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61
votes
3answers
76k 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 ...
132
votes
5answers
24k 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?
83
votes
28answers
55k 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 ...
94
votes
15answers
49k 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?
439
votes
7answers
373k 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 ...
158
votes
6answers
148k 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 ...
45
votes
7answers
39k 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 ...
33
votes
12answers
61k 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?
9
votes
3answers
5k views

Assigning point IDs to respective start and end attributes of polyline?

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 ...
16
votes
1answer
4k 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 ...
230
votes
11answers
123k views

Difference between projection and datum?

What's the difference between a projection and a datum?
29
votes
4answers
16k 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 ...
40
votes
1answer
6k 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 ...
18
votes
2answers
10k 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?
46
votes
7answers
106k 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 ...
21
votes
5answers
21k 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 ...
10
votes
4answers
7k 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, ...
37
votes
6answers
28k views

Learning ArcPy?

Where can I start to learn ArcPy?
30
votes
5answers
36k views

Fixing geometry validity errors in QGIS?

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 ...
18
votes
2answers
12k views

Problem with import qgis.core when writing a stand-alone PyQGIS script

I am trying to write a stand alone python script in windows 7 that uses qgis.core and various other qgis libraries. I have found an old question on this subject here: Writing standalone Python ...
105
votes
5answers
177k 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 ...
25
votes
6answers
31k 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) containing people who work in each building. So I have ...
165
votes
3answers
147k 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 ...
52
votes
14answers
81k 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/...
72
votes
4answers
153k views

Calculating polygon areas in QGIS?

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.
43
votes
3answers
55k 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/...
53
votes
13answers
18k 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 ...
91
votes
13answers
109k 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. ...
43
votes
13answers
24k 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 ...
116
votes
13answers
47k views

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

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 (...
47
votes
7answers
93k 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 ...
44
votes
1answer
23k 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 ...
29
votes
8answers
30k 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 ...
27
votes
6answers
43k 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?
16
votes
5answers
16k 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 ...
10
votes
1answer
1k 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. ...
133
votes
4answers
283k 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?
25
votes
7answers
36k views

Performing Raster Reclassification in QGIS?

Is there a way to perform a reclassify of a raster image in QGIS? In ArcGIS you can do that in Spatial analyst Tools→Reclass→Reclassify Any ideas?
24
votes
1answer
25k views

Understanding QGIS buffer tool units?

I have been trying to figure this out for a couple weeks now and have had no luck getting the buffer tool to accept anything but degrees as units of measure. I have found lots of stuff saying the ...
97
votes
7answers
43k 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 ...
60
votes
5answers
20k 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 How to create regular point grid inside a polygon in ...
38
votes
6answers
19k views

Shapefile PRJ to PostGIS SRID lookup table?

I was wondering if there is such a thing as an shapefile PRJ to PostGIS SRID lookup table? Something that can translate the most standard shapefile PRJ definitions into the likely SRID. When using ...
51
votes
10answers
52k views

Removing small spaces (slivers) between polygons? [closed]

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. ...
57
votes
4answers
75k 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 ...
17
votes
5answers
12k views

Using SRTM Global DEM for Slope calculation?

I have downloaded SRTM GDEM (~90 km resolution). I am using ArcGIS 10. I have tried to use spatial analyst to compute for slope. However, I can not compute for the slope. The output values has ...
100
votes
6answers
156k views

Differences between DEM, DSM and DTM?

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 ...
81
votes
3answers
184k views

Merging multiple vector layers to one layer using QGIS?

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 ...
18
votes
4answers
13k views

Finding centrelines from polygons in QGIS?

I was wondering if there is a way to create centre lines from polygons in QGIS? I have a polygon layer, but ideally need the centrelines as a separate file.
17
votes
3answers
4k views

Import error for qgis.core when running OSGeo4w shell script

I've been trying, along with this post, to run a script in OSGeo4w Shell, outside of QGIS. But I get the following error: ImportError: No module named qgis.core I have also read the following ...
37
votes
1answer
21k views

Defining new custom projections in QGIS?

I'm trying to define a projection in QGIS. I want to add North America Albers Equal Area Conic. From the spatialreference site I copied the proj4 line: +proj=aea +lat_1=20 +lat_2=60 +lat_0=40 +lon_0=-...

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