ...
3
votes
1answer
4k views

Reproject a vector layer (EPSG:27700) using WFS onto a googlemaps background (EPSG:900913)

I have the following HTML-JavaScript code and I have problems re-projecting the vector layer (WFS) from EPSG:27700 (British National Grid) to EPSG:900913 (Google Maps). I managed to project the WMS ...
3
votes
2answers
408 views

Add overlapping polygons

I have a feature class that contain many overlapping polygons. Each polygon has a field value which I would like to add together wherever the polygons overlap. There are about 100 polygons each with ...
2
votes
1answer
217 views

Keeping a vector layer always on top

I want to know how to keep a layer always on top of other layers! After adding a vector layer ( QgisInterface->addVectorLayer ), I want that layer to always be displayed on top of layers added later. ...
2
votes
3answers
8k views

Openlayers get coordinates from polygon

please could someone help me and bless me with an example of how to get coordinates from a polygon in OpenLayers?
2
votes
1answer
261 views

Rasterize points in a map : result is not leasible. How to make the raster (points) bigger?

I have a vector layer (points) that I rasterized based on one attribute of the vector layer. I chose the GRASS GIS 7 command : v.to.rast.attribute. The raster layer appears in the map, but is not very ...
2
votes
0answers
922 views

Create map (image) from raster and vector in Python - problem with big files

I wrote function which allows me to plot raster and (optionally) plot vector on the same image. It works for small files, but in case of big rasters, I receive memmory error. I've tried to add ...
2
votes
2answers
2k views

Styling OS Vectormap Local in QGIS?

I am attempting to style Ordnance Survey Vectormap Local on QGIS 1.8.0 by using the styling sheets suplied by Ordnance Survey. The styling sheets are available from the OS website (http://www....
2
votes
1answer
874 views

PyQGIS in standalone script, vector loading error

I am trying to use the QGIS functions in a stand alone Python script. I'm running Mountain Lion OS, 2.7 Python & the QQGISis 2.0.1 Dufour. My main problem is that I cannot get started - I cannot ...
1
vote
2answers
835 views

QGIS 2.0 Automatic generation of a vector layer out of a point layer

I am an environmental engineer and the aim of my QGIS 2.0 project is to visualize the results of a sewage water system inspection. In a first step I included the hoppers from a csv file and added a ...
1
vote
2answers
1k views

How to combine two polyline shapefile together

Here is my question Two shapefile: * A: represent the outer boundary of the city area * B: represent the inner boundaries of the city divisions. I want to * Combine these two shapefile * ...
1
vote
3answers
5k views

How to show vector features in OpenLayers after hiding it?

I did change some vector features style (through check-boxes) using style property : var features = layer.features; for( var i = 0; i < features.length; i++ ) { //features[i].style = { ...
1
vote
2answers
307 views

Free 3rd party library for showing geospatial vector information

Up to now, I have used GDAL to extract raster data from geotiffs and then, OpenGL to show that raster data. But when it comes to extract vector data with the help of OGR, what library would you ...
1
vote
2answers
1k views

Is it required to use BBOX strategy with WFS protocol in OpenLayers 2?

is it a must to use BBOX strategy with WFS protocol in Vector layers ? I cannot display this layer without BBOX strategy: vLayer = new OpenLayers.Layer.Vector("Test", { styleMap: new ...
1
vote
1answer
2k views

How to automatically transform between base layer and vector layer in OpenLayers

I have a simple example on http://jsfiddle.net/29bsw/ I have a map with an OSM layer as base layer and an additional vector layer. The projection of the map is defined as EPSG:900913 and the ...
1
vote
2answers
669 views

QGIS point sampling tool really slow for polygons?

I have a large field of randomly distributed points (100,000 of them to be precise), and I'd like to get values for a variety of raster and polygon coverages for each point. I've been using the QGIS ...
1
vote
0answers
704 views

How to read vector datasets using GDAL library

Up to now, I have used GDAL in order to read raster information and geotiffs and show them with the help of OpenGL. Now I have a vector dataset, and by that, I mean I have the files with types: DBF ...
6
votes
1answer
3k views

Loading a multipoint shapefile in R

This issue has only been raised in the community once, two years ago, to the best of my knowledge. I think it's high time to raise the issue again! readOGR, from the rgdal package, cannot handle ...
6
votes
2answers
876 views

Calculating average raster to point distances within census tracts

I have some experience using ArcGIS, but mostly with the field calculator in the attribute table/spatial joins, so I apologize if I say something that doesn't make sense. To provide a bit of ...
6
votes
1answer
3k views

How to merge overlapping and duplicate lines from vector layer to one single line?

I used the "polygon to line" tool from QGIS, to get a line-layer from this polygon-layer: Unfortunately this causes overlapping and duplicate lines, after I broke the qgis-export via GRASS into ...
6
votes
1answer
667 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
1k views

How to emulate a specific vector grid in QGIS?

I would like to analyze data included in a pdf file. The file contains information on characteristics of 16km grid cells for a specific study area. The file also includes a map displaying the grid. I ...