GIS Stack Exchange
GIS Stack Exchange

Most Popular

more tags
1500 questions
28
votes
5 answers

Seeking comprehensive list of latitude and longitude values for cities around world?

I'm developing an application that calculates the distance between cities using their respective Longitude and Latitude values. But the problem is where to get a comprehensive list of latitude and longitude values of these cities?
hello
  • 411
  • 1
  • 6
  • 10
28
votes
2 answers

What is the difference between != NULL and IS NOT NULL in QGIS filter expressions?

I have a shape layer with an attribute containing NULL values to which I would like to apply a filter for values different from NULL. Using the available GUI for such query construction, one would intuitively try "obj_art" != NULL Which means…
Jochen Schwarze
  • 14,605
  • 7
  • 49
  • 117
28
votes
4 answers

Seeking model builder for QGIS?

Like the ModelBuilder of ArcGIS Desktop to run simultaneous geoprocessing tools, is there any model builder available in QGIS?
SNT
  • 3,379
  • 11
  • 36
  • 49
28
votes
3 answers

Is it possible to get the EPSG value from an OSR SpatialReference class using the OGR Python API?

When reading a layer from a OGR PostGIS connection I can get the SpatialReference of the layer, but is it possible to get the EPSG value? Is there any documentation on this? For example: lyr = conn.GetLayerByName(tbl) # Where conn is OGR PG…
Tomas
  • 748
  • 1
  • 7
  • 16
28
votes
6 answers

How to efficiently access files with GDAL from an S3 bucket using VSIS3?

So, GDAL has recently added a new feature that allows random reading of S3 bucket files. I am looking to crop GDAL images from multiple tiles of an image without having to download the whole file. I've only seen very sparse documentation on how to…
Skylion
  • 529
  • 1
  • 6
  • 16
28
votes
5 answers

Converting MultiLinestring to Linestring with PostGIS

I have a multiline string and want to convert it to a linestring in order to use some functions that only work with linestrings. I used ST_Dump() and got a collection of my geometries. If I merge them back together, I still get the…
Antony
  • 925
  • 1
  • 11
  • 23
28
votes
3 answers

GIS Consulting - How to Get a Foot in the Door?

I currently work for a very large company as a GIS developer, and while I am happy in my position for the most part, I can't help but wonder what life as a GIS consultant (i.e. working for myself) would be like... I know there are many excellent GIS…
user890
  • 5,733
  • 1
  • 42
  • 71
28
votes
3 answers

Organizing GIS projects?

I have been struggling for quite a long time now with keeping my project files organized. What are your tips for keeping your datasets, images, shapefiles, etc.. organized?
relima
  • 2,810
  • 4
  • 26
  • 37
28
votes
6 answers

Creating polygon with extents of raster file in QGIS

I have a tiff image file and want to get a polygon with the extent of the tiff. Is there a direct way of doing this? Right now I have to convert the image to vector (with gdal_polygonize) and then dissolve the polygons.
vascobnunes
  • 5,570
  • 13
  • 49
  • 74
28
votes
2 answers

What is OSGeo4W?

I have been using GIS for a few years now (ArcGIS and MapInfo). But only when I have started using QGIS I come across OSGeo4W, as there is an option to download it on the QGIS website. I have tried looking it up online but everything is very…
T.O.6
  • 947
  • 2
  • 10
  • 16
28
votes
2 answers

Getting started with QGIS plugin development?

I wish to develop a simple plugin for QGIS, which will open some data, and perform some specific processing. I tried searching on the QGIS wiki, but only found this link : http://www.qgis.org/wiki/Writing_C++_Plugins which seems to be obsolete.…
Devdatta Tengshe
  • 41,311
  • 35
  • 139
  • 263
28
votes
3 answers

Creating conditional statement in QGIS Field Calculator

In QGIS 2.8 I have a large data set and I would like to search one field for any values over a certain amount (in this case 20) and if the value is larger than 20, I would like to return a value of 1 in another field, otherwise return a value of…
user35127
  • 399
  • 1
  • 3
  • 9
28
votes
3 answers

Is there a dissolve function in PostGIS other than st_union?

I'm looking for a function to dissolve shared boundaries between polygon features in a table. ST_UNION() almost does what I'm looking for, but it creates a multipolygon from all polygons in the layer regardless of whether they share a common…
underdark
  • 84,148
  • 21
  • 231
  • 413
28
votes
3 answers

Join spatial point data to polygons in R

I am trying to perform a spatial join between point data and polygon data. I have data that indicate the spatial coordinates of an event in my csv file A and have another file, shapefile B, that contains the boundaries of an area as…
ben_aaron
  • 383
  • 1
  • 3
  • 6
28
votes
6 answers

Good websites for map-lovers?

I often visit strange-maps, cool-maps, makingmaps and hipkiss.org. Do you know of other good websites for map-lovers?
julien
  • 10,186
  • 6
  • 55
  • 93
1 2 3
…
99 100