Tagged Questions

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

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0answers
43 views

How to compute the ls factor equation for USLE model in qgis grass r.mapcalc

To compute the LS factor for the USLE model, the following equation easily works in ArcGIS. How can I perform the same in QGIS under GRASS r.mapcalc? LSfator = Power (("flowaccNW") * ...
2
votes
1answer
45 views

Add XY Column in QGIS [duplicate]

Following on from a previous question of mine, where I was given coords in degree-mins, I have successfully converted them to decimal degrees, thanks for the help. I have created a CSV file from ...
0
votes
1answer
74 views

How to delete column/field in PyQGIS?

How to remove or delete column fields in a shape file using python?
4
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1answer
96 views

Pulling CSV file directly from website into QGIS?

I want to be able to automatically update my csv files in a QGIS project. My organization has an online database that can easily export csv files. These csv files are constantly updated with new ...
0
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1answer
91 views

How to perform an attribute-weighted sum of multiple polyline features from a single vector layer?

I have a shapefile of ~8000 polyline vector features representing traffic journeys on road routes. Each has an attribute representing volume of traffic for that journey. The routes are all generated ...
1
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1answer
52 views

QGIS Filters and Queries

In QGIS is there a way to filter a layer using the Query Builder to show all values which include a particular phrase. For example I have a list of organisations and I want to filter all those which ...
2
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0answers
63 views

Lat Long to Useable values in QGIS

I am using both QGIS 1.8 and 2.0. So either is helpful. A client has given me locations of trial pits but i cannot load them into QGIS no matter how hard i try. For example, 50°24.711 North ...
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1answer
42 views

Apply new style to selected features in QGis

Let's assume that I have selected some features in QGis. Now all the features in that vector layer already has some style applied to it. Now, I want to apply some new style to the selected features. ...
3
votes
1answer
36 views

How to select more than one feature using values?

What should I do if I want to select more than one feature using values ? For selecting a single feature, I enter an expression like this which works: "LINK" = 28 Assume LINK as a field in the ...
1
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1answer
62 views

How to increase the resolution of a 3D image in QGIS GRASS NVIZ

I'm trying to display 3D data in NVIZ within QGIS, but the result appears very low resolution in comparison to the same data in ArcScene. Any ideas as to how to improve the quality would be greatly ...
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0answers
78 views

How to convert data type from float to integer in QGIS?

Currently I am working on importing data from MSSQL to Qgis 2.4. In imported database table attributes are shown in the format of integer ( in attribute table it showing like 48.23 and 16.20 in ...
2
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0answers
55 views

Is it possible to change the default raster style of newly created rasters in QGIS?

If I do calculations on rasters with the raster calculator or other tools, the resulting rasters displayed in my canvas are always in the same default style (singleband gray, black to white...) so ...
2
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0answers
49 views

How to add a TIF raster layer programmatically?

This is my code whenever i try to load .tif image it shows layer is not valid,QgsRasterLayer always return invalid layer (I am using linux 12.04). QString myFileName = ...
2
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0answers
40 views

How to group a multiple rasters in MapServer?

I had a map files for each state (raster file) of India. Now I want group all mapfiles to show a single raster or single map file? How I can do in using qgis or any platform?.
2
votes
1answer
101 views

How to do a “fuzzy” intersection?

I have two layers that look like this: I want the intersection (or whatever the correct term may be) to look like this where the output polygons are the same as the original base layer, just with ...
0
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0answers
67 views

Merge/mosaic categorical rasters in QGIS/GDAL

I am attempting to make yearly bins of some monthly MODIS data for all of the US. The cells of the raster are defined with Julian dates indicating the date at which a burn event took place. After ...
3
votes
2answers
99 views

Use Values from Raster Statistics (e.g. sum of all cells) in Raster Calculator

I need to do calculations on raster layers which require the sum of all cells of the raster. I've used the zonal statistics tool for that but it gets a little annoying to do those extra steps (run the ...
1
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1answer
60 views

Suggestions on Imagery type for ArcGIS for Server (Without Image Extension)

I am exploring the best options to serving raster imagery on ArcGIS for server 10.2.2. As a background, I currently have roughly 200 .jp2 files of about 3mb each. All of these files are currently ...
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0answers
46 views

Developing a Slope Map of India [closed]

I am working on developing a Slope map of India (for my research), where I collected DEM from Bhuvan and tried to mosaic and then perform terrain analysis. But I am unable get the output since the ...
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2answers
75 views

Display Point Labels in QGIS

I have coordinates and points from that coordinates. so what do i need to do to show point numbers on the map? Thanks. It's my second day with QGIS
1
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1answer
66 views

How to write a (memory) layer from QGIS to PostGIS?

I am looking for an "elegant" solution to write, from a python script, a layer from qgis and into a new table of a PostGIS database. I thougth that this might be solved by QgsWriteVectorLayer, but I ...
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0answers
43 views

Is there a way to take control of the mouse pointer using python in QGIS?

i would like to take control of the mouse pointer in QGIS (for example constraining it to a given extent...) Is there any way to do that using PyQGIS ? Thanks !
0
votes
1answer
137 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: ...
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0answers
24 views

Rotate polygon preserving topology in QGIS?

Is it possible in QGIS? What I need is: 1) Rotate a polygon inside another one (bigger), obviously the polygons are not overlapped. 2) Rotate a given polygon in a topologically correct layer (like a ...
1
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1answer
75 views

mmqgis plugin not showing up in plugin dropdown menu

I have installed the plugin from the plugin dialog box, but I am unable to figure out exactly how to run the plugin.
5
votes
2answers
123 views

CRS for submission to Minnesota DOT

Does anyone have experience using QGIS to submit shape files to the Minnesota DOT (MNDOT)? I am using EPSG:26915 but got rejected due to an error in the CRS. MNDOT Specs call for "UTM coordinates, ...
2
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1answer
96 views

*Value relation* widget in QGIS

I cannot understand what the Value Relation widget of the Fields menu in QGIS actually does. For example: I have a point layer with some columns (ID, value1...) and a table (so just a dbf file) with ...
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0answers
111 views

Can QGIS open a SDF file created by HEC RAS?

I used the "export GIS data" option in HEC RAS and got a SDF file. Is it possible to open it in QGIS?
2
votes
1answer
414 views

How to install LAS tools in Processing for QGIS 2.4?

Does anyone know were the processing menu moved in QGIS 2.4? Specifically I am trying to install the Lastools box for QGIS following these instructions. ...
0
votes
1answer
62 views

Creating a new shapefile based on an existing problematic shapefile

I have a large floodplain shapefile and would like to create a new shapefile based on coverage. I'm having major problems with the original (intersections and other errors) which I've been unable to ...
0
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0answers
35 views

QGIS DEM Output cell size does not match DEM input cell size

As my first post I offer a humble apology if this is such a basic question as to make any of you cringe. I feel like I have exhausted my search skills and read through the QGIS documentation ...
2
votes
1answer
41 views

Query DEM Elevation at Point in QGIS

I'd like to be able to pull up a DEM (or create a mosaic of them) and simply query the elevation at points I click. Is this possible using QGIS?
2
votes
3answers
244 views

How can I work with very large shapefiles (~1 GB) in QGIS?

I'm performing some basic spatial analyses on a large database of traffic injuries in California between 2003 - 2011. Because the dataset is large (nearly 1 GB of points), I'd like to first cut it ...
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0answers
28 views

Will QGIS fulfill my requirements? moveable, rotatable, draggable, complex, interactive icons

I'm trying to compile a list of mapping software that will fit my requirements for a desktop application I want to build. I'm trying to build something similar to MissionPlanner: ...
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0answers
25 views

Is there a Targer-like tool for QGis?

I'm trying to make subsurface drillhole and I heard that Target (an AutoCad tool) can help me with this task but the issue is that I work with QGis.
1
vote
1answer
72 views

QGIS distance from points to nearest line

How can I get the distances from each point at a shapefile to the nearest line from another? I've tried to follow the directions from Measuring the distance between lines and points in QGIS and ...
2
votes
2answers
205 views

QGIS Raster Calculator: Need values to be set to 0 instead of no data

I have a landcover map with different values for the landuse options e.g. 190 for commercially used areas. Now I want to extract only these areas using the Raster Calculator with the expression ...
1
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0answers
35 views

Tagging polygons within larger polygons (spatial join)

another QGIS newbie here. I have a number of smaller polygons which perfectly aggregate to a larger polygon. I want to "tag" the smaller polygons with the ID of the larger polygon they make up. ...
4
votes
1answer
97 views

In which way is height information stored in a DEM?

I'm struggling with different DEM data, because I don't know how to convert the height information in meters. When I load ASTER and SRTM tifs in QGIS, it shows me the spectrum of the grayband (0 to ...
1
vote
1answer
74 views

How to batch-process attribute tables in QGIS (or GRASS)?

I'm using GRASS 6.4.3 in Linuxmint 16. I have a bash script for GRASS which I use to process almost 300 raster files. The script first imports some raster files (r.in.gdal), then does some ...
1
vote
1answer
39 views

Is there a way to define the relative position of items in print composer?

Is there any chance to make the items in print composer relative to the margins. Let's say for example the legend. I normally align it to the corner on the right bottom where the legend is 10 px away ...
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0answers
86 views

How to create a rainfall raster from rainfall contours?

I downloaded a free rainfall data from the Philippine GIS Data Clearinghouse (PhilGIS) which are vector lines. How can I extract the data points from this? I want to extract it because i will be ...
1
vote
0answers
31 views

Converting DEM data to height information in meters using QGIS? [duplicate]

I'm relatively new with QGIS and currently I'm working with ASTER and SRTM DEMs. The goal is to create vector heightcontours with labeling in meter. Can you tell me how I can convert the grayband ...
1
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0answers
51 views

How to sort a column in attribute table programmatically

Is there any way to sort ( alphabetically ) a column in the attribute table programmatically (without clicking on the column header) in QGIS ?
1
vote
0answers
45 views

Modifying properties of Attributes Table in QGIS?

In my QGIS project I'm using vector layers that require a lot of data inputting/editing. The problem is that some of the data I'm inputting varies greatly in matter of length and structure (various ...
1
vote
0answers
65 views

Creating a marker proportionally offset along a line in QGIS 2.4 when re-projecting

One of the nice new features in QGIS 2.4 is to be able to offset markers (e.g. arrow heads) along a line as part of the styling. I am trying to display a dataset of simple lines (not polylines) with ...
1
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0answers
77 views

r.stream.* commands do not work in qgis environment

I have been working for a while with some grass commands in QGIS environment (r.watershed, r.terraflow, r.thin, r.to.vect etc) with out any problem. I haven't been able to get any results at all from ...
3
votes
1answer
185 views

Wrong scale when importing dxf into QGIS

Has anyone had the problem that the scale of the shp layer converted originally from a .dxf file turns out to be wrong? (for example I draw a line of 10 meters long in AutoCAD and imported it in QGIS, ...
1
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0answers
44 views

from shape files to a database

I've previously converted simple shape files to WKT so that I can store them in RDMS that has spatial capabilities. I'm a new user to QGIS, which I'm using to browse a shape file. But now I have a ...
1
vote
0answers
38 views

Polygonize Missing Polygons

Polygonize is not capturing all of the pixels in an image that has been converted to 0s & 1s. The pics below show -original geotif -geotif recalculated to 0s & 1s -polygonize output As the ...