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41
votes
5answers
59k views

Smoothing/generalizing polygon in QGIS?

Is it possible to smooth or generalize a polygon in QGIS, perhaps by using a plugin like the generalizer-plugin for lines? I could convert my polygons to lines, smooth them and convert them back to ...
41
votes
5answers
119k views

Showing popup on mouse-over, not on click using Leaflet?

Is it possible in Leaflet that popup opens on mouse-over, not on click? This is working for just one marker at a time, but I need it for a bigger number of markers: marker.on('mouseover', function(e)...
41
votes
4answers
60k views

Deciding what interpolation method to use for resampling raster data?

Are there hard and fast rules about which interpolation methods are suited to each kind of raster data?
41
votes
4answers
41k views

Joining non-spatial CSV file to spatial data (shapefile) using QGIS?

I have a CSV file which has postcode data in a field, but it is non-spatial e.g. no Easting and Northing. I have a shapefile with postcode in a field and some additional data. I want to join the ...
41
votes
7answers
17k views

Comparing two spatial point patterns?

If I have two point pattern distributions within the same geographic region, how would I go about visually and quantitatively comparing those two distributions? Also assume I have many points within ...
41
votes
5answers
35k views

Making beautiful maps in R? [closed]

There are quite some nice possibilities to analyse spatial data in R and in the context of my current project I would like to use R more frequently to do that. Until now I plot my maps with ggplot2 ...
41
votes
1answer
7k views

Coordinate system for accurately calculating areas of polygons that cross UTM Zones?

I have multiple polygons, all located offshore around the UK. I am trying to calculate the areas of these polygons in square kilometres, without splitting them by UTM zone. Is it possible to do this ...
40
votes
2answers
42k views

How can I convert data in the form of lat, lon, value into a raster file using R?

I have a data set of values over a km grid in the continental U.S. The columns are "latitude", "longitude", and "observation", e.g.: "lat" "lon" "yield" 25.567 -120.347 3.6 25.832 -120....
40
votes
5answers
35k views

How to determine if a tiff is georeferenced or not?

I received a tiff file from someone, but I'm not sure if it's georeferenced. Is there an easy way to check this?
40
votes
4answers
35k views

Where does QGIS write its error log messages?

I want to read and copypaste the error log for the crashes I am experiencing in QGIS 2.0. The error I am getting freezes QGIS so I have to ctrl-alt-del. I can see the last message in the panel, but ...
40
votes
1answer
17k views

Is WGS84 itself a Coordinate Reference System?

I was wondering the difference between WGS84 and EPSG:4326 (see this). Can then WGS84 on its own be defined as a Coordinate Reference System? Or is it just a datum so that a Coordinate System must ...
39
votes
16answers
6k views

Using Computer Games to display GIS data?

Besides being a GIS user I'm a big computer game fan. Games like Civilization, Minecraft, World at War and many others have a very powerful engine to display huge maps in a beautiful way. Is it ...
39
votes
4answers
9k views

Using directional shading on boundaries for cartographic effect in ArcGIS Desktop?

The attached screenshot of a National Geographic map shows some beautiful directional shading of boundaries. I'm trying to reproduce this sort of shading for a burn perimeter map, as I want to ...
39
votes
5answers
12k views

Curved point-to-point “route maps”

I have recently been looking at airlines web pages that display their routes departing a certain city to all other cities they service. I would like to be able to create similar curved routes between ...
39
votes
11answers
50k views

Where to get 2010 Census Block data?

I would like to download 2010 Census Block Data for several towns and I can't seem to find it on American Factfinder. Is it there? And if not, does anyone know where I could find it?
39
votes
3answers
43k views

Manually placing labels in QGIS?

Is there a way to manually place labels in QGIS? I have a map which has almost-duplicate labels in some places (e.g. E 1st St and 1st St) and I'd like to remove some of them. Also, I'd like to ...
39
votes
4answers
12k views

How to migrate from ArcGIS for Desktop to QGIS? [closed]

Our lab has about 10 projects in ArcGIS 9 (a couple are made in ArcGIS 10) that includes the following in each: A georeferenced (WGS1984 geographical projection) raster seafloor image, representing ...
39
votes
6answers
21k views

Migrating geodatabase data into PostGIS without Esri apps?

Can you tell me how I can load geodatabase data into PostGIS without having to install Esri apps? The solution I found online talked about using ArcGIS to convert GDB to SHP and then importing SHP ...
39
votes
1answer
36k views

Finding center of geometry of object?

Given a set of 2D or 3D points: How to find the center of geometry of an object? According to the following figure, the center of geometry differs from the center of mass if it is calculated in the ...
39
votes
3answers
15k views

Convert GeoJSON to TopoJSON

How can GeoJSON data to TopoJSON be converted? TopoJSON files are often smaller than GeoJSON and the conversion allows you to incrementally simplify a dataset, if you wish.
38
votes
15answers
104k views

Converting MapInfo TAB and/or MIF to SHP using free tools or ArcGIS for Desktop core product?

How do I convert MapInfo TAB and/or MIF files to SHP using only free tools or ArcGIS itself? I've not had much luck trying to do this in the past and I don't want to have to shell out for the ArcGIS ...
38
votes
4answers
23k views

SQL query to have a complete geojson feature from PostGIS?

I would like to get a geojson feature with properties from PostGIS. I have found an example to have a feature collection but I can't make it works for just a feature. SELECT row_to_json(fc) FROM ( ...
38
votes
6answers
21k views

Shapefile PRJ to PostGIS SRID lookup table?

I was wondering if there is such a thing as an shapefile PRJ to PostGIS SRID lookup table? Something that can translate the most standard shapefile PRJ definitions into the likely SRID. When using ...
38
votes
5answers
24k views

How best to fix a non-noded intersection problem in PostGIS?

I'm using a PL/R function and PostGIS to generate voronoi polygons around a set of points. The function that I am using is defined here. When I use this function on a particular dataset I get the ...
38
votes
4answers
7k views

Performance of ArcGISScripting and large spatial data sets

I am currently writing a python script using the arcgisscripting module to process a reasonably large data set (~10,000 records in total) normalised over a small number of tables, 8 in total. The ...
38
votes
3answers
33k views

How to run a simple python script for QGIS from outside (e.g. Sublime Text)?

I would like to run a few small and simple python scripts for QGIS (Mac) from "outside" of QGIS. With outside I mean in this context, either the normal os command line (terminal.app) or even better, ...
38
votes
2answers
42k views

How do I check which version of GDAL I have and how many?

I have installed in my computer the following software: PosgresSQL 9.3.2.3 PostGIS 2.1.1.1 QGIS 2.0.1 Dufour (this one installed through the OSGeo4w package) QGIS 1.7.0 Wroclaw As far as I know all ...
38
votes
1answer
12k views

Using GeoPackage instead of SpatiaLite, and vice-versa?

I am using now QGIS 2.18, which includes support for GeoPackage format. I know that GeoPackage is like a replacement for Shapefile but not quite so, as GeoPackage has database capabilities. At same ...
37
votes
21answers
31k views

Connecting to PostGIS database from ArcMap for display and query without ArcSDE?

How can I connect to a PostGIS database from ArcMap using ArcGIS Desktop 9.3 and later? I would like to be able to perform spatially enabled queries and receive the results back (e.g. spatial and non-...
37
votes
6answers
28k views

Learning ArcPy?

Where can I start to learn ArcPy?
37
votes
4answers
26k views

Simple thematic mapping of shapefile using Python?

I wish to visualize geographical data in Python, without using ArcGIS/ArcPy, and make a map. On the internet I found how to make a thematic map using Python: Here is some code that I tried: ...
37
votes
7answers
8k views

Machine Learning Algorithms for Land Cover Classification

I am interested in learning what software exists for land classification using machine learning algorithms (e.g. k-NN, Random Forest, decision trees, etc.) I am aware of the randomForest package in R ...
37
votes
7answers
41k views

How to create polygons with straight lines and right angles in QGIS?

When creating a polygon, how do I do it so that the lines are straight (90, 0 degrees, etc.) and when I create corners they can be right angles? For instance, how do I create a perfect square or ...
37
votes
4answers
26k views

Is there an automatic function in QGIS to package all files in a project for transferability?

In my project, I use a lot of geodata from different directories. Now I want to give the QGIS project to a colleague (eg on a CD). Is it possible to copy the shapes from different directories ...
37
votes
10answers
31k views

Open Source Tool capable of reading Esri File Geodatabase (.gdb)?

I have an ESRI File Geodatabase (.gdb) file that I would like to convert to shapefile (or any other non-proprietary format). Are there any Open Source tools to do so?
37
votes
4answers
60k views

Loading OpenStreetMap data in QGIS?

In QGIS 1.8 I used the openstreetmap plugin to request data from the server, or open a .osm XML file, which produced 3 layers (polygons, polylines and points) in QGIS. This was great (give or take ...
37
votes
4answers
33k views

How to insert a GeoJSON polygon into a PostGIS table?

I need to insert a polygon from GeoJSON to my PostGIS table. This is how the SQL query looks like. INSERT INTO tablename (name, polygon) VALUES ( 'Name', ST_GeomFromGeoJSON( '{ ...
37
votes
6answers
37k views

Difference between map layer and spatial dataset (e.g. feature class, shapefile)?

What is the difference between a feature class and a feature layer? To me they seem very similar in concept.
37
votes
7answers
20k views

Nearest neighbor between point layer and line layer? [closed]

I've asked this question several times on stackoverflow and irc between #qgis and #postgis and I also tried to code it or implement it my self in postgis with no real answer. Using programming (most ...
37
votes
2answers
58k views

Projecting sp objects in R

I have a number of shapefiles in different CRSs (mostly WGS84 lat/lon) that I'd like to transform into a common projection (likely Albers Equal Area Conic, but I may ask for help on choosing in ...
37
votes
2answers
18k views

Fastest way to count the number of features in a feature class?

With the introduction of the Data Access module in arcpy (30x faster search cursors), I want to know if counting features matching sql criteria is faster than the traditional MakeTableView + GetCount ...
37
votes
4answers
12k views

Separate polygons based on intersection using PostGIS

I have a PostGIS table of polygons where some intersect with one another. This is what I'm trying to do: For a given polygon selected by id, give me all of the polygons that intersect. Basically, ...
37
votes
12answers
9k views

What is the state of the art in html5 geospatial applications?

I am very interested in the HTML5 canvas element for maps; work like Cartagen from an MIT Media Lab researcher looks very promising, for example. There is some interesting SVG based work at carto.net....
37
votes
7answers
6k views

Interrupting contour lines beneath elevation labels (instead of using label buffers) using QGIS?

Is there a way to interrupt a contour line beneath an elevation label using QGIS?
37
votes
1answer
22k views

Defining new custom projections in QGIS?

I'm trying to define a projection in QGIS. I want to add North America Albers Equal Area Conic. From the spatialreference site I copied the proj4 line: +proj=aea +lat_1=20 +lat_2=60 +lat_0=40 +lon_0=-...
37
votes
2answers
3k views

What coordinate system should be used to store geography data for celestial coordinates?

I am doing an astronomy project. I want to have the information about our images stored in a spatially enabled database. This, I would think, should be a very easy special case for GIS functions ...
36
votes
12answers
64k views

Exporting feature class into multiple feature classes based on field values using ArcGIS Desktop?

I have a feature class with over 2,000 features, and I need to make them all individual feature classes based on a field. Is there a way to do this?
36
votes
7answers
32k views

Using continuous color band for raster legend in QGIS composer legend?

I'm looking for a way to insert continuous colour legend for a raster layer. I managed to create discrete symbols with values along the bar, but I would like to have a continuous bar with some values ...
36
votes
8answers
64k views

How to determine the centroid of polygons?

I have a polygon vector and I want to quickly attain the centroid of this polygon for insertion in a text document. I am working with QGIS. I searched through other questions and although some are ...
36
votes
2answers
65k views

Clipping a raster in R

I am building a map for the northeastern U.S.A. The map background needs to be either an altitude map or a mean annual temperature map. I have two rasters from Worldclim.org which give me these ...

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