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1500 questions
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1 answer

GeoPackage in QGIS: what are .gpkg-shm and .gpkg-wal files?

In QGIS, if I open some GeoPackage file like mylayers.gpkg, it will create two files named mylayers.gpkg-shm and mylayers.gpkg-wal in the same folder. After I close QGIS, these files disappear. I understand that they are temporary files, but I…
Yaroslav
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22
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3 answers

Algorithm to find out points of inflection for a polyline

I am trying to find out the points of inflection , i.e. points where the curves in a line start and end. If you look at the image, the green line may be a road or a stream, and the black points are the points where the curves start and end. What…
Devdatta Tengshe
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22
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3 answers

(When) should I use a GIS-enabled database?

I am a long-time programmer, new to GIS. I am trying to get a feel for the database aspects of GIS and I understand that there are some databases which are specialized for GIS use. Basically I am trying to understand whether to use such a database…
Mawg says reinstate Monica
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22
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2 answers

Creating polygon layer from polyline layer in QGIS

Our systems expect polygon shapefiles, representing a collection of non-intersecting and geometrically valid (Multi)Polygons. Specifically, farm fields. We often receive our representations of farms and their fields as polyline shapefiles containing…
Sam
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22
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3 answers

Where to get street data in an importable format?

I don't want to use WMS layers, but to actually store the data in my local server, where can I find street data from the world?
Vinko Vrsalovic
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22
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5 answers

How to change page size in QGIS Composer

I've made a few maps in QGIS Composer and set them up initially as 8.5x11 page size. I want to begin with that layout and apply it to 11x17 page size. However when I change this in the Page Layout, only the page dimensions change. The symbol…
cndnflyr
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22
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3 answers

Adding Direction and Distance into attribute table in QGIS

I just want to add direction (Bearing: i.e N 25 35 E) and Distance (Length: 125 meters) as my new field in polyline/line data. Is there a Plugin to generate these fields? I tried to used Export/Add geometry columns in my line data, but only "Length"…
arzandia
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22
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2 answers

Precision when working with spatial data in GIS

Is there a basic or introductory study that examines and compares the precision of spatial data when working with varying precison of the data input, like having 1, 2, ... decimal places? with the varying implementations of floating points (float,…
oschrenk
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22
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5 answers

How to validate GeoJSON?

I have a small script that I'm using to generate GeoJSON data from a data format not currently supported by GIS software. I would like to validate the output, but when I use ogr2ogr to read it, it doesn't give me any helpful information about what…
BenjaminGolder
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22
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1 answer

Comparison of geocoding solutions (such as Gisgraphy & PostGIS 2.0)

As I am sure many of you are aware, PostGIS has finally released Version 2.0 and included within this version they have also built a geocoder (see: http://postgis.net/docs/Extras.html). Although I realize V2 was just released I am curious to know if…
NetConstructor.com
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22
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7 answers

How do you convert OSM XML to geojson?

I want to take the XML output of a Xapi query and display it using leaflet or polymaps. How can I do that? Is there an easy way to convert XML to geojson
null_radix
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4 answers

How to export shapefile to SpatiaLite

I have a shapefile with one layer. I can open it with QGIS. Now I want to convert this shapefile or layer to Spatialite database. How can I do it? Is it possible to do with QGIS?
Shahjalal
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22
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3 answers

Merging polygons in shapefile based on field values?

I have a shapefile with a lot of polygons in it. These polygons are grouped into a category: district. How can I merge the polygons based on the same name of the category within this shapefile?
Seen
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22
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3 answers

Check if a point falls within a multipolygon with Python

I have tried several examples of code using libraries such as shapefile, fiona, and ogr to attempt to check whether a point (x, y) falls within the boundaries of a multipolygon created with ArcMap (and thus in shapefile format). However none of the…
spartmar
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22
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4 answers

Optimal video cards for GIS programs

I recently purchased a Dell XPS-8300 (i7-2600|16 GB DDR3 RAM|64-bit Windows7) which I intend to use primarily for GIS programs. I bought a refurbished model because it was much cheaper and because I am able to choose a graphics card of my own. I am…
THX1138
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