Tag Archives: GIS

How to make a PostGIS TIGER Geocoder in Less than 5 Days

GeocoderWorking

It doesn’t look like much, but this image represents success!

I have been through 5 days of frustration wading through tutorials for how to make a Tiger geocoder in PostGIS.  My complaints, in a nutshell, are that every tutorial is either non-linear or assumes you already know what you’re doing… or both.  If I knew what I was doing, I wouldn’t need a tutorial.  And your notes on how you made it work are lovely, if only I could figure out what part of the process they pertain to.  Enough griping.  Here’s how I finally got this thing to work.

Note: I’m on Windows 10, PostGRESql 10, PostGIS 2.4.0 bundle.  This tutorial draws from many existing tutorials including postgis.net and this one with additional help from Alex Mandel.

What is a Tiger Geocoder?

Let’s start by breaking this down.  A geocoder is a tool composed of a set of reference data that you can use to estimate a geographic coordinate for any given address.  Tiger, in this case, does not refer to a large endangered cat, but rather the US Census’ TIGER spatial files.  This is the reference data we will use.  The process we’re about to embark on should make assembling this data easy by using tools that will help us download the data and put it into a PostGIS database.

Install Software & Prep Folders

You will need to install:

  1. postgreSQL 10 – the database program that’s going to make all of this work
    1. The installer should walk you through installation options.  Write down the port (keeping the default is fine) and password you choose.  Pick a password you like to type because it comes up a lot.
  2. PostGIS 2.4.x bundle – PostGIS makes postgreSQL have spatial capabilities (much like a super power) and install the bundle option because it comes with things you’ll need, saving a few steps
    1. Make sure you’ve installed PostGRESql first
    2. The installer should walk you through the installation options.
  3. wget 1.19.1 (or a relatively recent version) – this is a tool that the geocoder scripts will need to download files from the census
    1. Save the .zip option to your computer.
    2. Unzip it in your C:/ drive so it’s easy to access later.  Remember where you put it because you’ll need the path later.
  4. 7zip – this is an open source file unzipping tool that the scripts will use to unzip the files they download from the Census website.

You will need to create a folder on your computer to be your “staging folder”.  This is where the scripts we’ll run later will save the files they need to download.

  1. Make a folder called “gisdata” in a place where you have write permissions and can find it later.  For example: C:\gisdata
  2. Inside your gisdata folder, make another folder called “temp”. For example: C:\gisdata\temp

Make a Database

We need to make an empty database to put our files into.

Open PGAdmin 4.  This is the graphical user interface for postgreSQL that should have installed with the postgreSQL files.

If PGAdmin 4 doesn’t start or gives an error, you may need to start the service that makes it run.  In the Windows search bar, search “services”.  In the Services window, right click postgresql-x64-10 and choose “start”.

In the browser panel on the left side of the pgAdmin 4 window, click the + to expand Servers and PostgreSQL 10.  When it asks for your password, give it the password you wrote down during the installation process.

Right click on PostgreSQL 10 -> Create -> Database

In the Database name field, give it a name with lowercase letters.  I named mine geocoder.  Leave the owner drop-down on postgres.  Click Save.

Expand the Databases entry in the Browser panel to see your new database in the list.

Enable Extensions

Right now, our database is just a regular database without spatial functions.  We need to enable the PostGIS extension and the extensions that help us geocode.

Open the Query Tool: in the Tools menu at the top of the screen, select “Query Tool”.  The top section of the query tool is where you type SQL commands.  Underneath this is where the results of your queries are displayed.

Enable the PostGIS extension to give the database spatial capabilities by copying and pasting this code into the query tool and clicking the run button (it looks like a lightning bolt… why?  I don’t know.):

CREATE EXTENSION postgis;

The next three lines enable extensions that help with the geocoding process (run them one at a time):

CREATE EXTENSION fuzzystrmatch;
CREATE EXTENSION postgis_tiger_geocoder;
CREATE EXTENSION address_standardizer;

Let’s make sure the extensions loaded correctly. This line of code should take the address (in between the parentheses and single quotes) and break it down into it’s components (create a “normalized address”):

SELECT na.address, na.streetname,na.streettypeabbrev, na.zip
	FROM normalize_address('1 Devonshire Place, Boston, MA 02109') AS na;

The output should look something like this:

 address | streetname | streettypeabbrev |  zip
---------+------------+------------------+-------
       1 | Devonshire | Pl               | 02109

Edit the loader tables

The scripts we’re going to run (in a few steps from now) will need some information to run correctly.  The place they look for this information is a set of two tables that have been added to your database by the extensions we just enabled.

In the browser panel (on the left side of the window), expand your geocoder database, then the schemas list, the tiger list, and finally the Tables list.  Make sure you’re looking at the tables list inside of the the tiger list… each schema gets to have it’s own list of tables.

Right click on the loader_platform table, and select “View/Edit Data”, and then “All Rows”.  Now we can edit one of the entries to tell the scripts where to look for certain files and folders.

One row of the table has “windows” in the os (operating system) column.  In that row, double click the cell in the declare_sect column to open up a window that will let you edit the text.  For each line, you’ll need to make sure you type the path to the folder or file needed.  This is what mine looks like after editing:

set TMPDIR=C:\gisdata\temp
set UNZIPTOOL="C:\Program Files\7-Zip\7z.exe"
set WGETTOOL="C:\wget-1.19.1-win64\wget.exe"
set PGBIN=C:\Program Files\PostgreSQL\10\bin\
set PGPORT=5432
set PGHOST=localhost
set PGUSER=postgres
set PGPASSWORD=Password123
set PGDATABASE=geocoder
set PSQL="C:\Program Files\PostgreSQL\10\bin\psql.exe"
set SHP2PGSQL="C:\Program Files\PostgreSQL\10\bin\shp2pgsql.exe"
cd C:\gisdata

(No, that’s not my actual password.)  Note that some of the paths might be correct and others will not be, so check them all.  When you’re done, click Save and then close the table with the x button in the upper right corner (side note: I find the pgAdmin 4 interface to be rather unintuitive).  If it asks you to save your table, tell it yes.

Now open the loader_variables table.  Change the staging_folder to your chosen staging folder.  I hard-coded mine into the last table because it the scripts didn’t seem to be recognizing entries in this table, but change it anyway just to be sure.  Again, save and exit.

Make & Run the Scripts

Add postgreSQL path to Windows

Before we can use postgreSQL in the command line (sorry to spring that on you… deep breaths… we’ll work through this together), we need to make sure Windows knows about postgreSQL.

For Windows 7, this Stack Overflow post should help.  For Windows 8 and 10, try this one.

Make the Nation Scripts

Next, we are going to run a line of code that will automatically generate a script.  We’ll run that script to automatically download data from the Census and place it into your database.  (Yes, we are going to run code that makes bigger code that downloads data.)

Open a command line terminal (on Windows, search “cmd” in the search box and select the Command Prompt).  Copy and paste this line of code into your terminal window, changing the path to your staging folder (but keep the file name at the end), then hit enter to run the code:

psql -U postgres -c "SELECT Loader_Generate_Nation_Script('windows')" -d geocoder -tA > C:/gisdata/nation_script_load.bat

(Quick note about what this code does… “-U postgres” tells the command that the user name for the database we want to work with is “postgres”. “-d geocoder” tells it that the name of the database to use is “geocoder”. “SELECT Loader_Generate_Nation_Script” is a function that postGIS can use to make the script we’re going to need. The ‘windows’ argument actually tells it to read the line in the loader_platform table we edited earlier.)

The terminal will probably return this line:

Password for user postgres:

Type in your password, although it won’t show anything on the screen as you type, and hit enter.  A new prompt (the path for the folder you’re in and a >) will appear when it’s finished.  Your staging folder should now have a files called nation_script_load.bat  This new file is a batch file containing a series of commands for the computer to run that will download files from the Census’ website, unzip them, and add them to your database automatically.

Run the Nation Script

Running your new batch script in Windows, this is fairly straight forward (seriously, one step had to be, right?).

First, if you’re not already in the directory for your staging folder, change directories by running this command in the command line (How do you tell?  The command prompt shows the directory you’re in):

cd C:/gisdata

Now your command prompt should say C:/gisdata >

To run the script, in the command line, type

nation_script_load.bat

and hit enter to run your .bat file.  You will see a series of code run across your terminal window and it may open a 7zip dialog as it unzips files.  This could take a little while.

When it’s done, you should have a tiger_data schema with tables called county_all and state_all.  You can check to make sure the tables have data by running these lines in the pgAdmin 4 Query Tool:

Check the county_all Table:

SELECT count(*) FROM tiger_data.county_all;

Expected Results:

count
-------
 3233
(1 row)

Check the state_all table:

SELECT count(*) FROM tiger_data.state_all;

Expected Results:

 count
-------
 56
(1 row)

Make & Run the State Script

The process of making and running the state script are very similar to what we just did for the national script.  This script makes the tables for a state (or multiple states) that you specify.

In the command line, run this code to generate the scripts for California:

psql -U postgres -c "SELECT Loader_Generate_Script(ARRAY['CA'], 'windows')" -d geocoder -tA > C:/gisdata/ca_script_load.bat

Note that if you want additional states, add them to the bracketed list separated by commas.  For example, to download California and Nevada, you would run:

psql -U postgres -c "SELECT Loader_Generate_Script(ARRAY['CA', 'NV'], 'windows')" -d geocoder -tA > C:/gisdata/ca_nv_script_load.bat

Change directories back to your staging folder if needed by running this command in the command line:

cd C:/gisdata

Run the script by entering the name of the file into the command prompt:

ca_script_load.bat

The state script is going to take a while to load. It downloads many, many files. So go get a cup of coffee/tea/hot chocolate and a cookie while you wait.

Finally, we need to do some analyze all of the tiger data and update the stats for each table (reference). In the pgAdmin 4 query builder, run each of these lines separately:

SELECT install_missing_indexes();
vacuum analyze verbose tiger.addr;
vacuum analyze verbose tiger.edges;
vacuum analyze verbose tiger.faces;
vacuum analyze verbose tiger.featnames;
vacuum analyze verbose tiger.place;
vacuum analyze verbose tiger.cousub;
vacuum analyze verbose tiger.county;
vacuum analyze verbose tiger.state;
vacuum analyze verbose tiger.zip_lookup_base;
vacuum analyze verbose tiger.zip_state;
vacuum analyze verbose tiger.zip_state_loc;

Try it out

I know, it doesn’t seem like we’ve got a lot to show for all that work.  If you look in the tables for your Tiger schemas, you might notice that there’s more of them, but let’s get some concrete results.

Run this code in the pgAdmin 4 Query Builder to return a coordinate for an address in WKT (well known text).  Change the address to one in the state you’ve downloaded.  (More testing option here.)

SELECT g.rating, ST_AsText(ST_SnapToGrid(g.geomout,0.00001)) As wktlonlat,
(addy).address As stno, (addy).streetname As street,
(addy).streettypeabbrev As styp, (addy).location As city, (addy).stateabbrev As st,(addy).zip
FROM geocode('424 3rd St, Davis, CA 95616',1) As g;

It should return:

rating |          wktlonlat          | stno | street | styp | city    | st   | zip
0      | 'POINT(-121.74334 38.5441)' | 424  | '3rd'  | 'St' | 'Davis' | 'CA' | '95616'

(That’s the address for the Davis, CA downtown post office, in case you were wondering.)

You Did It!

You did it! I sincerely hope that at this point you have a geocoder that’s ready to use. Next up, I need to figure out how to geocode a bunch of addresses. More on that soon!

 

 

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ArcGIS Tabulate Area Error

Several times I’ve run into an error trying to run the Tabulate Area (Spatial Analyst) tool in ArcGIS.  [I know, I know… I’m more of an open source person, but you gotta use what they’ll let you have at work.]  The error code it gives is “Error 999999 : Error executing function.”  Great.  Cuz that’s helpful.  Here are some things to check.

  1. Did you put the right layers into each input field or should the be switched?  The order matters.  The one with “zone” in the description needs to have the shapefile or raster that defines the zones you want to use.
  2. Does the attribute information you are trying to use have spaces (or special characters like commas)?  Yeah, that doesn’t work.

Now, I don’t promise that one of these is going to solve your problem, but it’s at least something to look into, which Arc doesn’t give you.  I hope someone finds this helpful.  It was intended more as a note for me, since I’ve run into and troubleshot this problem more than once this year not remembering the solution.  That’s what blogs are for!


Aerial Photography: Coal Oil Point Reserve

Recently presented with the opportunity to submit a photograph to an ecological photo contest on campus, I’ve been working on cleaning up some of my recent balloon and kite aerial photography flights.  This photo was taken with my hot air balloon rig, which is now retired due to safety concerns, a few years ago at Sands Beach at Coal Oil Point Reserve near Santa Barbara.  The site is one of the University of California’s Natural Reserves.  I’ve stitched a bunch of photos together using Hugin, then cropped the scene down to a rectangle so it would be more pleasing to the audience.  The jagged edges of the stitched scene would probably be confusing to many unfamiliar with the process.  The black squares in the image are targets that I made to help georeference the scene, something that has proven to be more difficult than most GIS analysts would suspect.


Comic: Raster vs. Vector

Who among us has NOT had one of these moments?

For all you fellow GIS geeks, this is for you!  I drew this comic sketch a few years ago after a student told me that they were confused for an entire lecture because they swore the professor was talking about “raptors” and they weren’t sure what dinosaurs had to do with GIS.

Over the years I’ve drawn many silly little comics, some of them with no plots at all.  I think I’ll post one every now and then just for fun.  I hope you enjoy them.