All Questions
896 questions
19
votes
1
answer
44k
views
Converting a polygon into a raster using R
I'm trying to convert a shapefile into a raster within R. My approach is to read in the raster as follows:
library(rgdal) # Loads SP package by default
demo <- readOGR('F:/data/', 'shapefile') # ...
- 16.3k
18
votes
2
answers
31k
views
Convert a spatial polygon object to data frame using R
My goal is to modify an existing shapefile by merging certain polygons.
After importing the shapefile and using the UnionSpatialPolygons command, I get the polygon outline that I want.
However, this ...
- 181
18
votes
9
answers
12k
views
how to overlay shapefile and raster?
I have a shapefile with polygons. And I have a global raster file. I want to overlay the shapefile's polygons onto the raster grid and calculate the mean raster value for each polygon.
How can I do ...
- 741
18
votes
2
answers
16k
views
Creating GeoJSON that works with D3
I'm simply trying to convert a .shp file to a geoJSON format using:
ogr2ogr -f geoJSON output.json input.shp
After executing the command nothing seems to be wrong. Here's an excerpt from the output....
- 541
17
votes
7
answers
9k
views
Free tool to simplify parcel shapefiles?
Is there any tool available which let's me run millions of parcel shapefiles and simplify them?
- 2,320
16
votes
1
answer
14k
views
Importing shapefile to PostGIS using Python and ogr
I just export a PostGIS Table to shp using this tips but I'm not able to import a shp to PostGIS using the same library(ogr). Any idea?
- 522
16
votes
4
answers
26k
views
Explaining difference between shx and shp files of shapefile?
I am searching for a more in depth explanation of the differences in shp and shx files to little avail. I mean beyond the 'shp contain geometry - shx contains an index of the geometry'.
The reason I ...
- 401
16
votes
4
answers
91k
views
Permission denied when creating shapefile
I'm having problems creating new shapefiles - in QGIS 2.14.20 any new fields I create and any associated data are not saved. I've now got the same problem in QGIS 3.0, but there I get a message ...
- 181
15
votes
7
answers
32k
views
Changing field length using QGIS
I have a shapefile I made in QGIS 1.7.4. One of the fields is a String of length 80. I'd like to make the field accept longer stings, but I can't figure out how to change its length.
How do I do this?
- 1,123
15
votes
5
answers
3k
views
Does Re-Projecting ShapeFile only update content of *.prj file?
If I wish to change the projection of some shapefiles from .. let's say NAD83 (4269) to WGS84 (4326) ... and by using some 3rd party app .... does this mean the .prj file is only updated .. and not ...
- 1,793
15
votes
5
answers
35k
views
Converting shapefile to WKT
I'm trying to convert a shapefile into the simple Well-Known-Text (WKT) format in the example below (from http://en.wikipedia.org/wiki/Well-known_text).
MULTIPOLYGON (((40 40, 20 45, 45 30, 40 40)),
((...
- 1,671
15
votes
4
answers
51k
views
Reading shapefile using C#? [closed]
I am new to ArcGIS and trying a few things..
I'm trying to read shapefile (which is supplied as an input) using C# and
I want to generate a PDF file which contains underlying metadata information (...
- 171
15
votes
6
answers
3k
views
Creating simple image from vector data
Can anyone suggest a quick (and preferably open source) way to create an image from a shapefile. For example, I have a shapefile containing parcel boundaries, I want to create a png file depicting ...
- 5,733
14
votes
3
answers
2k
views
How can I represent distance using the dashes or markers of a vector line?
I am a very basic user and dont know the lingo to get to the gist of my question so some background might help.
Ive volunteered to create a pre-incident planning system for my rural fire department. ...
- 141
14
votes
1
answer
43k
views
How to extract long and lat from geometry column in GeoPandas?
I read a shapefile with GeoPandas and I get a nice table with a column "geometry". This column contains shapely.geometry.polygon.Polygon or shapely.geometry.multipolygon.MultiPolygon object.
import ...
- 279
13
votes
4
answers
770
views
Are long lines in shapefiles to be considered geodesics or straight lines in the 2D latlong space?
Is there a definition on how lines connect vertices in the shapefile format?
In the simplest case, imagine a line with only 2 points, from 40,-118 to 40,-112 - that's somewhere random in the US - ...
- 275
13
votes
3
answers
44k
views
Extract Raster from Raster using Polygon shapefile in R
I am new to R and using the raster package. I have a problem extracting polygons from an existing raster file. If I use
extract(raster, poly_shape)
function on the raster it always creates a list ...
- 2,197
13
votes
5
answers
646
views
What in-depth spatial database systems tutorials exist? [closed]
Is there a good tutorial that explains in depth the internals of a GIS and a spatial database system such as PostGIS with examples and without any background assumption? I'm specifically looking for ...
- 141
13
votes
4
answers
5k
views
How to reproject spatial data using free libraries?
How can I use free libraries to transform spatial data?
For example,
I want to change the projection of a Shapefile within the code of my C# web application. How do I do that?
- 1,437
13
votes
3
answers
9k
views
Divide a complex shapefile into a grid
I have a decently detailed shapefile with polygon/multipolygon features (the file is about 500mb). It's actually a shapefile of the entire world, with the features representing coastlines. I need to ...
- 1,251
13
votes
8
answers
11k
views
Creating shapefile from current dataframe extents in layout view of ArcMap?
Where is the ArcGIS 10 tool for creating a shapefile from current dataframe extents in layout view?
Have looked around and the closet thing i can find is Toolbox's Grid/Strip Map Index tools under ...
- 2,059
13
votes
2
answers
21k
views
writeOGR with a spatialpolygon simplified by gSimplify
I'm using gSimplify (rgeos package) to simplify the geometries of a shapefile. The funcion works good, but now I can't write the output in a new shapefile.
I tried some ways:
writeOGR(simplyshape, ...
- 419
12
votes
3
answers
7k
views
Voronoi Diagram on a given polygon using QGIS
I am trying to create a Voronoi Diagram on a specific polygon, but there is some issue when dealing with edges.
Here is how I do it:
Preparing the points for Voronoi and the polygon for the diagram
...
- 365
12
votes
2
answers
11k
views
Determining if shapefile and raster overlap in Python using OGR/GDAL? [closed]
I am building a script in python using OGR/GDAL.
I have a set of shapefiles and a set of GeoTiff raster files.
I would like to have my script ignore shapefiles if they do not intersect with the ...
- 347
11
votes
1
answer
27k
views
Copy single feature into another feature class
I do a lot of editing, in this case areas. Sometimes I add an area to one shapefile, only to realise a bit later that it should have been in another.
Is there an easy way of copying only that ...
- 4,938
11
votes
3
answers
2k
views
Which data format typically displays fastest in ArcMap?
My organization is working on an application running on ArcGIS Engine. Previous versions of the application used primarily Shapefiles for displaying roads, parcels, buildings, etc.
Since I was ...
- 7,404
11
votes
2
answers
8k
views
How to convert GDB data to shapefiles without ArcGIS?
We've got some data (supposedly it's a simple collection of points--or at least that is all we need to extract) from a 3rd party in a GDB folder (I don't know how to tell what version) but we don't ...
- 211
11
votes
2
answers
1k
views
What's the batched Refactor Fields tool "field mapping" syntax in QGIS?
In QGIS, there is this nice tool "Refactor Fields" in the Processing Toolbox :
Using it on a single layer is fairly straightforward.
However, when you plan on using it in a batch mode, one can see ...
- 7,888
11
votes
4
answers
35k
views
Join CSV file to shapefile
I wanted to join a CSV file to a shapefile.
When I identified a field to facilitate the join, e.g.,
map <- spChFIDs(map, as.character(map$ID))
it returned
Error in spChFIDs(SP, x) : lengths ...
- 303
10
votes
6
answers
10k
views
How to add a projection to a Shapefile using open-source tools?
I have been given some shapefiles WITHOUT a projection. So I need to add the projection in order to display it on google map. I found the projection information I need at http://spatialreference.org/...
- 1,129
10
votes
6
answers
1k
views
Database versus Files for Solo Developer
I'm just getting started in GIS and am interested in using it to create maps of mountain biking trails in my area and nearby. I've been learning QGIS and have made enough progress to generate a decent ...
- 1,971
10
votes
6
answers
3k
views
How to programmatically check if the number of shapes = number of table records?
I have a handful of approximately 1000 shapefiles that are corrupted (see attached error message). The shapefiles were generated from eCognition Developer 8. There is a script tool that seems to ...
- 51.8k
10
votes
1
answer
9k
views
How to export multiple Shapefiles to one KML file in QGIS?
As the title says, is it possible to export multiple Shapefiles to one single KML in QGIS (Similar to "Map to KML" in ArcMAP)?
- 383
10
votes
4
answers
16k
views
Convert Polygon Feature Centroid to Points using Python
I would like to convert some polygon based shp files that have several polygon features into points for each feature that would essentially represent the centriod of each polygon feature. I know in ...
- 1,719
10
votes
1
answer
10k
views
Is it possible to change default encoding for QGIS?
I often transfer layers from Windows machine to Linux and vice versa and it causes me problems (incorrectly displayed labels and same with text in attribute table) when I use drag and drop to put ...
- 1,738
10
votes
3
answers
23k
views
How to get all the lat/long coords that define a shapefile
I have a Shapefile with several shapes inside it.
Using MapWindow I have been able to determine that the shape I need is the one with shapeId 19.
As you can probably tell I have very little ...
- 203
10
votes
2
answers
9k
views
Point (of a linestring) within Polygon using ogr and Python
I'm currently working on a project in which I need to build a topological network out of the geometry features I find in shapefiles.
So far using Ben Reilly's open source project I've managed to ...
- 466
9
votes
3
answers
16k
views
Dissolving shapefile but retain attribute fields using ArcGIS Desktop?
Is there any way to dissolve shapefile but keep attributes fields in the same time?
This is how I want to retain fields:
There are two fields I want to conserve in a shapefile. The first column is ...
- 141
9
votes
1
answer
13k
views
Exporting shapefile to KML with labels
In QGIS, When exporting my point shapefile to KML, points label are not visible in Google Earth Pro. I follow these steps:
In QGIS, my point shapefile has a name attribute
Right click on the shape ...
- 245
9
votes
2
answers
18k
views
Adding CRS to shapefile in GeoPandas
I am trying to add CRS to a shapefile that I am exporting:
shp1 = gpd.read_file(i[1], encoding='iso8859_7', crs_wkt='2100')
shp1.to_file(out, encoding='iso8859_7', crs_wkt='2100')
When I import it to ...
- 101
8
votes
1
answer
7k
views
Generate rectangular fishnet or vector (grid cells) shapefile in R?
I would like to create a polygon of 20 x 10 degree graticules from 180, -180 to 90, -90 degrees.
To do this in QGIS, I followed:
Vector creation tools > Create grid
[Grid extent: -180, 180, -90, 90]...
- 435
8
votes
1
answer
791
views
The longest straight line (L) within a polygon and the longest perpendicular line (T) to L
I'm mapping elongated glaciological features within QGIS 2.18.22 and I need to measure the longest straight line (L) and the longest perpendicular line (T) to L (as illustrated in the picture) within ...
- 81
8
votes
1
answer
25k
views
Creating shapefile from Excel file in QGIS?
I am using QGIS 2.6.1 and have worked in an Excel file database (which was actually converted from a Shapefile). I have managed to convert it as CSV file and load it into QGIS (displays data fine) but ...
- 81
8
votes
4
answers
11k
views
Seeking tool to convert GTFS (General Transit Feed Specification) to SHP / KML? [closed]
I need to convert GTFS (General Transit Feed Specification https://developers.google.com/transit/gtfs/reference), data into some GIS data format like ESRI Shapefile or KML or something else.
Do you ...
- 2,021
7
votes
1
answer
2k
views
Updating Lat/Longs and actual position of point shapefile using arcpy.UpdateCursor()?
I have a point shapefile with over 3000 points that are updated frequently, when they are updated they need to have their lat/longs changed which is entered into the attribute table.
When the lat/...
- 2,125
7
votes
4
answers
13k
views
How to convert SHP to GPX or to JSON?
I would like to convert the tree inventory shape files of London (Canada) into a GPX file and if possible into a JSON file. You can download the archive from their Open Data website. It contains the ...
- 1,521
7
votes
1
answer
20k
views
Why is my prj file not being read by QGIS?
I am using QGIS 1.8.0, and have been given a shapefile containing .shp, .prj, .shx, .dbf, however, qgis will not load the .prj file stating an invalid data source.
Altering the project properties>...
- 73
7
votes
5
answers
14k
views
Converting WKT to SHP?
I have a text file containing exactly this:
POLYGON ((6.2973716 48.98613 1772.1, ...many other Long Lat Altitude values ... ))
And only this. It seems to be just like a WKT geometry of a polygon. But ...
- 10.9k
7
votes
2
answers
8k
views
How to to validate geometries using ogr2ogr
I have been trying to dissolve a shapefile with more than 38000 rows. I used query as follows
ogr2ogr -f "ESRI Shapefile" dissolved.shp Barangays.shp -dialect sqlite -sql "select ST_union(Geometry),* ...
- 198
7
votes
3
answers
4k
views
Calculating area of vegetation in raster file?
How do I calculate area of several vegetation types in a raster (.img file type) image. They are color coded. Am using QGIS (1.8.0) and ERDAS 9.2.
- 79