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3
votes
3answers
433 views

How to make a local copy of a large WFS dataset?

We are writing a application in which a part of the job is to fetch a relatively large (>10000 features) and often updated dataset from a WFS server, store a local copy, and do geospatial analyses on ...
1
vote
1answer
1k views

How to compute distances between points and polygon borders?

I have point data and polygon in vector format. For each point, I want the distance from the point to the border of the polygon. However, if the point is inside the polygon, I want negative distance ...
0
votes
0answers
44 views

Georeference a computed tomography image without changing its proportions in QGIS

I have several images obtained from a Micro computed tomography (mCT). The scanned elements are human teeth. In a particular mCT slice, I have introduced a cartesian plot with its X and Y axis. The (...
2
votes
1answer
173 views

How to get mean geographic direction of a polygon in QGIS?

I have a raster height model and would like to calculate the horizontal geographic direction (north, east, etc. - orientation) of each cell, then calculate then the mean value of all these cells in ...
3
votes
4answers
165 views

Calculate minimum area where x% of raster value total is concentrated within polygons

I have a raster layer (chlorophyll concentration) and a layer of non-overlapping polygons (regions of the ocean). For each polygon, I'd like to calculate the area where the majority of chlorophyll is ...
3
votes
2answers
166 views

Raster Caculator Qgis 2.6 v/s Gdal_calc.py by Terminal

I need calculated monthly mean of Snowcover data by MODIS product, and then modify this script gdal_calc.py in this section # create alphabetic list for storing input layers AlphaList=["A","B","C","...
1
vote
1answer
369 views

gHydraulic plugin for QGIS 2.8 make EPANET Model Type Error

I've set up my water network layers to create an EPANET model using the gHydraulics plugin for QGIS 2.8: pipes, junctions, and a reservoir. The pipes have unique IDs, with their corresponding ...
2
votes
1answer
486 views

Why does “Join attributes by location” fail to compute sums when used in a model?

If I use "Join attributes by location" from the menu it works fine but if I'm using it within the Processing modeler it's not working. I want to sum up previously selected records having a field area ...
2
votes
2answers
658 views

Create a script to add delimited text layer in QGIS

I'm trying to use QgsVectorLayer() function to add delimited text layer in QGIS. So I have a txt file (T_1999_1_2.txt) in path: "D:\PATRICIA\DOCUMENTOS\ESTACOES METEOROLOGICAS\DADOS METEOROLOGICOS\T" ...
1
vote
1answer
114 views

QgsComposerMap does not fit extent

Please help me to fit the map extent into de qgscomposermap size. printable_layers = QgsMapLayerRegistry.instance().mapLayers().values() printable_layers_ids = [] ...
0
votes
1answer
86 views

QGIS how to delete virtual fields?

I can't find the option to delete a virtual field on a layer, not even in the table manager plugin. Where is that option?
2
votes
1answer
402 views

Qt/C++ Hello World application with QGIS not compiled: qgsconfig.h not found

I am a Qt/C++ developer. I have to create a GUI application (Qt/C++) with GIS maps. I'm trying to do that using QGIS. I'm working in Linux Ubuntu with Qt Creator 2.4.1 (based on Qt 4.8.0). I did the ...
1
vote
0answers
59 views

Creating a single layer of polygons from a point layer

I have a csv file of lats and lons for points that represent the vertices of parcels of land. I want to create a polygon for each set of specific points within the csv and then create one unified ...
0
votes
0answers
46 views

Can I style basemaps provided by OpenLayers in QGIS?

I absolutely love openlayers plugin, and it's been great help. It'd be greater if I can style the base maps such as disabling labels, changing opacity etc, which are all possible when working with ...
3
votes
0answers
158 views

Enable LWGEOM for OGR tools (QGIS 2.8)

I am doing some scripted operations on a Spatialite DB using OGRINFO, OGR2OGR etc. in the QGIS 2.8 OSGEO4W shell. Unfortunately, LWGEOM functions such as ST_Split() are unavailable and lwgeom_version(...
1
vote
1answer
221 views

How to convert multiple vector layers to georeferenced rasters using QGIS?

I have Openstreetmap background loaded in QGIS - currently from Spatialite, but no problem to get shapefiles. I need to convert the loaded map to one big raster or could also by more smaller ones, ...
1
vote
1answer
446 views

QGIS / Python: Fill new field with values based on other fields and lookup table

I am trying to use Python for QGIS to add values to new fields in an attribute table based on existing fields and values in a lookup table. Attribute table I wish to modify (with example rows): farm ...
1
vote
1answer
27 views

qgis script in external IDE fails [closed]

I'm new to Qgis. I have a script that runs successfully inside the Qgis editor, but it fails outside. It returns the alghelp, but fails on running the actual tool so it seems I have the external IDE ...
3
votes
2answers
220 views

Merging linestrings in QGIS using PostgreSQL and PostGIS

I've to merge all linestrings from a PostgreSQL table "river" where not more than two start-/endpoints are overlapping. In the illustration below I use a "M" to mark all linestrings that needs to be ...
0
votes
0answers
67 views

Is it possible to use d.nviz in QGIS 2.8.2?

I read that this algorithm belongs to GRASS 7 only but GRASS 7 doesn't work in QGIS (Missing dependencies). How do I do that? By the way I want a raster animation with time. And d.nviz can help with, ...
2
votes
2answers
93 views

How can I check if all boundaries of a polygon coincides with one or more of a set of lines

I have a polygon shapefile, and theoretically, all features in the shape are bounded by the union of some lines in another shapefile. Is there any way to confirm if this is true? I'm using QGis, FME ...
1
vote
2answers
364 views

Shortest Path Matrix with QGIS/GRASS

I signed up just a minute ago, because I am working on my Master's thesis and could not find a working solution for the following problem: I am analyzing Germany's high voltage electricity grid. I ...
1
vote
0answers
160 views

How to remove a QgsMapCanvasLayer from QgsMapCanvas with PyQGIS || C++?

I try to find a way to remove a QgsMapCanvasLayer from the QgsMapCanvas. At the moment I only can delete the MapLayer from the QgsMapLayerRegistry with: QgsMapRegistry::instance()->...
2
votes
2answers
258 views

How to display multiple attributes in a QGIS Composer legend?

I have a polygon layer which has a number attribute and a text attribute. When I make a legend in the composer, it automatically chooses the number to display while I would like to have both the ...
0
votes
1answer
59 views

How to get unique feature count from a field w.r.t another field using ogrinfo?

We have some 40 folders which has two - three tab files in each folder. Table structure will be the same for all the tab files. What i would like to extract is Feature Count, LineNo (will be 0,1,2,3,...
2
votes
0answers
48 views

Expand data set by interpolation

I have a data set that is classified into 7 landcover classes. I've been asked to expand this data set to a new boundary. My question is How can I interpolate my existing data out to meet the new ...
0
votes
0answers
119 views

Calculating driving distances from a number of post codes to a number of services using QGIS

I am hoping to calculate the driving distance from a large number of post codes to their nearest service. I have used the RoadGraph plugin but this only calculates the distance and time from one ...
0
votes
1answer
94 views

.mdb is not a valid layer and can not be added to the map

I know this question has been asked quite a few times before but I couldn't find an answer that suited my situation at all. So this is what happens. Currently, I am using ArcGIS to map the sewer ...
0
votes
1answer
186 views

GeoServer namespace URI causing invalid WFS transaction requests

Is there any naming conventions with GeoServer's namespace URI/settings that need to be changed to allow their proper use? I have a WFS-T that is being edited in QGIS - after a lot of issues getting '...
1
vote
1answer
69 views

How to calculate the area of a raster within a polygon which is greater than a specified value?

I'm using QGIS (2.8.1-Wien) and I have a raster layer showing chlorophyll concentrations in the ocean. I have also defined number of regions of the ocean using polygons. What I'd like to calculate for ...
1
vote
1answer
936 views

Area is calculating wrong using $area in field calculator (QGIS 2.8.1-Wien)

There is a similar question posted, but the solution to it seems to be that polygons were multipart: Wrong $area from field calculator (QGIS) In my case, all polygons are singlepart. I have several ...
2
votes
1answer
395 views

NULL to 0 values in vactor attribute table in QGIS [duplicate]

I need to converte NULL values to 0 values with the overall goal of sum up two columns in attribute table in QGIS. Since one of these colums has NULL values, the new column with the sum also appears ...
1
vote
0answers
53 views

How to create a map series of different rasters (same location, same legend)?

We have hundreds of raster images at the same location (same dimensions, pixel size, projection, etc.). We would like to display each one in its own map using the same legend with the same vector ...
1
vote
2answers
157 views

How to add an image to canvas?

I am trying to make a QGIS plugin using Python. Right now I need way add an image to canvas but I don't want that image to be a new layer in qgis project. Is there a way to do it? Now I have: self....
1
vote
2answers
1k views

How to convert features of layer from POLYGON to MULTIPOLYGON?

How can I convert features of a layer from POLYGON to MULTIPOLYGON? I know how to do that using the postgis function ST_Multi but how could I do to same thing for a layer in QGIS?
6
votes
2answers
153 views

Complex Shapefile Compression Advice

I'm looking for some advice on how I can simplify this very detailed shapefile to ultimately be used for the web (as topojson) as a interactive heatmap. It was originally created from a raster file (...
0
votes
1answer
98 views

Snapping points to Polygon using QGIS?

Can QGIS automatically snap points to a polygon in a layer? From that can the points then be put into a text delimited file in sequencial order?
2
votes
0answers
106 views

Digitizing complex archaeological scenarios in various levels

I don't know if this issue has already been answered, but I can't get my head around it. I used to do this in Illustrator, and there it was simply a matter of clicking "bring forward/bring back" etc. ...
1
vote
2answers
124 views

How to remove outlying islands from a DEM raster?

I have a raster image that looks like this (see below) How do I remove the outlying islands and keep only the central main island in the image. Is it a geoprocessing clip function? I am using QGIS ...
0
votes
1answer
151 views

Getting the nearest point and applying attribute filter using Distance Matrix in QGIS

I have two point layers, one with 233 row, other with 1531. For every point in layer 1, I would like to get the closest point from layer 2, (ok simple enough, but here's a trick) that has the value of ...
2
votes
2answers
1k views

How do I embed the a Leaflet map into my web page, using QGIS2Leaf?

I am generally new to web developement, and web gis for that matter, but I want to embed a leaflet map that I made in QGIS using the QGIS2leaf pluggin, into the html of my webpage, but am having ...
1
vote
3answers
189 views

Spatial distribution of an invasive specie across a landscape : what analysis?

I'm studying the spatial distribution of an invasive specie introduced in a natural area. This plant, that thrives in sunlight, grows in thickets (patches). The population of my study site (10x10 km) ...
2
votes
1answer
209 views

How to interpolate line Z from sparse attribute values

I have a series of end-to-end connected 3d lines which I'd like to add elevation values for all vertices on the lines which are currently null or 0. How to accomplish this? In the following image ...
0
votes
1answer
157 views

How to create loops using processing algorithm in python console from QGIS

I'm new with python programming and I need some help for my case. I want to use inverse distance weighted function to interpolate precipitation values using values from 78 weather stations. so I ...
1
vote
1answer
57 views

Is it possible to run Points2one in batch mode?

Is it possible to run Points2one in batch mode (using Qgis 2.8.1 on Unbuntu 12.04)? Basically I have 85 separate point layers and I want to create polygons using Points2one for each layer.
0
votes
1answer
221 views

How to suppress advanced digitizing tool window

I'm using QGis for years but suddenly I stuck with something that I'm sure it's an easy fix. Every time I start to create a new feature, the Advanced Digitizing tool window pops up. Do you know how to ...
2
votes
0answers
66 views

Sophisticated generation and calculation of Vector entities from Raster Data?

The first image below is shown a raster wish represents the altitude value. I created this raster by applying this process, bu using this process we can manually select an upper and lower area (so 2 ...
4
votes
1answer
232 views

When saving a .qgs file in QGIS, another appears. Is this a backup?

When saving a project file (.qgs), which when executed is automatically loaded with qgis.bat, there's another .qgs file which appears in the same directory of the original project file, although this ...
0
votes
1answer
152 views

Debug QGIS crash on Windows 7 - how?

I'm developing a QGIS plugin, and under certain circumstances, it causes QGIS itself to crash. How can I debug this, given that I am on Windows 7? I've tried using the QGIS nightly dev build (which ...
1
vote
0answers
136 views

QGIS 2.8 (openSuse 13.1) pdf export with print composer not working

I'm using QGIS 2.8 with a openSuse 13.1 system. If I try to export a map (with openlayers-plugin active) with 120 dpi it works fine, but if I change the dpi setting to something higher (like 130 dpi) ...