Loading data into PostGIS

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This page is now getting a little more attention and organization.

Refer to "PostGIS in Action" (Obe and Hsu) Chapter 7

EPSG codes that I regularly use

  • EPSG:2913: NAD83(HARN) / Oregon North (ft)
  • EPSG:2914: NAD83(HARN) / Oregon South (ft)
  • EPSG:32026: NAD27 / Oregon North
  • EPSG:32027: NAD27 / Oregon South
  • EPSG:2992: Oregon Lambert (ft)
  • EPSG:2994: NAD83(HARN) / Oregon Lambert (ft)

See http://spatialreference.org

Loading shapefiles

First method: Loading shapefiles with shp2pgsql

Use the shp2pgsql command to create and load the table and then manually define the projection. Example: 

shp2pgsql lowerclack_subbasins.shp | psql -U postgres -d crbc_spatial

The shp2pgsql command appears to ignore the PRJ file that defines projection, so I manually enter a command to define the projection like this: 

echo "SELECT UpdateGeometrySRID('lowerclack_subbasins', 'the_geom', 2992);" | psql -U postgres -d crbc_spatial

There is also a plugin called shp2pgsql-gui included with the PostGIS source code for pgAdmin III that lets you load shapefiles directly from the pgAdmin tool. This looks elegant but I have not tested it yet.

Second method: Loading almost any data with ogr2ogr

I have information about using ogr2ogr to load GPX data into PostGIS on the GPX page.

Using 'ogr2ogr is convenient because you can load the data and reproject it in one step. Note source and destination are reversed in this command. Also very convenient because you can load any data that ogr2ogr knows about, do ogr2ogr --formats for the list. 

# Define desired projection using EPSG code, this one is Web Mercator.
PRJ="EPSG:900913"
# Define the source and destination fields
SRC=lowerclack_subbasins_merge.shp
DST='PG:"user=postgres dbname=crbc_spatial"'
# Do the work
ogr2ogr -t_srs $PRJ -f PostgreSQL $DST $SRC -lco GEOMETRY_NAME=the_geom

Do note the order is "destination source" not "source destination"

For Mapping Vietnam I want to load data from GIS Data Depot into PostGIS. At the moment I only want to do this so I have some data for testing. Later on I might even want these layers in a map.

The downloaded data are in ESRI "E00" format and have been compressed. 

# Uncompress all downloaded files
for file in *.E00.GZ; do gunzip $file; done

# put the data into "Web Mercator" projection
PRJ="EPSG:900913"
DB=vietnam

# The original files were coverages, so I have to know something about
# what I want to transfer. For example for this file I want only PAL
ogrinfo PPPOLY.E00
1: ARC (Line String)
2: CNT (Point)
3: LAB (Point)
4: PAL (Polygon) This is the one I want.

ogr2ogr -t_srs $PRJ -f PostgreSQL \
PG:"user=postgres dbname=$DB" \
PPPOLY.E00 PAL \
-lco GEOMETRY_NAME=the_geom -nln political_boundaries

Broken shapefiles

First off, if you have access to ArcGIS, run your shapefiles through the "Repair Geometry" tool to repair or remove broken features.

Secondly, apparently it is common for shapefiles to have columns that exceed the constraints defined in their DBF fork. Use PRECISION=NO to force them to load.

Thirdly, use 'skipfailures' to drop features that are wrong, for example in multilinestring format in a linestring shapefile. 

ogr2ogr -skipfailures -t_srs $PRJ $DST $SRC -lco GEOMETRY_NAME=the_geom -lco PRECISION=NO

I recall from the PostGIS book there is a better way to deal with this! I really don't want to simply drop the benighted features.

Check your work

The ogrinfo command can peek into your PostGIS database just as it can look into any spatial file it knows how to read. The -so option gives summary output instead of dumping every row to the screen. 

ogrinfo -so PG:"user=postgres db=vietnam" political_boundaries

Loading data from OpenStreetMap

Using excellent instructions from http://bostongis.com/ In particular, the Almost idiot's guide...

First, get the data from CloudMade for California and Oregon 

mkdir /green/GISData/OSM && cd /green/GISData/OSM
wget http://downloads.cloudmade.com/americas/northern_america/united_states/california/california.osm.bz2
wget http://downloads.cloudmade.com/americas/northern_america/united_states/oregon/oregon.osm.bz2

Create a lovely Postgis database 

createdb -U postgres osm -W -T template_postgis

My installed-from-source Postgis did not have hstore.sql so I built it: 

cd ~/src/GIS/postgresql-9.0.6/contrib/hstore
USE_PGXS=1 make && sudo USE_PGXS=1 make install
cd /usr/local/pgsql/share/contrib

Do this each time you create a database a: add hstore support to the database 

psql -U postgres osm < hstore.sql

Build osm2pgsql

No need for any special configuration options, just build and install! 

sudo apt-get install libxml2-dev libbz2-dev
cd ~/src/GIS
svn co http://svn.openstreetmap.org/applications/utils/export/osm2pgsql/
cd osm2pgsql
./autogen.sh
./configure && make && sudo make install

Using osm2pgsql

osm2pgsql oregon.osm.bz2 -d osm -U postgres \
-S /green/bwilson/src/GIS/osm2pgsql/default.style --hstore
osm2pgsql california.osm.bz2 --append -d osm -U postgres \
-S /green/bwilson/src/GIS/osm2pgsql/default.style --hstore

On my little server[ [Bellman]], it took 628 seconds to load the Oregon data and it took 3302 seconds to load California. Conclusion: California is much bigger, in fact there is probably room for me there in Nevada county.

Nice to have some data in my PostGIS server.

Now I need to get it showing up in Geoserver

In the ESRI world

  • I want to be able to move data from ESRI proprietary formats into PostGIS.
  • I want to be able to hand a set of ESRI compatible tools to my GIS Analyst co-workers so they can get the data into my fabled PostGIS data warehouse without my help. (Using ESRI "toolboxes" and ESRI Model Builder for example)

Note although I might be able to use an ArcSDE license (aka ArcGIS Server) to access PostGIS but I regard that as so much extra work it's not worth it. Also it requires an ArcInfo license on the desktop and I would prefer not to.

You only need an ArcGIS license for this to access the ESRI formats. If your data are in shapefiles you don't need this... scroll up.

In fact if your data are in ESRI File Geodatabases that are new (version 10) you can use GDAL 1.9.0 to access them, I can do this with GDAL on Linux, even. But most of my FGDBs are older.

In fact you only need the license for a few things these days.

Iterate a feature class

Here is a simple script (9.3) to iterate over a feature class and read its geometry. The nice thing about using the ESRI code for this is that it does not matter what the data source is, it's just a 'feature class' that can be stored in a shapefile or a personal geodatabase or ArcSDE... etc... 

#!/usr/bin/env python

import arcgisscripting 
gp = arcgisscripting.create(9.3)

# Hard coded data source, for simplicity.
workspace = 'D:/AGIProducts/IncidentView_Data/Data/TEMPORARY_WORKSPACE/WA_King.gdb'
featureclass = 'test_Addresses_points'

gp.workspace = workspace
desc = gp.describe(featureclass) # Get some metadata
shapefieldname = desc.ShapeFieldName
print "ShapeType %s" % desc.ShapeType
print "Indexed =", desc.HasSpatialIndex
print "Shape field", shapefieldname

fields = gp.ListFields(featureclass, '*') # Get a list of the attributes

rows = gp.SearchCursor(featureclass)
row = rows.Next()
i = 0
while row:
    feature = row.GetValue(shapefieldname)
    # If this is a point, we can just grab its shape
    point = feature.GetPart()
    print i, point.x, point.y
    row = rows.Next()
    i += 1

del gp # Release the geoprocessing object
# That's all!

Write the feature to PostGIS

So now I want to put the points into PostGIS... how to do that?

I probably could use the GDAL python bindings. I can probably figure out how to write the geometry directly to PostgreSQL

References

Paulo Corti's notes on Migrating shapefiles to PostGIS from "Thinking in GIS"

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