All Questions

I have latitude and longitude as 19.0649070739746 and 73.1308670043945 respectively. In this case both coordinates are 13 decimal places long, but sometimes I also get coordinates which are 6 ...

What's the difference between a projection and a datum?

Oftentimes when we make maps it is based on our subjective interpretation of what is aesthetically pleasing. I would like it if people posted examples of beautiful maps, displaying any phenomena in ...

The discussion at What is the difference between WGS84 and EPSG4326? shows that 4326 is just the EPSG identifier of WGS84.. Wikipedia entries for Google Maps and OpenStreetMap shows that they both ...

I have spent around 2 days to find the way to open GDB (Esri geodatabase) in QGIS (or any other open source software) but still without success. I have downloaded the newest OSGeo4W installer and ...

ArcGIS Desktop has the option of using basemaps from ArcGIS online. Does QGIS have any such options?

Note: This question is specifically about installed, desktop software. There is another question specifically about free cloud-based software and services. What free programs should every GIS user ...

I am working on a web-based mapping system and I'm trying to figure out which library to use. These are links to comparisons of available libraries: Laurent Jegou's benchmark (from 2010) is a global ...

I would like to be able to script some things that are not exposed via arcgisscripting or ArcPy. How do I access ArcObjects from Python?

What is the difference between WGS84 and EPSG 4326? It seems like for a given dataset it might be both WGS84 and EPSG:4326.

Convex Hull A convex hull of a shape is defined as: In mathematics, the convex hull or convex envelope for a set of points X in a real vector space V is the minimal convex set containing X (...

I'm looking for an algorithm which when given a latitude and longitude pair and a vector translation in meters in Cartesian coordinates (x,y) would give me a new coordinate. Sort of like a reverse ...

Depending on what you read, 7 to 15% of the general population has some form of colour blindness. Can this be accounted for in map designs and, if so, how?

I am listing some of the acronyms used in our work and had to stop to think about whether to list these together or separately: DEM: Digital Elevation Model DSM: Digital Surface Model DTM: Digital ...

I'm looking for spatial clustering algorithm for using it within PostGIS-enabled database for point features. I'm going to write plpgsql function that takes distance between points within the same ...

My users are sending me point data that were digitized using Google Earth. How can I convert their KML to a shapefile?

I was debating with one of my collegues on OpenLayers v/s Leaflet. I made a point that OpenLayers is much better API if we wish to build a project, where you need direct connectivity to the Geoserver ...

I have a Shapefile but its coordinate system is Unknown, and there is no *.prj file. How can I identify it now?

Can anyone explain how to install GDAL/OGR with Python on Windows? I have Windows Vista and I have tried following the information on the website and it does not seem to bind the exe files for me. ...

Can anyone provide me with a link (or some details) on the actual ratio to "zoom level" figures for Google Maps? e.g. Google Maps Level 13 = 1:20000

My company uses geometry (the_geom) data type for storing geospatial data. I've recently been acquainted to the concept of geography (the_geog) data type which, as I understand it, stores the SRID ...

I am using Mapinfo and it has Y as latitude and X as longitude. Is that the same case for all mapping software? As for any country their respective value is multiple of 1 or -1. So for Nepal can I say ...

I've imported several shapefiles which where exported from a Mapinfo .tab. Several tab files are imported resulting in 20+ layers. Afterwards I want to export it to geoJSON; but I'm reluctant to ...

I have been reading a lot about PostGIS, but I am struggling to find a good beginner's guide. Which tutorials/books do you recommend?

As presented in a talk at FOSS4G Mapbox Studio allows to create Mapbox vector tiles and export them as a .mbtiles file. The mapbox-gl.js library can be used to dynamically style and render Mapbox ...

I want to start working on a web map at work to map some of our statistics by city. I have an idea, but I'm not exactly sure where to start. Are there any definitive resources that provide step ...

How do you manage your geospatial data? I have terabytes of data spread out over hundreds of datasets, and have an ad-hoc solution using symbolic links within projects which link back to an domain-...

For someone studying to pursue a career as a GIS Analyst, what math courses should he/she take? Here's a long list of free Math courses from MIT to serve as a frame of reference. Which are essential,...

What books, journals, and/or electronic resources have you found most valuable for expanding your knowledge in the GIS field, and why?

How do I calculate areas of an area shapefile in square meters or in acres (ha)? I didn't find that functionality in the vector tools.

Well, since it was one of the highest rated proposed questions, hasn't been asked yet, and I would love to know the answer, I thought I'd ask it. How do I explain what GIS is for the 11 year old kid?

As you see in the figure, the question is: How to find the minimum-area-rectangle (MAR) fitted on the given points? and a supporting question is: Is there any analytical solution for the ...

I'm trying to get a sense if this is an issue for others or every input/output should be labeled so user is not confused and just go with it? I think almost everyone pronounces it as "LatLon". Who ...

A poorly designed map can not only look visually unappealing, but can convey the wrong message, which could lead to bad decisions being made. I would like to ask people to post examples (that are in ...

I am new to Python scripting in ArcGIS but not new to ModelBuilder. I would like to know the benefits of Python vs ModelBuilder. When should we write Python script for GIS automation rather than ...

I seem to use ESRI's Arcpy site package for virtually all of my python geoprocessing. To ESRI's credit, these are an incredible suite of tools that can help accomplish a great deal. However, I would ...

I asked this question on Stack Overflow before I realised this site existed. As this site it more appropriate, I'll ask it here too. I'm trying to install gdal from pip pip install gdal inside a ...

I would like to rename some fields in my attribute table: Like rename XRF_N3in something else. It seems quite a easy issue but I don't find any information about how can I do that... I've QGIS 1.8 in ...

What is the main difference between a Web Map Tile Service (WMTS) and a Web Map Service (WMS) When should you choose one over the other? What are the (dis)advantages by choosing one over ...

A very simple question: Is there a simple tool in QGIS to graphically visualise geometry formatted as text? Example geometry: "POLYGON((571178 6337246,571178 6402217,598061 6402217,598061 ...

Recently I've been spending a lot of time converting perfectly good field names like "Percent of citizens age 25 and over with a bachelor's degree or higher" into things like "edbchogtr" to meet the ...

This line: SELECT geom FROM myLayer.geom will return a hex value. How would I get decimal values, which is a human-readable coordination?

Suppose I have geographic coordinates of "Saratoga, California, USA" as Latitude: 37°15.8298′ N Longitude: 122° 1.3806′ W I know from here that in case of latitude 1° ≈ 69 miles and that ...

Using ArcGIS, QGIS, Grass, and/or GVSIG: What are some of the tools and processes involved in building effective heat maps? What are the plugins involved? What are the major data requirements? What ...

I need to open a shapefile from ArcMap in R to use it for further geostatistical analysis. I've converted it into ASCII text file, but in R it is recognized as data.frame. Coordinates function doesn't ...

How to create, on the shape of a polygon, a regular grid of polygons/squares of an given size, in postgis? I have thought about a function like How to create regular point grid inside a polygon in ...

I know that ArcGIS is available for Android, but does anyone know of any other GIS apps that are available for Android tablets?

What level of error do I encounter when approximating the earth as a sphere? Specifically, when dealing with the location of points and, for example, the great circle distances between them. Are ...

I have been using Postgis 2.0 for 3/4 of a year now and while I really enjoy using it, excessive query processing time has rendered it basically unusable for my use case. I tend to do heavy ...

Imagine you're tracking, for example, vehicle or animal movement and receive regular GPS position updates. How would you visualize speed of movement on a static (= printable) map? I've been coloring ...