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

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0
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1answer
12 views

how to generate NDVI with multi channel images?

I have a 6 channel proprietary camera and I need to create a NDVI map. I created a map from each band, so now I have 6 files each one on a different band width. How can I proceed now? I am using QGIS ...
4
votes
1answer
319 views

NAD83 and NAD83 State Plane

I'm struggling with a projection question. I have some data in California State Plane and am trying to align a NED with NAD83. I thought these would just natively align, but they don't seem to ...
0
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0answers
8 views

Finding census block with highest pop. value within the census tract

In QGIS, I'm trying to plot a centroid of only the census block with the highest population within each census tract. So there should only be one point per tract- that of the block with the greatest ...
0
votes
1answer
227 views

Z value (height,altitude) from 3D multipoint shapefile in QGIS

Is there a way to get Z value/height/altitude from 3D multipoint shapefile in QGIS? All I found is way through SpatiaLite or PostGIS as explained here: ...
1
vote
1answer
26 views

QGIS Affine Transformation Parameters

I try to use the qgsAffine plugin to do the transformation. But no idea in its usage. Anyone can post an example. Many thanks!! How to find the transformation parameters? I found some posts suggest ...
2
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0answers
33 views

Finding and using data on population density files

I'm new to GIS and been trying to figure so many things out on my own by using QGIS. Now on to my question. I'm attempting to replicate this map for the state of Nevada: ...
1
vote
2answers
347 views

Can I prevent QGIS raster clipper from changing output cell/pixel size?

I have performed a DEM extraction using the clipper tool in QGIS 1.9.0 Master, using a mask layer, the original resolution of the DEM is 20x20 but in the resultant DEM the new resolution is ...
1
vote
1answer
48 views

Create floorplan KML file in QGIS?

I import a building floor plan from DXF format to QGIS. When I export it to KML format and then import it in Google Earth, how can I put the floor plan to my desire building location? MY CRS is WSG84 ...
1
vote
3answers
112 views

QGIS OpenLayers Google Maps not zooming

Google Satellite will not zoom. Although the scale changes as I zoom, as the map is re-rendered, it zooms out to its maximum extent every time. This first happened in the latter part of November ...
1
vote
1answer
741 views

Having trouble connecting QGIS with postgres database with postgis extension

I am working on Ubuntu Precise with postgresql version 9.3 and postgis 2.0. After initially starting my postgres database and eventually getting permission errors that would prevent postgres from ...
5
votes
3answers
1k views

Producing singlepart featureclass with unique IDs for each spatially non-connected polygon?

What is the best method to convert a singlepart shapefile (i.e. one record that contains several non-connected polygons) into a mutlipart shapefile? For clarification the original question asked how ...
3
votes
1answer
168 views

Problem operating LAStools in QGIS 2.6.1

I have a problem with LAStools in QGIS 2.6.1. I have never used QGIS to process LiDAR data before. I downloaded LAStools yesterday from the rapidlasso GmbH website. I unzipped the “lastools.zip” ...
2
votes
1answer
95 views

Layer with custom UI not working properly

I have a problem with QGIS 2.4 when introducing layers with a custom UI. More precisely, widgets such as CheckBoxes are not recognised as such (appear as Text Edit in Attributes) and the corresponding ...
2
votes
1answer
202 views

How to make labels' size relative to the map in QGIS1.8?

I want to make my labels' size changed automatically with the scale of the map,so in the menu of "Layer labeling settings",I set the Text size" in map Unit".However,the labels in the selected layer ...
0
votes
1answer
254 views

visualize bounding box to a polygon

I try to make plugin in QGIS that compare 2 bounding box data, ex: (-32.61442167739459, -32.017601026186576, 13.015663782506067, 13.428145228091406) and (-38.6102467739459, -38.017601026186576, ...
2
votes
2answers
82 views

Zebra grid is not displayed in map composer

in Qgis 2.6, in Map composer, while selecting grid frame style as Zebra, it does not works. Also while drawing coordinates points as exterior in map convas, it is not displayed. Actually I am facing ...
4
votes
1answer
336 views

How to add a layer group using pyQGIS?

Good morning, I would like to know how I can create a new group in the layer manager using python code, someone could help me?
0
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0answers
16 views

Error generating using SAGA

I am trying to generate a Slope Curvature Raster in Saga, but i am always getting the same error (images with the errors below). And when i use GRASS it generates with no problems. What could be the ...
0
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0answers
50 views

How to fix “Unable to load GdalTools plugin. The required ”osgeo [python-gdal]“ module is missing.”

When I start QGIS, it display error message: Unable to load GdalTools plugin. The required "osgeo [python-gdal]" module is missing. Install it and try again. Couldn't load plugin 'processing' from ...
1
vote
1answer
73 views

QGIS does not update data in Geoserver WFS-T

I am trying to edit a WFS from geoserver (using PostGIS data) within QGIS. This is the request as recorded by Fiddler <Transaction xmlns="http://www.opengis.net/wfs" ...
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0answers
51 views

Issues with QGIS WFS editing/PostGIS rendering

I want to be able to view and edit spatial data within a postgis database. I have tried using a WFS with Geoserver - but constantly get 'Empty Response' error and the Network log says the request ...
1
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0answers
60 views

QGIS Freehand editing plug-in: blocked attribute table

I can't save object after drawing by Freehand editing plug-in. I suppose it will be connected with creating some (special) column in the table. Could anyone suggest a solution?
1
vote
1answer
102 views

Smoothly interpolating Polygons from set of coordinates?

I'm still quite new to QGIS and I'm using it to display and analyze my soil data. I have point information on the distribution of the soils in a specific area and I need to create a soil map from ...
-3
votes
0answers
20 views

c++ qgisvector layer is not Valid [on hold]

#include <QtCore> #include <QApplication> #include <QWidget> #include <qgsapplication.h> #include <QMainWindow> #include <qgsmapcanvas.h> #include ...
1
vote
1answer
25 views

Route and distance measuring

I'm looking for a plugin that can make a route from given GPS points and then calculate the distance of this route. I'm going to create GPS points and import it to Qgis as a GPX file. I know I can ...
1
vote
1answer
667 views

Import SketchUp created KML contour lines model to QGIS

There's a neat trick to create contour lines based on the GE 3D terrain using Sketch-Up. The resulting KML however is a model I have looked at ways of importing KML layers to QGIS, like it was ...
1
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0answers
23 views

how to automatically update column based on the second layer, trigger, postgreSQL

I am newbie in postgreSQL. I have 2 tables, observation and landcover, i want to create a trigger which would allowed to update the column observation.land based on the spatial information according ...
2
votes
0answers
18 views

Help getting a Mathematical Representation within a Layer's Attribute Table

I'v been playing around with Vector Coding and was wondering if there was any Plugins out there that might let me represent Vectors within a layer as it's Mathematic attributes in the Layer's ...
2
votes
1answer
166 views

QGIS Python Labelling [on hold]

i want to label a point layer with those values exceeding a set of variables attribute table as follows 'loc field'(text),'a'(float),'b'(float),'c'(float) variables as follows vara = 5, varb = 3, ...
0
votes
1answer
200 views

QGIS 2.0 Howto copy raster data from a QgsRasterDataProvider to an OpenCV matrix

I'm hacking the half day arround a problem and that I' thought it was simple one. I'm using C++ (QtCreator) QGIS 2.0 und openCV2 on an 64 bit Workstation runnig Debian Wheezy. The Application I try to ...
10
votes
2answers
604 views

How to link dataframes in ArcGIS or QGIS?

The below image shows a layout in ArcGIS 10.1 with four dataframes. Each dataframe is of the same geographic area, although they are different images. For example, the top left image is a 1989 DOQ, ...
1
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1answer
251 views

query / filter on attribute tables with external tables joined

i tried to do some queries on joiend table fields ... i've got/found some answers concerning version 1.8 - which result in "use select + export to create a combined dataset" so i just did some tests ...
4
votes
2answers
449 views

Load and display a layer using PYQGIS

I'm having a go at using pyqgis from within the QGIS python console to load a layer from SQL Server and display it. I feel like I'm part way there but I'm having a real issue getting the layer to ...
3
votes
3answers
279 views

How to calculate peaks in a DEM

How could I extract all peaks from a DEM (large mountainous area)? Peak means something like: a pixel which is sourrounded by other pixels with smaler elevation numbers in a area arround the ...
-1
votes
0answers
29 views

Split polygon based on line qgis [on hold]

I would like to split polygons based on intersection of a polyline. How can i do this with python in QGIS? Thanks
-1
votes
2answers
50 views

File or personal database in qgis?

is there any database ? I use ArcMap with file geodatabase. But now, i have make project in qgis and i dont know, how to create database.
1
vote
2answers
133 views

render geotiff tiles as a map layer

i have the following problem: i have downloaded tiff files with gMapMaker and transformed them to GeoTiff using the associated .map files in QGIS. now i want to render these GeoTiff files to use them ...
1
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0answers
31 views

What am I doing wrong with QGIS v.clean?

I thought I understood how the GRASS v.clean tool worked in QGIS (in 2.6.1 Brighton) but I keep getting unexpected results and errors with a polygon ShapeFile. I've run the QGIS TopologyChecker with ...
1
vote
2answers
20 views

QComboBox nested within a Qmenu?

Is it possible to nest a QComboBox inside of a Qmenu within QGIS? Below is my current code and an associated screenshot with the unexpected results. (orange = current incorrect placement, green = ...
1
vote
1answer
41 views

How to split a text attribute by characters in QGIS 2.6.0

Is it possible to make a new column, for example named "Test" and store the first part of the column "Name" split by -? See below how it should look like:
1
vote
0answers
31 views

Assessing Flood Hazard Risk Zones using DEM

My Question: What is the best effective way to quickly estimate flood hazard risk areas using DEM data? Ideally I am looking for guidance to move forward and perform this process over large areas ...
2
votes
1answer
35 views

Models -> [Example Models] -> Contour lines from points: on MAC

I'm running QGIS2.6 on a Mac and can't seem to locate the "Contour Lines from Points" Example Model. Any help would be appreciated. SAGA is installed.
22
votes
5answers
2k views

How to generalize a polygon file and maintain topology in QGIS?

I have a polygon Shapefile, which I need to generalize. How can I generalize the poligons and ensure that there are no topological errors like "slivers". I already tried: Vector -> Geometry Tools ...
1
vote
0answers
16 views

Syntax to use when entering geographic data into geography columns via SQLSERVER Management Studio

I am starting to learn about spatially aware databases. I have QGIS 2.61 and SQLserver express 2012. I can set up a table using the SQL Server Management studio GUI and insert a geography column. ...
3
votes
0answers
28 views

Merge Raster Layer Specific Order in Graphic Modeler

I'm using the Graphic Modeler/Processing Modeler to automate a process. The last step in this process is Merging three different Raster Layers. I'm using the "Merge Raster Layers" from Saga 2.0.8. ...
2
votes
1answer
32 views

QGIS has an automatic way of finding the LS factor?

I wonder if is possible to calculate LS (soil erosion) factor automatically in QGIS? Or at least a way to calculate the length slope?
1
vote
1answer
17 views

QGIS plugin select and edit features performance issues

I wrote a plugin for selecting and instant updating the value of the selected feature in the attribute table. I tested with a big shapefile and to select and edit 5 features takes ~5 seconds. Which ...
3
votes
1answer
30 views

Change no-data pixel value in raster: QGIS 2.6

I want to change the value in all pixels that are currently 0 to 800 in QGIS 2.6.1. 0 is listed as the no-data value in Properties > Transparency. I have unchecked the No Data Value box there. Then I ...
1
vote
1answer
44 views

What is a memory vector layer in QGIS?

What is a memory vector layer and how does it relate to the vector layer? Background info: I have a volunteer working with my organization, because of financial reasons we have him using QGIS. He ...
8
votes
3answers
140 views

Calculating all distances from single points to multiple polygons

I have two layers: a point layer defining properties (95 objects), and a polygon layer defining plots of land associated with the properties (211 objects). Each point relates to one or more polygons. ...