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

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3
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1answer
343 views

SAGA tool 'Relative Heights and Slope Positions' - What do results tell me?

I am currently trying to get in morphometry, using the SRTM 30m DEM. I was recommended to test the SAGA mudule 'Relative Heights and Slope Positions' ...
1
vote
1answer
141 views

Ranking Elevation using QGIS?

Can QGIS automatically find the lowest land-point in a country and when you would like to, find the second lowest, third lowest land-point and so on? And on that same coin, a software that could find ...
1
vote
1answer
168 views

How to link a pdf file to a specific feature with QGIS? [duplicate]

I'm trying to link a pdf to a parcel (see image: http://imgur.com/RbauB3v) where you click on one parcel and a specific pdf comes up and if you click on another then a different pdf comes up. I've ...
2
votes
0answers
52 views

What does “Information [18]: Select at least one signature” in the semi automatic classification plugin mean?

I am using the semi automatic classification plug in to classify vegetation and water in a satellite image. I create training shp and signature list. When i hit "classification preview" it gives me ...
0
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0answers
20 views

Allocation of data by Voronois to admin units according to area in QGIS? [duplicate]

In QGIS, I need to assign values from Voronoi cells into admin 2 units (e.g., counties) with a weighted average according to the amount of territory of each county covered by the cell. So, for ...
0
votes
2answers
74 views

Spatial join geotagged images to preexisting point shapefile?

I have a layer of geotagged images (points with jpg thumbnail attachment), and another layer of different points (shapefile with various attributes). I would like to perform a spatial operation in ...
0
votes
1answer
28 views

Error during building an application c++ using api qgis 2.8

I have an apllication that need an object the object type is QgsSymbolV2 but i cannot do that : QgsSymbolV2 * lSymbol = new QgsSymbolV2(); because in the class qgssymbolv2 there is no constructor ...
2
votes
0answers
64 views

QGIS: distance matrix different outputs

In one of my plugins I would like to use the distance geoprocessing algorithm. When running this algorithm from the menu Vector->Analysis Tools->Distance Matrix I get a different output than running ...
0
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0answers
87 views

Problem with calculating slope in QGIS

Ive downloaded DEM form earthexplorer. But after calculating slope I only have blac img. with same value in min. and max. When calculating aspect or relief, DEM works correctly. Have you met with ...
2
votes
0answers
101 views

Data Upload Error for QGIS Cloud

I'm just taking a stab at QGIS Cloud to investigate it for a potential client, and I am pleased with the functionality of the web-viewer based on the sample maps. Although I cannot upload my own data. ...
1
vote
1answer
86 views

Efficiently Calculating Farthest Point from Origin

I'm trying to find a clever/efficient way to calculate the the farthest point from an origin, given a list of lat,lng points. For example, if trying to find the closest point from an origin I could ...
2
votes
2answers
304 views

How to create a zoomed in portion of a map in print composer?

I posted a question yesterday about troubles I was having with labeling (which are still plaguing me), but it hit me today that it would probably be easier for me to just create zoomed in sections of ...
4
votes
1answer
112 views

Point Coordinates Conversion with unknown system

I've been using QGis for few weeks now. Although this site always came very helpful, I can't find solution to my recent problem: I have few points, and know their coordinates in "WGS-84" and "ISN-93" ...
1
vote
0answers
42 views

Replacing white or black by alpha channel in raster in QGIS 2.8

I'd like to replace black or white in black and white raster in QGIS 2.8. I perceived that in some other raster where "nan" value automatically occurred and only white or black is being displayed.
3
votes
1answer
100 views

OpenLayers Plugin - Opencyclemap does not display correctly

It happened on version 2.6 and I was told it was my version that was the trouble, so I reverted to 2.2. The odd thing is, that it will usually work fine the first time I open the map, but it seems ...
1
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0answers
16 views

where are old function of qgssymbol

in the new version of qgis 2.8, in the c++ API and in the class QgsSymbolV2, a lot of function has been deleted, by exemple setfillcolor, setcustomtexture, setnamedpoint, setpointsize i would like to ...
2
votes
0answers
55 views

Setting constant input layer in QGIS modeler?

I have a model in QGIS where there are two vector layers that remain the same everytime I execute a model. Is there a way that I can configure my model so that these layers don't require the user to ...
1
vote
1answer
326 views

QGIS forms: How to limit available values in a dropdown field according to value selected in a previous field

I'm building a rather complex entry form for the layer stored in a PostGIS database. I have a following usage scenario: On several occasions i have dropdown fields which let user select a type of ...
3
votes
1answer
130 views

Problem with distance in QGIS

I start a new project with base on OpenLayers plugin but if I check the distance on QGIS with distance tool (I choose a straight road) I view 5.466m on QGIS and 4.300m on google (by walking). How is ...
2
votes
0answers
161 views

How to change the symbology of selected features in QGIS

In QGIS selected features are normally highlighted in a different color to draw user’s attention on the selection. The default color can be changed programmatically. As a nice to have my standalone ...
1
vote
0answers
61 views

calculate Z~F from polygon and raster

I have a polygon shapefile and raster layer. How I can calculate the elevation and area (Z~F) relationship for each polygon by using QGIS or ArcMap?
1
vote
0answers
22 views

Creating an Action using the Value column in Value Relation widget

I want to create an Action that would use the attributes (such as report_id and county) of a site_investigation_report feature to generate a file path to a PDF report. The county attribute uses the ...
0
votes
0answers
46 views

I am clipping my data points but the clipped layer is empty

I am new to QGIS and using QGIS 2.8.2. I have some points data of a whole town and I want to clip a specific region of data from it using a polygon layer. I am clipping my data points but the ...
4
votes
1answer
202 views

Raster to vector (polygons) with generalisation

I have created rasters showing different types of vegetation (bushes, trees, open land) with help from lidar data. Now I'm looking for a method to turn these images into polygons. I'm using a Mac ...
1
vote
0answers
54 views

New Issue with Open Layers Plugin Google Satellite - low res?

Recently I've noticed this issue with the open layers plugin google satellite layer where the imagery is dark and of a lower-resolution than it used to be. I frequently use this imagery with ...
10
votes
2answers
300 views

How to create dynamic leader lines?

I'm trying to create dynamic leader lines by using a PostGIS view in addition to the QGIS „Move Label“ tool. CREATE VIEW leader_line AS SELECT gid, ST_MakeLine(geom, ...
2
votes
1answer
66 views

Get nearest node following segment

I am trying to get the nearest node from a point(Id 1) . The coordinates (lat/long) are input by an user . I am using some functions like pgr_nearest_node() or get_nearest_node() from get_nearest_node ...
2
votes
1answer
57 views

QGIS: Labels shifting to different locations after I save from the attribute table

I just started working with QGIS, and I'm having a problem with my labels. I have figured out how to manually move labels for the points on my map (thanks to this forum!)--I have edited the attribute ...
1
vote
0answers
242 views

Removing pseudo-nodes using QGIS Sextante plugin?

I have a road network (vector) that i'm interested in carrying out some space syntax analysis on. Predictably my GIS data is in a pretty terrible state. For example, there are a bunch of roads on the ...
2
votes
1answer
283 views

QGIS: raster image georeference and overlay

I've created a grid and points in QGIS which I used to survey. Using a test image at the moment and I'm trying to fit this image as an overlay within a boundary. When I insert the image it has a white ...
2
votes
2answers
154 views

Can the QuickOSM QGIS plugin be used with Overpass QL (rather than xml)?

The QuickOSM plugin for QGIS can support users with the generation of new Overpass queries (for beginners on Overpass like me). It does this using the xml query language. I'd like to also be able to ...
0
votes
0answers
23 views

QGIS: “Attribute index out of bounds” error when hiding fields and using Actions

I have a long table with autoincrementing fields that the user doesn't need to see. I changed them to "hidden" through the field attribute editor. The problem is that I'm also using Actions (a ...
1
vote
1answer
57 views

Extracting regional data from vector file in QGIS

In QGIS, I have a random points data (coordinates) with assign values I have plotted it in QGIS with CSV file and now I want to extract the specific region data. How would I do this? Please guide me.
2
votes
1answer
63 views

QGIS: regular points tool numbering

I've made a regular grid and regular points for a grid, I want to set this inside of a boundary so I have deleted the points outside the boundary. However, when I do this the ID still shows up ...
1
vote
0answers
31 views

problem when building a code under qgis 2.8 c++ api

i have this code QgsUniqueValueRenderer *lRenderer = (QgsUniqueValueRenderer *)pLayer->renderer(); QMap<QString, QgsSymbol*> lSymbolMap = lRenderer->symbolMap(); QgsSymbol *lSymbol = ...
1
vote
0answers
126 views

Cannot select linesegment in QGIS

Drawing a baseline in an attempt to make a grid. Have managed to draw baseline but cannot select using cad tools "select one linesegment" tool. Worked previously and I'm not aware that I'm doing ...
2
votes
2answers
101 views

Rotation field is missing in rule-based renderer in QGIS 2.6

I am trying to do rotation of point symbols in QGIS. I am working with rule-based renderer. In other types of classification there is a button advanced (for example in categorized renderer), where I ...
1
vote
1answer
64 views

How to convert/export a large number of attribute's information shapefiles to txt/csv format using a python script

I'm using the 2.8.1 Wien QGIS version. I have a large number (more than 5000) of shapefiles that I want to convert to a csv or txt files to extract, to tables, the atributte information. The ...
1
vote
3answers
140 views

What's the parameters of heatmap formula on QGIS?

I want to calculate the values by hand to know which parameters effect the result in the image, but i couldn't able to do that because i didn't understand it. I tried with 500 mt and 1000 mt radius ...
1
vote
0answers
35 views

Clip only works on some areas, and not on others, despite being from the same dataset

I have a shapefile of provinces (nxprovincias), and another shapefile of small, disconnected areas ("protected areas") that overlaps with the provinces. I want to easily calculate the total area of ...
3
votes
0answers
68 views

Printing a 1" scale from 2.8.2 Print Composer

I'm working on a small-scale site survey in qGIS, and for engineering purposes I need to print physical copies of the map that can be used with an engineering ruler. Basically, I need a way to print ...
3
votes
2answers
322 views

Inverted shading with polygons in QGIS 2.8

Is there a way to modify the style of a poygon .shp file so that everything except the polygon is rendered as shaded? EDIT: see these images if you have trouble understanding. I am going for the ...
1
vote
0answers
63 views

Problem running intersect vector processing with line shp file and polygon shape file

I have been trying to run intersect on two shp files, one is line, the other is polygon. Although processing appears to take place and a new shp file is created and added, nothing is visible. I have ...
1
vote
1answer
42 views

How to get the upstream average of a raster data layer that falls into a river network?

I have a raster layer of a network of rivers and a raster layer of data I want to extract. For each pixel of the rivers, I need to know the upstream average of the data layer that falls into the ...
3
votes
3answers
54 views

Why does Georef'd image show as a large black area

Using QGIS2.4.0 I just added 2 maps to an existing project. Both are scanned images of pre-1800 plans. One is a jpg file, I georef'd and added to QGIS no problem and plan displays in the project. I ...
0
votes
0answers
68 views

Snapping feature nodes doesn't work after feature creation (filter involved)

I've experienced a strange behaviour during editing mode: I have set a filter to 2 features (polygons), part of on of my PostGIS layers: "name"='A' OR "name"='B' After that I have created a new ...
1
vote
0answers
40 views

Batch processing ( offset of font marker) in QGIS

I have a group of layers with type linestring. Every line consists of simple line and marker line (font marker). I have a batch file(csv) with offsets of font markers. Do you know if there is any ...
1
vote
1answer
212 views

Spatial Query: The query from “LayerName” using “FID” in field not possible

In QGIS Wien, I am performing a spatial query with two layers (points and buffer areas) and receive the following error when creating a new layer with intersecting features: The query from "LayerName" ...
1
vote
1answer
102 views

QGIS for geophysical surveying?

I need to make 30x30 and 20x20 grid layouts with co-ordinate points in the corners. These points then need to be relayed to a GPS to be able to set the grids out in person and then survey them. The ...
1
vote
1answer
73 views

Visualising Multiple Routes from pgrouting in QGIS

I am able to Visualise the Single Route from Source A to Target B by the following code in QGIS SQL "id" in ( SELECT id2 as id FROM pgr_dijkstra( 'SELECT id, source, target, cost FROM ways', ...