Frequently Asked Questions

Your use of rə is subject to Google's Terms of Service and Privacy Policy. Please read both of those documents to learn more. Some of the most frequently asked questions are answered on this page.

rə use of information received from Google APIs will adhere to Google API Services User Data Policy, including the Limited Use requirements.

rə relies on crowdsourcing to create a historical map of the world. We have two major web applications to support this process: Warper and Editor. Warper lets you upload scans of historical maps and georectify them by adding control points to the historical map and corresponding points on a contemporary map. The scanned map is then warped so that it aligns well with the underlying contemporary map. Warped maps can then be viewed in the Editor web application, where users can trace map features such as building footprints, roads, etc., add information (metadata) about each feature such as the number of floors of a building or the name of a road, and uplaod and annotate images of buildings.

Is the site broken?

If you experience glitches, please log an issue in our Github project or contact us at

Contributions and Maps

Maps: When you upload a map to Warper you agree that you are lawfully entitled and have full authority to license this website to use the uploaded map and make it publicly available. You can delete your maps at any time. Deleting a map also deletes all its associated Contributions in Warper. Any Contribution made in Editor using the deleted map as a background stays indefinitely in our database and is not meant to be deleted. If you believe someone has uploaded a Map that is not theirs, or that you own the copyright to, you can contact us at with your concerns.

Contributions: You can contribute to this project by adding/deleting/modifying control points of Maps in Warper. A control point associates a point on a Map with its location on a contemporary map. A collection of control points are then used to rectify the Map. You can also quickly and roughly place Maps that are not rectified yet. This will help others to add control points. Finally, you can help us by cropping the Maps. All of these data points are considered your “Contributions” in Warper. You can also contribute by tracing rectified maps from Warper with Editor. To do this you load the rectified map as the background map of Editor and trace the map features (building footprints, roads, etc.) and add metadata (street address, number of floors, start date, etc.). The traced map features and their metadata might be extracted from the historical map or your personal knowledge. You can also delete/modify the map features and metadata created by others. All of these data points are considered your “Contributions” in Editor. When we say Contributions in this document we mean your Contributions in both Warper and Editor, unless otherwise specified.

Do I have to make my contributions available for others to use?

Yes. All of your Contributions will be made available to others pursuant to an open source license. By agreeing to open source your Contributions, you hereby grant to Google and to recipients of copyrightable material distributed by Google a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute your images. You represent that you are legally entitled to grant this license.
If moral rights apply to your Contributions, to the maximum extent permitted by law, you waive and agree not to assert such moral rights against Google or Google’s successors in interest, or any of Google’s licensees, either direct or indirect.

Will I get paid for my contributions?

No. rə is a community effort–we rely on the goodwill of community members to help us revive the past and together build a mapping service with a time dimension, such that everybody in the world can benefit.

How can I delete the images/maps that I have uploaded?

In Warper, go to the Edit tab of the Map you want to delete and click on the “Delete this map” link. This will delete the map from our servers, however, note that maps are publicly available; deleting a map from our servers will not ensure that every copy of it is deleted, since others may have copied or reused the image prior to deletion. If you delete your account, all the maps that you have uploaded are also deleted. This is not reversible.

How can I delete my Contributions?

Your Contributions are open sourced. You can manually delete your Contributions, but they will still be recorded in the activity tab of the application. For example, if you put control points on a map and later delete them, the activity tab of the map will show the creation and deletion of the control points and will let other users revert your changes. You cannot wipe out your Contributions to the open sourced data of rə. If you delete your account, your Contributions will be de-identified (that is, they’re no longer associated with your account) but they will not be deleted. It’s important to understand that Google is not able to find, delete, or de-identify any copies of your Contributions that other users may have created while the Contributions were open-sourced, nor is Google able to revoke an open-source license to those Contributions once they’ve been distributed.

How do you use my Contributions?

The Contributions that you make are stored on our servers and are open sourced such that they are publicly accessible. We may use this information to process other data (e.g., warping a map based on control points) or serve them directly. We may validate your Contributions by automatic or manual processes. Contributions may be used to train computer algorithms and improve Google’s products and services. Note that since your Contributions are open sourced, we have no control on how they will be used by others.

Images of buildings that you upload and annotate will be used for creating of 3D reconstructions of buildings. If uploaded image is marked as 'Public' at time of upload, or at a later time, it may be displayed for other visitors of rə to see. Upladed image can be deleted by uploader, its visibility can be changed; semantic information about the building extracted from the image (if any), and annotations cannot be deleted.


You must login to your Google account prior to submitting any Contributions or Maps. This is to aid in the system identifying you correctly. The email address for your account will never be published anywhere or shared with third party organisations. Only administrators have direct access to email address data.

Account Removal

You can delete your rə account at any time by emailing us at Deleting your rə account will not delete your Google accout -- it just deletes your Google account's association with rə. Deleting your account will also delete your uploaded Maps and user profile, but it will not delete your Contributions. Such contributions will be de-identified.


Cookies are very small text files that are stored on your computer when you visit some websites. We use cookies to help keep a track of whether you are logged in and to aid site navigation state. You can disable any cookies already stored on your computer, but these may stop our website from functioning properly. This website will remember that you are logged in and that your session is secure. You need to be logged in to upload maps. You can also disable third party cookies to disable Google Analytics.

Google Analytics

This system may use Google Analytics so we can get statistics about how users use the website so we can improve it. IP addresses are anonymized.

Other uses of your data

IP Addresses

The IP address of each request is stored in the application and web server logs for the purpose of maintentance, security and abuse prevention. These logs are deleted after 30 days.

Map metadata

When you upload a map with a title and description, this website sends the image to Google's Cloud Vision API to extract text (OCR) and the OCR text from that with the title and description to Google Maps API for Geocoding . This is to attempt to give a best guess place for your map. For example if you upload an image with the title "Paris, France" it may zoom the map to that location for you

Exported Data License

All data exported from rə is made available under the Open Database License: Any rights in individual contents of the data are licensed under the Database Contents License: