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NYPL Map Warper

Deprecation notice

As of April 2021, Mapwarper will no longer be updated by NYPL, and will soon be archived. This means all embedded views utilizing Mapwarper will no longer work once the site is archived. However, all contributions and data will be retained by the Library for future use and research.

Thank you for your interest and use of the tool.

This software has been developed by Topomancy LLC with the support and collaboration of the New York Public Library.

You can see this code in action at

Consult the wiki for for more documentation including a report detailing the changes in this version compared with the previous version.

The NYPL Map Warper is an open source map geo-rectification, warping and georeferencing application. It enables a user to browse and explore the NYPL's historical map collection, and by placing control points on a reference map and the image, to warp it, to stretch it to fit.

Map Warper screenshot of main interface

The application can be seen in use at

The application is a web based crowdsourced geospatial project that enables people and organisations to collaboratively publish images of maps online and digitize and extract vector information from them.

Users rectify, warp or stretch images of historical maps with a reference basemap, assigning locations on image and map that line up with each other. Often these historical maps were in big paper books, and so for the first time they can be stitched together and shown as a whole, in digital format.

Users can crop around the maps, and join them together into layers.

By georeferencing the images, they can be warped or georectified to match the locations in space, and used in GIS software and other services. One such use of these warped maps is an application that that helps people digitize, that is, trace over the maps to extract information from them. For example, buildings in 18th Century Manhattan, details changing land use, building type etc. This application is called the Digitizer.

The application runs as a Ruby on Rails application using a number of open source geospatial libraries and technologies, including PostGIS, Mapserver, Geoserver, and GDAL tools.

The resulting maps can be exported as a PNG, GeoTIFF, WMS, Tiles, and KML for use in many different applications.


  • Find and search maps by geography
  • Adding control points to maps side by side
  • Crop maps
  • User commenting on maps
  • Align maps from similar
  • Login via Github / Twitter / etc
  • OR signup with email and password
  • Export as GeoTiff, PNG, WMS, Tile, KML etc
  • Preview in Google Earth and Google Maps
  • Map Favourites
  • Social media sharing
  • Bibliographic metatadata creation and export support
  • Multiple georectfication options
  • Control point from files import
  • API
  • Admin tools include
    • User statistics
    • Activity monitoring
    • User administration, disabling
    • Roles management (editor, developer, admin etc)
    • Batch Imports
    • User Flags
    • User Statistics
    • Revisions and Rollbacks

Note on code and branches

Unmaintained branches exist for older systems and setups

  • Rails 2.3 and Ruby 1.8.4 - See the rails2 branch

Ruby & Rails

  • Rails 4.2
  • Ruby 1.9+


  • Postgresql 9.1 (or 9.1, 8.4)
  • Postgis 2 (may work with 1.5)

Installation Dependencies

Check out the Vagrant section lower down in the readme if you want to get started quickly.

on Ubuntu 14.04 LTS

apt-get install -y ruby ruby-dev postgresql-9.3-postgis-2.1 postgresql-server-dev-all postgresql-contrib build-essential git-core libxml2-dev libxslt-dev imagemagick libmapserver1 gdal-bin libgdal-dev ruby-mapscript nodejs

Due to a bug with the gdal gem, you may need to disable a few flags from your ruby rbconfig.rb see zhm/gdal-ruby#4 for more information

Then install the gem files using bundler

bundle install


Create and configure the following files

  • config/secrets.yml
  • config/database.yml
  • config/application.yml

In addition have a look in config/initializers/application_config.rb for some other paths and variables, and config/initializers/devise.rb for devise and omniauth and also config/environments/development.rb if you rather not use the /warper relative path.

Database creation

Create a postgis database

sudo -u postgres createdb mapwarper_development
psql mapwarper_development -c "create extension postgis;"
RAILS_ENV=development bundle exec rake db:migrate

Database initialization

Creating a new user

user =
user.login = "super" = ""
user.password = "your_password"
user.password_confirmation = "your_password"
user.confirmed_at =

role = Role.find_by_name('super user')

permission  =
permission.role = role
permission.user = user

role = Role.find_by_name('administrator')
permission =
permission.role = role
permission.user = user


Via Vagrant, there is a Vagrantfile you can use which uses the /lib/vagrant/ provision script. Note: the default Vagrantfile is configured to take 8GB RAM. To use this file type:

vagrant up

to get and install the virtual machine - this will also install the libraries and depencies and ruby gems for mapwarper into the virtual machine. See /lib/vagrant/ for more details about this process.

After that runs, type vagrant ssh to login and then you can:

cd /srv/mapwarper
rails c

Create a user in the console, as shown above and then exit. Then start the server in a relative url root use thin:

RAILS_ENV=development bundle exec thin --prefix=/warper start

and then browse to http://localhost:3000/warper/

In non-Vagrant circumstances you may want to run it just using rails s.

Import a test map

This codebase only supports maps from NYPL via the Digital Collections API (use that link to get an account and token). Fortunately, many of our maps are Public Domain so you can test the warper locally (non PD maps are not downloadable in high-res from the API). The warper imports maps (subject to throttling limits) based on the UUID visible in the item page (98b7f36a-3d7a-6c65-e040-e00a18064b00 in this case):

  1. add the generated API token to /config/nypl_repo.yml
  2. start the server and log in with a super user
  3. go to Admin / Imports
  4. Click Add New Import
  5. Select Import Type: Map and type in the UUID: a66456f6-3860-95d5-e040-e00a18065ecc and click Create
  6. Click Start Import

This will take a few minutes to pull the map. You now have a map you can work with and test functionality!

Deployment instructions

The system can use capistrano for deployment.

Making Code Changes and Deployment

There are two main changes to the system. Changes to checked in code, and changes to configuration files. Some configuration files (/config/*) are not stored in the repository. To change these you need to ssh into the server and change the file. Some .example files are provided for reference.

Changes to checked in code.

Develop, patch the code locally and get it running. Probably the easiest way to start developing is via Vagrant, see above for more details. Once you have Vagrant running, these are some useful commands to make sure updates are reflected:

If assets had been changed (images, JS, CSS etc.) or if you just want to be safe:

RAILS_ENV=production rake assets:clobber

RAILS_ENV=production rake assets:precompile

If necessary to run rails console commands:

RAILS_ENV=production rails console

To restart the server:

touch tmp/restart.txt

To restart the Apache server (not needed in almost all cases):

sudo service apache2 restart

Changes to config file:
  1. ssh into the server
  2. Find the desired config file
  3. Edit the file
  4. Restart the warper: touch tmp/restart.txt


See for API details