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37
votes
3answers
33k views

Ignoring invalid input features with Intersection tool in QGIS?

In QGIS 2.18, when I used the Vector > Geoprocessing Tools > Intersection tool, I was able to check an option which said "Ignore NULL geometries [optional]". Now I've downloaded QGIS 3.2 and that ...
37
votes
6answers
38k 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
12answers
30k views

How would I draw and visualize custom maps based on OSM data?

I would like to be able to use openstreetmap data for a specific region as a source and "draw" from that the map of infrastructure improvements - mostly roads. I want it to be self-hosted (not ...
37
votes
1answer
22k views

QGIS 3 Plugin folder location

I am searching for default location for QGIS 3 Plugin folder I checked here but could not find : C:\Program Files\QGIS 3.0\apps\qgis\python\plugins C:\Users\Abhijit.qgis2 (cannot locate .qgis3, ...
37
votes
7answers
21k 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
61k 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
4answers
28k views

Selecting features with NULL attributes in QGIS?

How do I identify which features have NULL attributes in the attribute table of a shapefile? When i try [field]= 'NULL' it selects the features with value = 0 (see picture)
37
votes
2answers
19k 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
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
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
2answers
3k views

Choosing coordinate system 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
4answers
34k views

Filling column with consecutive numbers in QGIS?

I make a new column in my attribute table and it has a default value (for example 0). I want to (probably using the field calculator) have the result that row 1 has the value 1, row 2=2 and so on, ...
36
votes
2answers
72k views

Clipping 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 ...
36
votes
5answers
37k views

Why does PostGIS installation not create a template_postgis?

I went this route for installation of PostgreSQL and PostGIS: PostgreSQL using the standalone KyngChaos, PostGIS install from KyngChaos as well... pgAdmin3 from PostgreSQL Tools Now when I launch ...
36
votes
5answers
8k views

Advantages of using spatialite over shapefile? [closed]

I found spatialite more useful than shapefiles as it does not have the limitations of shapefile and it is also portable. Many people here use shapefiles to exchange data and even the experts do not ...
36
votes
3answers
36k views

Best GIS system for high performance web application - PostGIS vs MongoDB

I am working on a web/mobile application based on location data. Since i am already familiar with MongoDB, i found the geospatial indexing of mongo is quite suitable for my needs. As i am mainly ...
36
votes
7answers
101k views

Creating new layer from selection in QGIS?

Is it possible to create layers from selection in QGIS? I am using QGIS 1.7.4-Wroclaw. To make it easier for others to see this, here are some pics. I used QGIS 2.0.1-Dufour. SELECT SAVE ADD
36
votes
9answers
87k views

Online WKT and GeoJSON viewer

I once found a great but simple webpage that has a drop down with several text-based GIS formats such as GeoJSON and WKT, and a text box to copy/paste your data. The feature is then drawn on a world ...
36
votes
6answers
30k views

Visualizing large datasets with Leaflet

When using Leaflet to visualize a large dataset (GeoJSON with 10,000 point features), not surprisingly the browser crashes or hangs. A sub-sample of 1000 features from the same dataset works ...
36
votes
4answers
28k views

Overlaying spatial polygon with grid and checking in which grid element specific coordinates are located using R [closed]

How can one use R to split a shapefile in 200 meter squares/sub-polygons, plot this grid (incl. ID numbers for each square) over the original map below, and evaluate in which square specific ...
36
votes
4answers
19k views

GIS professionals working from home?

How many of you out there work from home? What kind of company / organization do you work for (private, government, municipal, institution..?). How did you convince your employer it was a good idea? ...
36
votes
4answers
47k views

Why is GPS a free service?

The Global Positioning System (GPS) is a free service that is owned and operated by the U.S. Government and is always available. When we buy a GPS device, we don't pay a monthly fee or pay a tax for ...
36
votes
3answers
4k views

Why are Data Projections relevant?

Why is it useful to store data in unusual projections and datums? I understand the value of projections as output constructs, because of distortion, etc: that much is justifiable. However, I don't ...
36
votes
9answers
86k views

Can QGIS open KMZ files?

I know I can add KML files once I have unzipped the KMZ files, but is there a way to open KMZ files directly? When I try to open a kmz file on QGIS 1.8.0 on Windows XP, through the all files filter, ...
36
votes
5answers
10k views

Reprojecting raster from 0 360 to -180 180 with cutting 180 meridian using gdalwarp

I have a geotiff raster image that has a coordinate system with longitudes from 0 to 360. The horizontal center of the image is 180 longitude. See image below: I want to transform it to EPSG:4326 SRS ...
36
votes
5answers
8k views

Generalizing polygon file while maintaining topology in QGIS?

I have a polygon Shapefile, which I need to generalize. How can I generalize the poligons and ensure that there are no topological errors like "slivers". I already tried: Vector -> Geometry Tools -...
35
votes
37answers
14k views

Great GIS, maps & cartography quotes [closed]

Programmers' list has been a pleasure to read. Stats' list is growing fast as well. So perhaps there is a place for separate one on this site? Please share your nuggets of wisdom / humour / ...
35
votes
5answers
52k views

How to write Shapely geometries to shapefiles?

Can someone demonstrate a simple way to write geometry data-structures from shapely into shapefiles? I am particularly interested in polygons with holes and linestrings. It would also be beneficial to ...
35
votes
9answers
80k views

Generating random locations nearby?

I am trying to create random locations nearby my location. What i want is to create random latitude/longitude pairs inside a 200 meters circle surrounding my location. This is the formula i came up ...
35
votes
2answers
21k views

Setting print layout to portrait using QGIS 3?

I can't get the print layout to appear in portrait. It opens in landscape and Layout/Page Setup... allows for portrait, but the layout canvas remains in landscape. In 2.18 the "Composition" Panel ...
35
votes
3answers
49k views

Displaying only selected features on map in QGIS?

Not sure if this option ever existed, but the new QGIS version hides a lot of things somewhere else and this seems so simple that I'm kind of convinced it was possible to do this before. I have quite ...
35
votes
10answers
64k views

Adding Attribute data to shapefile?

I can display a shapefile in openlayers but I need to add some attribute data. I can open the dbf file in excel but there is no save as option in excel to the updated file as a dbf. What is the ...
35
votes
3answers
25k views

What is the proper syntax and usage for ArcGIS “in_memory” workspace?

I am unclear how best to use the in_memory workspace in ArcGIS. The best resource I have found on the subject is from ESRI on Using in-memory workspace. Unfortunately, the help section is not very ...
35
votes
2answers
50k views

Adding shapefiles to PostGIS database

I was able to create a Postgresql database and then I executed, createlang plpgsql geospecies psql -d geospecies -f postgis.sql psql -d geospecies -f spatial_ref_sys.sql So now can I directly import ...
35
votes
1answer
31k views

How to convert/typecast from Polygon to Multipolygon in PostGIS?

Is there any way to typecast Polygons to Multipolygon type? For example, I have created a circle using ST_Buffer() on a point. The return type of that function is of Polygon type. The problem is that ...
35
votes
3answers
5k views

Creating transparent hillshade?

I get elegant transparent hillshades via a combination gdal and convert. Compare to grey-based hillshade commonly used, such transparent hillshades are very cool because they can be placed between the ...
35
votes
2answers
71k views

Enabling “Snapping” in QGIS while drawing polygons?

I tried to draw polygons in QGIS 1.7.0 and somehow I can't find or failed to find the "Snapping" option. I'm used to ArcGIS 10.0 where you have some snapping options, like placing points of polygons ...
35
votes
3answers
15k views

Is there a Carto CSS Gallery which also contains code?

I am currently exploring the usage of CartoCSS and TileMill in one of our projects. I have seen the impressive gallery available at http://www.mapbox.com/tilemill/gallery/ The gallery looks ...
35
votes
6answers
22k views

Joining attributes from nearest point in QGIS?

I have two layers with points, call them A and B, each with different attributes. For each point in A I want to join all the attributes from the nearest point in B. Ideally this would also include ...
35
votes
5answers
18k views

Is there a way to render lines with a smooth (bezier) curves in QGIS?

I am moving from creating maps with Illustrator to making them with QGIS and actual data. One of the things I haven't been able to re-create in QGIS are the smooth curved lines I can get in ...
35
votes
7answers
43k views

Clustering spatial data in R? [closed]

I have bunch of data points with latitude and longitude. I want to use R to cluster them based on their distance. I have already taken a look at this page and tried clustTool package. But I am not ...
35
votes
3answers
1k views

Learning to think spatially rather than just follow point and click tutorials

The college I work for is considering revamping their intro to GIS course. Traditionally, they've used the ESRI suite but are now open to using other options. There are two factors responsible for the ...
35
votes
7answers
27k views

Creating shapefile showing footprints of Rasters?

I have around 1,000 satellite images in tiff format, and I want to create a shapefile which will serve as an index to the rasters. This is something similar to a raster catalog, but I do not want to ...
35
votes
4answers
50k views

Creating DEM from contours in QGIS?

I have a shapefile with contours and their heights. Is it possible to make a DEM from contours in QGIS without using GRASS? I found Creating DEM from contours using ArcGIS Desktop? but the answer ...
35
votes
5answers
45k views

Comparing different open source GIS servers?

I currently know the following open source GIS servers: Geoserver: java based, vector and bitmap support, also supports. Is now on par with mapserver (performance-wise). mapserver: c/c++, used to be ...
35
votes
5answers
17k views

Identifying clusters in vector point data using QGIS?

I have a vector dataset of rural broadband data-points (how fast, etc.) and I'd like to explore if there are clusters of points with similar characteristics, and to plot polygons encompassing them. ...
35
votes
2answers
16k views

Looking for fastest solution for Point in Polygon analysis of 200 million points [closed]

I have a CSV containing 200 million observations with the following format: id,x1,y1,x2,y2,day,color 1,"-105.4652334","39.2586939","-105.4321296","39.2236632","Monday","Black" 2,"-105.3224523","39....
35
votes
6answers
3k views

Is there GIS Video “that Mom can understand”?

Working as a professional within the GIS discipline, I often find it challenging to describe to people what GIS is (in a face to face conversation). Telling them that GIS stands for Geographic ...
35
votes
2answers
16k views

Proper workflow for LAS to DEM conversion

I regularly come across LiDAR (.LAS) files with elevation data. When I do, I always struggle to find a way of converting them to a DEM for hydrological analysis. I have developed several workflows, ...

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