Loading data into PostGIS

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

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

Loading data

First method: Loading shapefiles with shp2pgsql

Use the shp2pgsql command to create and load the table and then manually define the projection. You have to know the EPSG code for the projection. Google... 2992 is the Oregon state 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 $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

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

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"