Boundless PostGIS Tutorial

The Boundless PostGIS workshop is an excellent introduction to PostGIS. It can be argued that it is dated, but I think the fundamentals are still very valid. However maintaining a free course is quite an overhead for any company. So I don’t blame them from taking it down, and no longer hosted it on the Boundless website.

However it was released under a creative commons license and the source is easily available on GitHub, and can be easily built.

You can find a hosted version on: GISforThought.com/projects/postgis_tutorial/

The data can be found in my previous post: GISforThought.com/postgis-tutorial-data/

PostGIS Tutorial Data

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The OpenGeo (now called Boundless) PostGIS tutorial has long been my recommendation for people just getting started with PostGIS. It provides a broad intro to PostGIS, great for users new to SQL.

Unfortunately they recently removed it from their website. The guide was a fairly old now, so I don’t blame them. But it was a great free resource.

I have created a version of the data used, which can be accesses at (choose the green Clone or download button and Download ZIP):

https://github.com/HeikkiVesanto/postgis_course_data

The data is also not 100% the same as the original. So some of the queries will have to be modified. Particularly the neighborhoods are different. So they may have slightly different names/boundaries/capitalization. So keep that in mind when creating your queries, and interpreting the results. But overall the data is pretty similar

The course has been compiled and can be found at: https://gisforthought.com/boundless-postgis-tutorial/

Copying Rasters in PostGIS

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I ran into a process where I wanted to create copies of rasters in PostgreSQL. While seemingly a simple process this took me a bit of work to figure out.

For my workflow I had three rasters, which all have the same size, and I want to load them into the same PostGIS table with three raster geometry columns. I don’t think this will work for different sized rasters since the rid’s will not match.

Three rasters:
raster1 raster2 raster3

Which I want to copy into:
merged_raster

First to create the merged raster table:

CREATE TABLE merged_raster
(
  rid serial NOT NULL,
  raster1 raster,
  raster2 raster,
  raster3 raster
);

CREATE TABLE merged_raster

(

rid serial NOT NULL,

raster1 raster,

raster2 raster,

raster3 raster

);

Then to add the rid’s. These are the id’s of the tiles that the raster was split into when loading. If your tile size is large enough then you may only have one.

INSERT INTO merged_raster(rid)
(SELECT rid FROM raster1);

1 2	INSERT INTO merged_raster(rid) (SELECT rid FROM raster1);

Then copying the actual data is straighforward (this assumes the raster column in the raster1 datasets is called rast):

UPDATE merged_raster m
SET raster1 = r.rast
FROM raster1 r
WHERE r.rid = m.rid;

UPDATE merged_raster m
SET raster2 = r.rast
FROM raster2 r
WHERE r.rid = m.rid;

UPDATE merged_raster m
SET raster3 = r.rast
FROM raster3 r
WHERE r.rid = m.rid;

UPDATE merged_raster m

SET raster1 = r.rast

FROM raster1 r

WHERE r.rid = m.rid;

UPDATE merged_raster m

SET raster2 = r.rast

FROM raster2 r

WHERE r.rid = m.rid;

UPDATE merged_raster m

SET raster3 = r.rast

FROM raster3 r

WHERE r.rid = m.rid;

Now I still have an issue that QGIS will not load these layers. It will always load the initial raster column no matter what is chosen.

Dublin Monopoly

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Dublin has an official Monopoly board in time for Christmas.

Not to be confused with the Irish Edition of Monopoly. Which consisted of locations in Dublin with the addition of Shannon Airport.

Buy at:

Irish Edition

Dublin version

Full screen map.

Check out: MappingDublin.com

Anaconda install with OSGeo4W

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I was coming across some errors when installing Anaconda, Miniconda specifically.

https://conda.io/miniconda.html

I think part of the reason is I have quite a few installs of Python due to OSGeo4W.

My error:

Fatal Python error: Py_Initialize: unable to load the file system codec
ModuleNotFoundError: No module named 'encodings'

Current thread 0x00002554 (most recent call first):

Fatal Python error: Py_Initialize: unable to load the file system codec

ModuleNotFoundError: No module named 'encodings'

Current thread 0x00002554 (most recent call first):

The solution:

Update the activate.bat file that is called when launching from the start menu. For me located in:

C:\ProgramData\Anaconda\Scripts

1	C:\ProgramData\Anaconda\Scripts

We need to add in the following to clear out and reset the python environment before launching anaconda:

@SET PYTHONPATH=
@SET PYTHONHOME=C:\ProgramData\Anaconda
@PATH C:\ProgramData\Anaconda;C:\ProgramData\Anaconda\Scripts;%PATH%

@SET PYTHONPATH=

@SET PYTHONHOME=C:\ProgramData\Anaconda

@PATH C:\ProgramData\Anaconda;C:\ProgramData\Anaconda\Scripts;%PATH%

So, editing the file from:

@REM Test first character and last character of %1 to see if first character is a "
@REM   but the last character isn't.
@REM This was a bug as described in https://github.com/ContinuumIO/menuinst/issues/60
@REM When Anaconda Prompt has the form
@REM   %windir%\system32\cmd.exe "/K" "C:\Users\builder\Miniconda3\Scripts\activate.bat" "C:\Users\builder\Miniconda3"
@REM Rather than the correct
@REM    %windir%\system32\cmd.exe /K ""C:\Users\builder\Miniconda3\Scripts\activate.bat" "C:\Users\builder\Miniconda3""
@REM this solution taken from https://stackoverflow.com/a/31359867
@set "_args1=%1"
@set _args1_first=%_args1:~0,1%
@set _args1_last=%_args1:~-1%
@set _args1_first=%_args1_first:"=+%
@set _args1_last=%_args1_last:"=+%
@set _args1=


@if "%_args1_first%"=="+" if NOT "%_args1_last%"=="+" (
    @CALL "%~dp0..\Library\bin\conda.bat" activate
    @GOTO :End
)

@CALL "%~dp0..\Library\bin\conda.bat" activate %*

:End
@set _args1_first=
@set _args1_last=

@REM Test first character and last character of %1 to see if first character is a "

@REM but the last character isn't.

@REM This was a bug as described in https://github.com/ContinuumIO/menuinst/issues/60

@REM When Anaconda Prompt has the form

@REM %windir%\system32\cmd.exe "/K" "C:\Users\builder\Miniconda3\Scripts\activate.bat" "C:\Users\builder\Miniconda3"

@REM Rather than the correct

@REM %windir%\system32\cmd.exe /K ""C:\Users\builder\Miniconda3\Scripts\activate.bat" "C:\Users\builder\Miniconda3""

@REM this solution taken from https://stackoverflow.com/a/31359867

@set "_args1=%1"

@set _args1_first=%_args1:~0,1%

@set _args1_last=%_args1:~-1%

@set _args1_first=%_args1_first:"=+%

@set _args1_last=%_args1_last:"=+%

@set _args1=

@if "%_args1_first%"=="+" if NOT "%_args1_last%"=="+" (

@CALL "%~dp0..\Library\bin\conda.bat" activate

@GOTO :End

)

@CALL "%~dp0..\Library\bin\conda.bat" activate %*

:End

@set _args1_first=

@set _args1_last=

To:

@REM Test first character and last character of %1 to see if first character is a "
@REM   but the last character isn't.
@REM This was a bug as described in https://github.com/ContinuumIO/menuinst/issues/60
@REM When Anaconda Prompt has the form
@REM   %windir%\system32\cmd.exe "/K" "C:\Users\builder\Miniconda3\Scripts\activate.bat" "C:\Users\builder\Miniconda3"
@REM Rather than the correct
@REM    %windir%\system32\cmd.exe /K ""C:\Users\builder\Miniconda3\Scripts\activate.bat" "C:\Users\builder\Miniconda3""
@REM this solution taken from https://stackoverflow.com/a/31359867
@set "_args1=%1"
@set _args1_first=%_args1:~0,1%
@set _args1_last=%_args1:~-1%
@set _args1_first=%_args1_first:"=+%
@set _args1_last=%_args1_last:"=+%
@set _args1=

@SET PYTHONPATH=
@SET PYTHONHOME=C:\ProgramData\Anaconda
@PATH C:\ProgramData\Anaconda;C:\ProgramData\Anaconda\Scripts;%PATH%

@if "%_args1_first%"=="+" if NOT "%_args1_last%"=="+" (
    @CALL "%~dp0..\Library\bin\conda.bat" activate
    @GOTO :End
)

@CALL "%~dp0..\Library\bin\conda.bat" activate %*

:End
@set _args1_first=
@set _args1_last=

@REM Test first character and last character of %1 to see if first character is a "

@REM but the last character isn't.

@REM This was a bug as described in https://github.com/ContinuumIO/menuinst/issues/60

@REM When Anaconda Prompt has the form

@REM %windir%\system32\cmd.exe "/K" "C:\Users\builder\Miniconda3\Scripts\activate.bat" "C:\Users\builder\Miniconda3"

@REM Rather than the correct

@REM %windir%\system32\cmd.exe /K ""C:\Users\builder\Miniconda3\Scripts\activate.bat" "C:\Users\builder\Miniconda3""

@REM this solution taken from https://stackoverflow.com/a/31359867

@set "_args1=%1"

@set _args1_first=%_args1:~0,1%

@set _args1_last=%_args1:~-1%

@set _args1_first=%_args1_first:"=+%

@set _args1_last=%_args1_last:"=+%

@set _args1=

@SET PYTHONPATH=

@SET PYTHONHOME=C:\ProgramData\Anaconda

@PATH C:\ProgramData\Anaconda;C:\ProgramData\Anaconda\Scripts;%PATH%

@if "%_args1_first%"=="+" if NOT "%_args1_last%"=="+" (

@CALL "%~dp0..\Library\bin\conda.bat" activate

@GOTO :End

)

@CALL "%~dp0..\Library\bin\conda.bat" activate %*

:End

@set _args1_first=

@set _args1_last=

Updating the paths as required.

This just clears out the python and windows environmental variables before launching, similar to what OSGeo4W does.

GIS for Thought

GIS, Mapping, and Remote Sensing

Boundless PostGIS Tutorial

PostGIS Tutorial Data

Copying Rasters in PostGIS

Dublin Monopoly

Anaconda install with OSGeo4W