QGIS is a user-friendly, cross-platform GIS application licensed under the GNU General Public License.

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104 views

Raster area (QGIS) problem explained

I would like to know the area that each value in a raster has... The raster I have has values from 2-15 and I would like to know the area that each value is occupaying within my polygon... Thanks! I ...
2
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3answers
302 views

How to route railcars along railroads?

I'm very new to the world of GIS, but I'm learning a great deal from this site, as well as others. I fell like this should be 'easy' but I need to be pointed in the right direction. I'm trying to ...
2
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1answer
1k views

How to create a line in a given distance to an existing one?

I am looking for a possibility to create a second line in a given distance to an existing line. The existing line is curved, so simply create parallel line segments with CAD tools will not work. Any ...
2
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2answers
617 views

Trimming Specific Text Values in QGIS Field Calculator

Sorry if this is a dumb question, but I am wondering if there is a way to copy the text from one field to a new field, but eliminate specific words. For example: **Old Field** ...
2
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0answers
310 views

How to create polygon “stamps” and extend lines by fixed distance? in QGIS

This is related to Does QGIS have these CAD editing functions? Cadtools have solved a lot of the issues I had but I need the ability to see how long a line is while I am drawing an orthoganal ...
2
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2answers
262 views

different labels at various scales

I have a locality layer of neighborhoods and suburbs from a spatialite database. How do I label this single layer with the neighborhood name at a lower scales, but as I zoom out, I would like the town ...
2
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1answer
4k views

Convert a Tif raster file to vector shp file in QGIS

So I've been trying to convert a georeferenced Tif raster file into a vector shp file using QGIS. It's seems to complete this but it ends up giving me a feature class that has over 500,000 features, ...
2
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1answer
333 views

How do you calculate positional accuracy in qgis?

How to you compare two layers in QGIS to get the positional accuracy?
2
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2answers
278 views

Losing large portions of elevation contours from QGIS to PDF

Please forgive me as I'm new to GIS and all this might be a silly question, the wrong place for this question, or a hack way of going about what I'm getting at. So any suggestions on better practice ...
2
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1answer
2k views

QGis failed with error: latitude or longitude exceeded limits

I have some shapefiles from vegetationtypes in QGis and i wanted to put a googlemap in background, so i installed the open layers plug in. But every time i tried to load the map, theres an error ...
2
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1answer
570 views

How to show labels depending on the zoom scale and save it forever in one project?

I have got a problem in showing labels for a polygon layer : When I select "Show labels" in the layer's properties, then I select that I want to use the scaling to show or not my labels and I ...
2
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1answer
632 views

QGIS 1.7.1 and PyQT4 conflict: what am I doing wrong?

I've just started playing with QGIS with a view to eventually developing a few simple plugins in Python. I downloaded QGIS 1.7.1 for Windows and started working through these workshop notes. If I've ...
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3answers
253 views

How to clean/edit GPX (tracks) files recorded from GPS device?

During a long trip, I have recorded tracks of my journey with the GPS of my smartphone. I have ended up with about 30 GPX datafiles. Now that I am back, I am trying to draw a map of this trip. I ...
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1answer
146 views

PyQGis - Working with Spatialite

I wrote a Vector layer to a spatialite file/db using the dedicated API tool, using valid driver names supported formats by OGR. When connecting to that db, I can't retrieve properly the geometry ...
1
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1answer
139 views

How to exactly georeference in QGIS

When I georeference a raster image in QGIS, it's always a bit displaced as in the attached image (the cyan polygon is the template, the red border is the georeferenced image), although I try to set ...
1
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1answer
161 views

QGIS Model Builder Script - Possible to merge layers in a folder?

I would like the user to select a folder via the interface in which all the vector shapefiles inside that folder would be merged. I have been using the Model Builder and looking at example scripts ...
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2answers
108 views

Open mail client when clicking feature in Attribute Table

One of the attributes/features of my layer contains an email address. I'd like to be able to open the default mail client by clicking on the mail address from the Attribute Table. After some initial ...
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1answer
68 views

Create and immediately update field using Field Calculator

You can create fields and once created, populate them with data using the Field Calculator. But can you do both at the same time using an expression? Or must you do it in 2 steps?
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1answer
248 views

Adding attribute list to combobox in a python plugin

I am developing a simple plugin at the moment which contains 3 combo boxes: comboBox_1 comboBox_2 comboBox_3 Combobox 1 & 2 lists the vector layers available, however I would like the 3rd ...
1
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1answer
71 views

Why do the raster band values have different values than the raster statistics?

I am working on a raster file (1 Band). According to the raster metadata, my minimum value is 0 and maximum is 7458. This seems to be confirmed by the Style options that return some category values ...
1
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1answer
112 views

Is it possible to run qgis through python?

I need to build an app to analyze some raster layers in qgis. I thought it was possible to just write code in python (2.7.6) (IDLE) and let it automatically open QGIS, load some layers, do a distance ...
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0answers
142 views

Load MrSID file in QGIS 2.2 on Ubuntu 13.10

Is there a way to do this? I have tried a number of the write ups on this, and it appears that libgdal-mrsid-src no longer exists. Is there any other workaround? USDA NAIP imagery is sent as MrSID.
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0answers
160 views

how to add polylines(routes from public transport) on postgresql(pgrouting) with GUI

After searching a several long time... i decide to ask here for help, im currently using ubuntu 12.04(because of compatibility) with postgresql 9.1, postgis2, pgrouting2 and qgis2.2 i need ...
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2answers
636 views

How to resize symbols in the QGIS Print Composer legend?

I am trying to map a count data type via graduated symbol against a chloropleth and the legend is too big. The circles of the graduated symbols are the actual size of their corresponding values in ...
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2answers
243 views

Draw great circle rays from a single point along specific directions

How can I draw great circle rays starting from a single given point P (for example, from coordinate [34 N, 116 W] in this map) and along directions D1, D2, ... (for example, 30, 45 and 135 degrees) in ...
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1answer
208 views

How to get additional subbasin areas designated by points in the river network?

Update 14/1/9:I follow this post:Watershed and Stream Network Delineation, and here's my workflow: use Batch Point Generation to create batch points related to designated points(green dots) Batch ...
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1answer
404 views

How to draw a simple bus network that works with pgRouting?

What I'm I doing wrong? I've created a new shape layer for lines, I've enabled snapping with 5 map units for that layer. When I draw a line between two of the stops I get a purple marker when I'm at ...
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1answer
198 views

How to add the current document path on Print Composer?

I'm trying to demonstrate to my company that we can begin using QGIS in conjunction with (and sometimes even instead of) ArcGIS and MapInfo. I've started setting up some layout templates but have run ...
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3answers
293 views

How to access user credentials in database connection?

I am trying to automate a couple of things when a QGIS plugin is activated: If Layer A is not in the TOC, add it. This requests username and password to access a PostGIS table using the inbuilt ...
1
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1answer
145 views

How to set field values as labels in QGIS2 Print Composer

I am mapping the distribution of 325 bird species, displaying circles in the grid cells each species occurs in. The data contains as many duplicates of the NAME as there are cells in which it occurs. ...
1
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1answer
151 views

Species atlas (how to automate to create on page for each species with QGIS)

With the use of QGIs, I would like to create an Atlas for a batch of species, with: a background with the country (from a vector layer or from the openlayer plugin). a vector layer (polygon) to show ...
1
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3answers
506 views

How to create random point in according polygon for each dataset entry in a list (with R)

I have an area divided into polygons, and a dataset of observations which has a common field with the polygon layer. I now would like to generate a random point for each dataset entry within the ...
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2answers
144 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
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2answers
437 views

What is the equivalent of arcpy “Con” in QGIS and/or R raster-package?

I'm looking for an equivalent of the conditional expression "Con" from arcpy in an open source spatial analysis package. I'd prefer to use QGIS or R. To provide some additional detail, I need to ...
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2answers
317 views

How to add a dynamic timeline to the QGIS canvas?

I am using the plugin Timemanager which works really great but there is one thing I'd like to improve. Instead of displaying the date and time on each frame, I would like to display a timeline ...
1
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3answers
773 views

QGIS 1.8 startup crash - looking for a log file

I have a problem with QGIS 1.8 with OSGEO4W installer (windows 7 - 64 bit). QGIS crash on startup, it shows the splash screen and then nothing. I have updated from an old 1.7.4 QGIS version. I have ...
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2answers
260 views

How to mask out features outside of the Coverage Layer for Atlas plugin? [duplicate]

Using the Atlas plugin for qGIS how do I set the coverage so that it will only highlight the feature(s) I want but still show the surrounding features as grayed out areas? This would have been easy ...
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2answers
1k views

Adding .e00 data into QGIS

I wonder if anyone can advise me on how to go about adding .e00 data into my QGIS project. I'd be very grateful for any advice, or a hint on where to find it. Thanks TVZ
1
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1answer
415 views

how to open layers with multiple geometry types in qgis?

I recently had some difficulties opening some MapInfo TAB vector layers in QGIS because each MapInfo layer contained two different geometry types: point and line. The MapInfo layers had originally ...
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2answers
1k views

Problem loading vector layer (pyQGIS)

I've installed the qgis on ubuntu 12.04 following the instructions on http://hub.qgis.org/projects/quantum-gis/wiki/Download. I am trying to test the Python API and try to do the follwoing from ...
1
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2answers
838 views

Interpolation of contours (from one “main-contour-shapefile”)

I calculated, that the best and smalest possible äquidistance (equidistant) for my map is 30m. After I generlized my DHM, I extracted contours of a intervall of 30m and smoothed them. Now I have my ...
1
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1answer
785 views

Last edited information missing when used QGIS - Dxf to Shp

I am doing as constructed drawings which require the information to be in a GIS system and more specifically drainage as constructed drawings. I must have a separate file for Pipes and Pits. First I ...
0
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1answer
76 views

Blank Shapefile output?

When executing the following command string in the active browser, Qgis projects the triangle polygon and associated attribute table correctly. Upon reopening the shapefile in a new browser, the ...
0
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0answers
81 views

Issues creating slope raster layer from a point layer

I'm trying to create a slope raster layer using QGIS 2.0 on Windows XP. I started with a points layer with the Z elevation attribute. I then used the interpolation plugin to create a DEM. But, ...
0
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2answers
119 views

Calculate length of line across zones with at least m accuracy

I have created lines between multiple points that are across MGA 54 and 55S (EPSG 28355). I am trying to calculate the distance between points but different methods give different answers (~1km ...
0
votes
2answers
295 views

“Identity” overlay in QGIS?

I have two polygon layers I'd like to overlay using QGIS or another open source tool. What I want as output is a polygon layer with the extent of one polygon, but with each polygon in that layer ...
0
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1answer
991 views

Can not make qgis.db private copy

I've just installed Qgis 2.0.1 and the above error message appears. Does anyone know how to resolve this problem? I think I need to change the permissions of the relevant folder, but I'm not ...
0
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2answers
99 views

How can I delete dangling paths after merging features

In my previous question I've asked how to can I merge different polygons while converting to GeoJSON and TopoJSON. After a day of researching I've realized that, rather trying to do it command line, ...
0
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1answer
606 views

How to read the attribute values using pyQgis?

What is the way to get the information contained in the attribute table, say in column 2, row 2 using pyQgis?
0
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1answer
2k views

How to convert a regular point grid to raster? [duplicate]

Possible Duplicate: How to convert a point grid to a raster? I´d like to convert a regular grid (25 meter) of points (XYZ) to a raster. I have tried the GRASS-tool r.in.xyz but I always get ...