All Questions

Filter by
Sorted by
Tagged with
65 votes
3 answers
91k 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 ...
user avatar
141 votes
5 answers
28k views

Accessing ArcObjects from Python

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?
user avatar
  • 27.5k
83 votes
31 answers
62k views

How to Start Web Mapping?

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 ...
105 votes
16 answers
66k views

Identifying Coordinate System of Shapefile when Unknown?

I have a Shapefile but its coordinate system is Unknown, and there is no *.prj file. How can I identify it now?
user avatar
  • 3,596
565 votes
7 answers
487k views

Measuring accuracy of latitude and longitude?

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 ...
user avatar
  • 5,777
7 votes
1 answer
1k views

Use QGIS expressions to create geometries: difference between geometry generator and geometry by expression

QGIS has a powerful expression machine that can be used (between other things) to create new geometries, based on existing layers. Basically, there are two options: Geometry generator and Geometry by ...
user avatar
  • 40k
180 votes
7 answers
210k views

Installing File Geodatabase (*.gdb) support in QGIS

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 ...
user avatar
  • 9,196
49 votes
7 answers
46k views

OpenLayers low resolution and/or shifts in QGIS print composer?

I'm having trouble with the OpenLayers Plugin of Qgis and the map composer: If I create an OSM-background layer and if I want to export this, the OSM-Layer looks perfectly all right in the normal ...
user avatar
  • 2,161
10 votes
3 answers
6k views

Assigning point IDs to respective start and end attributes of polyline using Arc Hydro with ArcMap

I have two shapefiles, Point and Polyline. I'm trying to populate my polyline layer with the point data ID (systemID) where the lines start to where they end; eg. create two columns (from and to). The ...
user avatar
  • 159
39 votes
12 answers
69k views

Exporting feature class into multiple feature classes based on field values using ArcGIS Desktop?

I have a feature class with over 2,000 features, and I need to make them all individual feature classes based on a field. Is there a way to do this?
user avatar
  • 393
12 votes
1 answer
3k views

Auto incrementing field based on groups within feature class?

I am needing to auto increment a field based on groups within a feature class. I have 8 plots within a given polygon and I need to assign them an ID from 1-8 for each set of plots within each polygon. ...
user avatar
  • 123
38 votes
3 answers
12k views

Using QGIS Processing algorithms from PyQGIS standalone scripts (outside of GUI)

I am writing a script which must work outside of QGIS GUI. I call some API functions from qgis.core but I would like to use the processing plugin. I am able to import processing with sys.path.append() ...
user avatar
  • 634
260 votes
11 answers
145k views

Difference between projection and datum?

What's the difference between a projection and a datum?
user avatar
  • 9,311
21 votes
1 answer
5k views

Using customized Coordinate System in ArcGIS Desktop?

I don't know so much about coordinate systems... In my office we use to deal with spatial data coming from archaeological sites. Each site has its own x-y-z coordinate system (GCS). Three simple ...
user avatar
  • 451
196 votes
6 answers
485k views

Adding Basemaps from Google or Bing in QGIS

ArcGIS Desktop has the option of using basemaps from ArcGIS Online. Does QGIS have any such options?
user avatar
  • 3,191
35 votes
4 answers
24k views

More Efficient Spatial join in Python without QGIS, ArcGIS, PostGIS, etc

I'm attempting to do a spatial join much like the example here: Is there a python option to "join attributes by location"?. However, that approach seems really inefficient / slow. Even ...
user avatar
51 votes
3 answers
65k views

Reprojecting vector layer in QGIS

I have a series of layers of lines (shapefiles) in My Project. The CRS of some are different and to merge them they all must have same CRS. When I use Processing > Toolbox > Qgis_algorithims >...
user avatar
  • 511
108 votes
8 answers
261k views

Calculating polygon areas in shapefile using QGIS

How do I calculate areas of an area shapefile in square meters (m²) or in acres (ha)? I didn't find that functionality in the Vector Tools.
user avatar
  • 2,161
25 votes
2 answers
14k views

Displaying world country shapefiles centered on Pacific Ocean using Robinson or Miller Cylindrical projection in QGIS?

I wish to display a map in QGIS (world country shapefiles) showing all countries but centered on the Pacific area. I am not familiar with Proj4, so is there any way this can be done in QGIS?
user avatar
  • 271
29 votes
5 answers
33k views

Enabling CORS in GeoServer (jetty)?

I hope somebody has already figured this one out. I just installed Geoserver 2.9 on a vanilla Ubuntu 16.04 distro. The Geoserver 2.8 method of enabling CORS with the shanbe.hezoun class does no longer ...
user avatar
35 votes
7 answers
45k views

Fixing geometry validity errors in QGIS 2

I am working on ownership data at a US county level. I have one shapefile per county that contains thousands of tax parcels. I need to dissolve the polygons representing parcels owned by the same ...
user avatar
  • 915
36 votes
8 answers
44k views

Georeferencing vector layer with control points using QGIS?

I have a non-georeferenced vector layer that I need to be georeferenced. With raster layers the task is easy and straightforward, but I have no idea what should I do with my vector layer. I have a few ...
user avatar
  • 461
9 votes
1 answer
1k views

Changing shapefiles from geographic (WGS84) to projected (EPSG:2263) coordinate system using QGIS

I am trying to calculate service area polygons using the QNEAT3 plug in tool for a project I am doing. However, I got an error before these polygons could be created. 2021-01-04T08:03:38 CRITICAL ...
user avatar
  • 173
10 votes
4 answers
10k views

Determining bare earth DEM from unclassified LAS file?

I have data in LAS format with RGB values created from aerial photogrammetry using a UAV. I am trying to find a solution to extract the bare earth DEM from the point cloud. I have tried SAGA, ...
user avatar
  • 101
41 votes
1 answer
8k views

Coordinate system for accurately calculating areas of polygons that cross UTM Zones?

I have multiple polygons, all located offshore around the UK. I am trying to calculate the areas of these polygons in square kilometres, without splitting them by UTM zone. Is it possible to do this ...
user avatar
  • 797
58 votes
7 answers
145k 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 ...
user avatar
21 votes
3 answers
17k views

Importing qgis.core when writing standalone PyQGIS script

I am trying to write a standalone Python script in windows 7 that uses qgis.core and various other qgis libraries. I have found an old question on this subject at Writing standalone Python scripts ...
user avatar
  • 399
24 votes
5 answers
25k views

Including variable in where clause of arcpy.Select_analysis()?

I am trying to loop through a shapefile, selecting each feature in turn and copying it to a temporary shapefile to by included in a union analysis. I'm using a cursor to find the ID name for each ...
user avatar
  • 1,062
219 votes
4 answers
218k views

EPSG 3857 or 4326 for GoogleMaps, OpenStreetMap and Leaflet

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 ...
user avatar
  • 2,303
37 votes
2 answers
30k views

Learning ArcPy?

Where can I start to learn ArcPy?
141 votes
9 answers
230k views

Algorithm for offsetting a latitude/longitude by some amount of meters

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 ...
user avatar
  • 1,703
54 votes
7 answers
135k 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 ...
user avatar
  • 2,977
29 votes
2 answers
20k views

Understanding Join Attributes by Location in QGIS?

I wonder if there is somewhere an explanation for the parameters that can be set when running the Algorithm "Join Attributes by Location" in QGIS 2.18. I had a look here: Documentation QGIS Testing |...
user avatar
  • 3,017
32 votes
7 answers
39k views

Joining multiple records to single feature using QGIS

I'm trying to create a join/relate in QGIS where I have a shapefile of buildings and to that I would like to join a non-spatial table (.csv-file) containing people who work in each building. So I have ...
user avatar
  • 321
9 votes
2 answers
1k views

Computing dominant area in polygon using ArcGIS Desktop?

First, I have a shapefile consisting of square grids and each grid has an ID. Second, I have a shapefile consisting of different zones (with IDs). A grid ID in the first shapefile can contain many ...
user avatar
  • 369
105 votes
13 answers
171k views

Installing GDAL with Python on Windows

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. ...
34 votes
7 answers
58k views

Changing CSV layer attribute value from text to number in QGIS?

I read in a CSV file for linking to a .shp file. All the variables that are just numbers came in as text. How do I change the text variables to numeric in QGIS?
user avatar
22 votes
5 answers
19k views

Finding centrelines from polygons in QGIS

I was wondering if there is a way to create center lines from polygons in QGIS? I have a polygon layer, but ideally need the centerlines as a separate file.
user avatar
  • 2,397
84 votes
9 answers
173k views

Converting projected coordinates to lat/lon using Python

This site returns Point: X: -11705274.6374 Y: 4826473.6922 when you search with the first key value of 000090, as an example. I assume that this is a spatial reference. I am looking for instructions, ...
user avatar
  • 951
73 votes
7 answers
29k views

Creating regular polygon grid in PostGIS

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 Creating regular point grid inside polygon in PostGIS ...
user avatar
46 votes
12 answers
28k views

Map matching links and ideas? [closed]

I'm using OpenStreetMap and its vectorial road network and I'd like to implement a map matcher algorithm. Currently I'm able, for each GPS position, to retrieve the nearest road segment and ...
38 votes
7 answers
54k views

Performing Raster Reclassification in QGIS

Is there a way to perform a reclassify of a raster image in QGIS? In ArcGIS Desktop you can do that in Spatial analyst Tools→Reclass→Reclassify
user avatar
  • 3,326
116 votes
7 answers
55k views

Spatial clustering with PostGIS?

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 ...
user avatar
  • 6,618
135 votes
14 answers
62k views

What are Definition, Algorithms and Practical Solutions for Concave Hull?

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 (Wikipedia)...
user avatar
  • 6,554
46 votes
1 answer
32k views

Getting pixel value of GDAL raster under OGR point without NumPy?

I am working on a computational model of the abundance of wild pollinators across a landscape. The model itself is complete, and I am now struggling with a post-processing step. I have my GDAL ...
user avatar
  • 708
57 votes
11 answers
63k 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 ...
user avatar
  • 681
52 votes
8 answers
86k 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/...
67 votes
5 answers
114k views

Clipping raster with vector boundaries using QGIS

In 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 can I clip this ...
user avatar
  • 671
28 votes
11 answers
83k views

Extracting raster values at points using Open Source GIS?

How can I extract values from a raster by points? I prefer not in Arcgis. I prefer in Qgis or Mapwindow or other open source gis.
user avatar
  • 3,326
42 votes
5 answers
78k views

Splitting shapefile into separate files for each feature using QGIS or SAGA [closed]

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 Desktop - see ...
user avatar
  • 429

15 30 50 per page
1
2 3 4 5
383