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36
votes
8answers
33k 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
2answers
67k 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 ...
36
votes
5answers
36k 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
3answers
34k 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
12answers
28k 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 ...
36
votes
5answers
63k views

Splitting shapefile into separate files for each feature using QGIS/GDAL/SAGA?

I have a polyline shapefile with about 20 kinds of roads. I would like to know how can I create automatically a vector file for each one. I am aware of how to do it using ArcGIS for Desktop - see ...
36
votes
7answers
241k views

Export Google Maps Route to KML/GPX

Since Google pulled the plug on Google Maps Classic, I'm reluctantly moving to its Google Maps New application. However, I didn't find how to export a route to a GPX or KML file so it can be copied ...
36
votes
6answers
29k 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
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
25k 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)
36
votes
6answers
48k views

Trilateration using 3 latitude/longitude points, and 3 distances?

I want to find out an unknown target location (latitude and longitude co-ordinates). There are 3 known points (latitude and longitude co-ordinate pairs) and for each point a distance in kilometers to ...
36
votes
4answers
45k 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
5answers
7k 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
112k views

Exporting attribute table to Excel from QGIS?

I have seen all the questions for how to export an attribute table to Excel from QGIS, and I try all the answers like copy paste, CSV (in fact this I do not know where to find), but none seems to be ...
35
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 ...
35
votes
4answers
26k 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 ...
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
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 ...
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
26k 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
5answers
44k 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
9answers
84k 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, ...
35
votes
5answers
16k 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
5answers
9k 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 ...
35
votes
2answers
15k 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
2k 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, ...
35
votes
9answers
19k views

Is there a good GPS track analysis library?

I keep writing custom code to work with GPS tracks: GPX files and NMEA logs from my phone, dedicated GPS logger, etc. I feel like I'm reinventing the wheel and am wondering if there's some standard ...
35
votes
0answers
18k views

How to use PostgreSQL/PostGIS with ArcGIS for Desktop? [duplicate]

Has anyone used PostgreSQL with PostGIS successfully? I am a semi-experienced ArcGIS user and want to build out a database and connect it to ArcCatalog. I've scoured the internet for resources but ...
34
votes
4answers
30k 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, ...
34
votes
6answers
37k views

Creating square buffer around point feature using ArcGIS for Desktop?

I would like to create a square buffer from a point feature but I do not understand the code that goes into it. Similar questions have been asked on the forums.esri website but that was over 10 ...
34
votes
5answers
19k views

Change style properties of several layers simultaneously?

I'm working on bulk data. I have a few hundred GeoTIFF images imported into a QGIS project, and I'd like to modify their layer properties - things like the no-data-value, transparency of certain pixel ...
34
votes
10answers
62k 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 ...
34
votes
3answers
44k 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 ...
34
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 ...
34
votes
7answers
94k 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
34
votes
9answers
77k 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 ...
34
votes
3answers
4k 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 ...
34
votes
10answers
12k views

Seeking alternatives to pgRouting for open source routing / network analysis?

I was wondering if there are any alternatives to pgRouting tools. Thinking about it for a bit, I think the only alternative is to use R or RPY to do the analysis. Basically I'm trying to solve ...
34
votes
3answers
65k views

Draw lines from points in QGIS

I have a point layer and need to draw a line passing through or in the vicinity of the points (up to 0.5m ditance between the point and the line). The nodes of the line will recieve the attributes of ...
34
votes
7answers
40k 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 ...
34
votes
6answers
20k 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 ...
34
votes
4answers
29k views

Windows security warning (ActiveX) when clicking into fields in ArcToolbox tool?

I have been running ArcGIS 10.5 on my PC (Windows 10 Home) since December with no issues. This past week I have started to get ActiveX Security Warnings when I click into a parameter field in any ...
34
votes
2answers
17k views

Styling road maps with QGIS?

I am trying to design a beautiful map using QGIS. There is a similar question here Seeking QGIS tutorials and web resources? but I would like to focus on "designing a map using QGIS". I was looking ...
34
votes
4answers
46k 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 ...
34
votes
5answers
19k views

Increasing speed of crop, mask, & extract raster by many polygons in R?

I'm extracting the area and percent cover of different land use types from a raster based on several thousand polygon boundaries. I've found that the extract function works much faster if I iterate ...
34
votes
5answers
39k views

Converting .shp into .gpx using QGIS?

I would like to convert .shp into .gpx. Using GIS, I open my shapefile and I tried to "save as" gpx but it gives an OGR error: creation of field ObjectId failed (OGR error: Field of name '...
34
votes
2answers
3k views

Streamlining Python Code for Big Data

I have Python code which is designed to take point shapefiles through the following workflow: Merge points Integrate points, such that any points within 1 m of each other become one point Create ...
34
votes
3answers
6k views

How to represent trend over time?

I have a time series of rasters where the cells of each raster represents some value at a certain time. I would like to generate a map that highlights the magnitude of positive or negative trends in ...

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