All Questions

Filter by
Sorted by
Tagged with
64
votes
3answers
89k views

Installing latest QGIS version on Ubuntu? [closed]

I am relatively new to Linux, so can you indicate the exact commands (step-by-step) that I need to type to get the latest QGIS installed on Ubuntu 14.04. I have tried to follow the instructions ...
64
votes
2answers
17k views

How accurate is approximating the Earth as a sphere?

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 ...
64
votes
1answer
50k views

Choosing SRID and what is its meaning? [closed]

I'm new to GIS, in PostGIS, and I'm struggling with the SRID concept. How do you choose a SRID for a database column? This is making me crazy. Why do I need to choose a SRID? What's its meaning? ...
64
votes
5answers
100k views

Seeking Mobile GIS applications for Android Tablets? [duplicate]

I know that ArcGIS is available for Android, but does anyone know of any other GIS apps that are available for Android tablets?
63
votes
6answers
128k views

Loading external GeoJSON file into Leaflet map?

I would like to load a geoJSON (polygon) file into my leaflet map. I have seen examples where geoJSON is embedded into the javascript code but I can't find any examples showing how it is done with an ...
63
votes
13answers
153k views

Running Create Extension postgis gives ERROR could not open extension control file?

I have installed PostgreSQL 9.x and PostGIS 1.5/2.0 several times and have never had this problem. I just got a new CentOS 6.3 server up and running and and I have Postgres 9.3 functioning as ...
62
votes
12answers
8k views

Visualizing speed of movement on static (= printable) map?

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 ...
62
votes
8answers
26k views

Should GDAL be set to produce GeoTIFF files with compression? Which algorithm should be used?

I have a folder of GIS data that consists mainly of GeoTIFF files. The whole set weighs in at about 1.2 GB. I noticed that if I pack the contents into a tarball, it smashes down to about 82 MB. I ...
62
votes
3answers
85k views

Layers with same coordinate system should align/overlap in ArcMap but do not?

I put 4 different layers into my ArcMap document, but only one of them will show up on the map! I should be seeing the other 3 layers as well. When I do a Zoom to layer, I can see one layer, but I ...
62
votes
8answers
70k views

Sources for US Zip Code Boundaries?

I was just wondering what the most up-to-date source for US Zip Code boundaries would be. My first thought was TIGER, whenever that comes out, but then I thought that the Postal Service might be a ...
60
votes
7answers
8k views

What strategies, criteria, or rules to use for selecting coordinate systems?

What strategies, criteria, or rules do you use for selecting coordinate systems for (a) storing, (b) analyzing, and (c) displaying GIS data? (I humbly offer my reply to a related question about ...
60
votes
5answers
97k views

Clipping raster with vector boundaries using QGIS?

I am using QGIS. I would like to clip a raster precipitation layer using an admin boundary layer that is vector data. However the geoprocessing tools seem to be usable only for vector data. How ...
59
votes
7answers
13k views

Creating Vector Polygons with rendering performance like GISCloud?

I have been looking for a solid solution which would allow me to create a web map and overlay vector polygons without taking forever to load such data with the goal of allowing me to make each polygon ...
59
votes
6answers
5k views

One dimensional map of the world?

Bit of a strange question but hope this is OK to ask here. Has anyone heard of a '1-dimensional' projection of the world map - that is mapping all the points on the globe to a single line? I was ...
59
votes
7answers
36k views

Generating Tiles with QGIS?

Is it possible to generate map tiles from QGIS? I guess QGIS Server must have a way to do it, but is there a way to just generate the tiles and save them to disk? With the new symbology renderer ...
59
votes
1answer
77k views

What are the differences between WMS, WFS, WCS, WPS?

By looking at I do not really understand the differences between WMS, WFS, WCS, and WPS. Can somebody please explain the differences between them?
58
votes
11answers
49k views

Seeking Free and Open Source GIS Desktop packages?

Can someone give me a list of free and open source GIS desktop packages?
58
votes
5answers
25k views

What are Esri's new ArcGIS for Professionals and ArcGIS Pro?

After looking through all the stuff that was released or talked about at the Esri UC 2013 I am still genuinely confused by what ArcGIS for Professionals is. I will admit that it looks pretty cool, ...
58
votes
3answers
25k views

Openlayers Animation Examples and Algorithms

i wonder for a long time if people in this community uses openlayers for animation needs. we have know this that animating on browser is a little bit exhausting for it but when a map meets with ...
57
votes
4answers
26k views

Extracting data.frame from simple features object in R

Is there an sf-native (i.e. "correct") way of extracting everything except the geometry column from a simple features object? This works df <- dplyr::select(as.data.frame(sf), -geometry) but the ...
56
votes
5answers
76k views

How to remove Esri basemap credits?

As you can see from the attached sample map, the Esri basemap credits are overpowering and reduce the cartographic design of the entire map. These credits appear to be new to 10.1 and essentially ...
56
votes
2answers
112k views

Inserting point into PostGIS?

I have created one table in my PostGIS nut I cannot insert point. What is wrong with my query? CREATE TABLE app ( p_id INTEGER PRIMARY KEY ); SELECT AddGeometryColumn('app','the_geom','4326','...
56
votes
4answers
13k views

Why has Web Mercator (auxiliary sphere) become the web map standard?

I understand what the difference is between the Web Mercator projection and Web Mercator Auxiliary Sphere (WMAS). I also understand that both Google and Esri have adopted this projection as their ...
55
votes
6answers
35k views

Why is the 'straight line' path across continent so curved?

This is the result of mapping the straight line path from a point in US to Poland using Distance Measurement Tool. Also, planes from Asia to US would travel almost over North Pole. Why is the path ...
55
votes
8answers
178k views

Importing DWG into QGIS project?

I have a lot of DWG files like basemap, and water and wastewater network. How do I import these files into my QGIS project?
55
votes
10answers
58k views

Removing small spaces (slivers) between polygons?

I have a set of polygons representing administrative districts. The districts were digitized by hand, and there are small spaces (slivers) between polygons where the polygons should be touching. How ...
55
votes
10answers
44k views

Creating drive time polygons using Open Source tools?

Is anyone using open source tools and/or data to generate drive time polygons that radiate out from a given location? For example, I have used ESRI products like Network Analyst and Business Analyst ...
55
votes
14answers
8k views

The GIS of War - Tracking Conflicts and Their Effects

I was idly speculating on the many sorts of things people are keeping track of these days with GIS - natural/human catastrophes, demographic and economic patterns, climate change, etc. In that vein, I ...
54
votes
2answers
63k views

Converting Pandas DataFrame to GeoDataFrame

This seems like a simple enough question, but I can't figure out how to convert a Pandas DataFrame to a GeoDataFrame for a spatial join? Here is an example of what my data looks like using df.head(): ...
54
votes
3answers
13k views

What is the purpose of PostGIS on PostgreSQL?

PostgreSQL already supports spatial data types, operators and indexing. What does PostGIS provide exactly that made it necessary to exist as an extension to PostgreSQL? Why don't we all just use ...
54
votes
6answers
80k views

Will the OpenLayers Plugin be updated for QGIS3?

Upon searching for the OpenLayers plugin, it shows that this plugin is incompatible with version QGIS 3.0. Will this be updated? Is there another way to add Google imagery or any other aerial imagery ...
54
votes
2answers
42k views

Changing SRID of existing data in PostGIS?

While importing my shapefile data to PostGIS, I did not select the proper Projection. How do I now change the SRID of the data, without transforming the Coordinates?
54
votes
5answers
14k views

What are the benefits of hexagonal sampling polygons?

I am always on the lookout for useful methods to sample or partition study areas (usually in the form of raster datasets) into smaller units. Recently, I read an ESRI blog post about a new tool for ...
53
votes
9answers
131k views

Why does GPS positioning require four satellites?

I have a question on the GPS positioning algorithm. In all books I've read for 3D positioning we need four satellites, and I don't understand why. We need to calculate three variables: x, y, z. We ...
53
votes
13answers
19k views

Seeking QGIS tutorials and web resources?

I wish to familiarize myself with the capabilities of QGIS up to and beyond QGIS version 3.0. Can you recommend some good web resources and tutorials that would show me QGIS' capabilities? I am ...
53
votes
4answers
60k views

Which character encoding is used by the DBF file in shapefiles?

Which character-encoding is used by the dbf-file in shapefiles? It seems it is handled different, based on the program and the local encoding-settings of the machine. Which encoding is 'right' - ...
53
votes
2answers
97k views

Selecting features within Polygon from another layer using QGIS?

I'm using QGIS 1.8 with a PostGIS database and I have three PostGIS-layers in QGIS a lines layer, a points layer and a polygon layer. What I'm trying to do is to select a polygon in the polygon layer ...
53
votes
11answers
108k views

Obtaining up-to-date list of US ZIP Codes with Latitude and Longitude Geocodes? [closed]

NOTE: This began as a question on Stack Overflow, which has subsequently been closed. I also noticed a similar question about Most Up-To-Date Source for US Zip Code Boundaries, but I believe this ...
53
votes
7answers
129k views

Calculating Latitude/Longitude X miles from point?

I am wanting to find a latitude and longitude point given a bearing, a distance, and a starting latitude and longitude. This appears to be the opposite of this question (Distance between lat/long ...
52
votes
9answers
62k views

Choosing colour-ramp to use for elevation?

This is maybe rather subjective as it concerns style, but I would like to have a few decent colour ramps for my DEM when it is layed over my hill-shading. I have created the Swiss hillshade model as ...
52
votes
12answers
84k views

Seeking administrative boundaries for various countries?

After learning about the US Census's TIGERLines datasets I've working with the following layers, from the USA data Country boundaries State boundaries County boundaries City boundaries ZipCode/...
52
votes
5answers
3k views

How to calculate most efficient route passing through all the houses in the world?

I'm new to GIS. I need some help in determining the best or most efficient route, using a flying sleigh, through all the houses in the world. One of my coworkers told me that this site would be the ...
52
votes
3answers
22k views

Smoothing polygons in contour map?

Here is a contour map for which all the polygons of levels are available. Let ask how to smooth the polygons keeping all vertices preserved in their exact locations? Indeed the contour is made on ...
51
votes
3answers
43k views

How can I get a shapefile from a postgis query?

My data is in a PostGIS database. I would like to generate a shapefile from a query. How can I do that?
51
votes
6answers
16k views

How can I switch line direction in QGIS?

Something that is hopefully pretty easy. I would like to be able to swap the direction of a polyline/line in QGIS. I made a custom tool to do this in MapInfo a couple of years ago, however I can't ...
51
votes
3answers
55k views

Uninstalling QGIS that was installed using OSGeo

I installed QGIS using OSGEO4W, and would love to know how to uninstall it, because when I go to "Control Panel > Programs > Uninstall" the program does not appear in the list of installed programs. ...
51
votes
4answers
26k views

What is the going rate for GIS freelancers?

There appears to be very little information available about competitive hourly rates for GIS freelancers. Additionally, GIS freelancers never post rates on their websites. Upwork has some ...
51
votes
3answers
51k views

Choosing between QGIS and GRASS for simple thematic maps with different layers

I was working with GIS and remote sensing in a university and professional environment some ten years ago (ArcInfo etc), so I have some experience even though somewhat outdated. Now I am looking for ...
50
votes
7answers
115k views

Getting list of coordinates for points in layer using QGIS?

I've got a layer in QGIS that is comprised of points. Its attribute table doesn't have (show) the corresponding x and y coordinates for each point. Is there a way for me to extract a list of ...
50
votes
5answers
36k views

Bypassing 10 character limit of field name in shapefiles?

I'm exporting geometry with attached text attributes from oracle database to esri shapefile format (.shp) with Java and Geotools library. Attribute columns in our database have names with more than ...

15 30 50 per page