All Questions
19,111
questions
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 ...
- 671
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?
- 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?
- 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 ...
- 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 ...
- 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 ...
- 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 ...
- 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 ...
- 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?
- 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. ...
- 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() ...
- 634
260
votes
11
answers
145k
views
Difference between projection and datum?
What's the difference between a projection and a datum?
- 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 ...
- 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?
- 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 ...
- 399
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 >...
- 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.
- 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?
- 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 ...
- 2,145
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 ...
- 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 ...
- 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 ...
- 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, ...
- 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 ...
- 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 ...
- 773
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 ...
- 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 ...
- 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 ...
- 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 ...
- 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 ...
- 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 |...
- 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 ...
- 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 ...
- 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?
- 957
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.
- 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, ...
- 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 ...
- 953
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
- 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 ...
- 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)...
- 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 ...
- 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 ...
- 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 ...
- 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.
- 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 ...
- 429