Cartometric Blog

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Terminal one-liner to create shapefile from WKT using ogr2ogr

without comments

Fair warning, this is a Linux-themed solution. But I expect it could be ported to Windows without too much trouble.

Today I needed to create a shapefile with a single point geometry in it to use as an input for a random GIS utility executable, which required its input to be a an actual shapefile rather than an array of coordinate pairs, or even a single coordinate pair, or even separate x=/y= input parameters for a single coordinate pair. I already had the point coordinate I wanted to use, and I didn’t want to go to the trouble to make this shapefile! So I got to wondering if I could use ogr2ogr to render a simple shapefile from the terminal.

Fortunately, with the help of some utilities built in to my Ubuntu shell, I was able to come up with the following solution. This compound command 1) creates an empty file (dataset.csv), 2) pushes two features into it, and 3) uses ogr2ogr to translate the CSV into a shapefile projected accordingly–in this case, to EPSG:4326.

Here’s the full command. Note that a pair of ampersands (&&) are used to daisy-chain the individual steps together into a single instruction:

touch dataset.csv && printf "gid,WKT,some_value\n1,POINT(-82.048051 33.567181),Alpha\n2,POINT(-92.7774 35.9829),Beta\n" > dataset.csv && ogr2ogr -f "ESRI Shapefile" dataset.shp -dialect sqlite -sql "SELECT gid, GeomFromText(WKT), some_value FROM dataset" dataset.csv -a_srs EPSG:4326

Here’s a breakdown of what happens..

touch dataset.csv
  • Create a file (in the current directory) named “dataset.csv”

printf "gid,WKT,some_value\n1,POINT(-82.048051 33.567181),Alpha\n2,POINT(-92.7774 35.9829),Beta\n" > dataset.csv
  • Push a string through standard output (STDOUT) and INTO (>) the new file “dataset.csv”
  • The string imposes line breaks using the “\n” sequence and establishes a CSV type containing three lines
  • The three lines of content include: a column header, feature 1, and feature 2

ogr2ogr -f "ESRI Shapefile" dataset.shp -dialect sqlite -sql "SELECT gid, GeomFromText(WKT), some_value FROM dataset" dataset.csv -a_srs EPSG:4326
  • The ogr2ogr command exports a shapefile, “dataset.shp”
  • The input file, “dataset.csv” is included toward the end, along with the declaration of the source data’s CRS (EPSG:4326/WGS84)
  • ogr2ogr is instructed to use the “SQLITE” dialect of sql to pull data from the target dataset
  • The SQL command makes sure ogr2ogr knows to identify the WKT column as the source data’s geometry field

It runs pretty quickly, and does exactly what I wanted: Quickly crank out a shapefile if all I have is a point or a polygon or something, already in WKT format. I’m sure I’ll be using this again, so I wanted to document it here for easy reference later. Hopefully someone else finds it useful!

Written by elrobis

July 16th, 2020 at 5:04 pm

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