Open workflow for digitizing notified maps from the Gazette

[Arun Ganesh]

Some of you may be aware that the Gazettes are an authoritative source of open data and maps published by the Government, but they are not usable when published in the original PDF format.

Example of some of the maps available in the gazettes:

- Notifications of protected area boundaries and eco sensitive zones by MoEFCC: Link

- Changes to irrigation command areas (Goa): Link

The wildlife protected area and ESZ boundaries are especially valuable since they restrict various commercial and industrial activity in the vicinity of ecologically sensitive areas. The notified maps however are usually in low resolution without georeferencing making it close to impossible to use it to investigate if a map location falls in a protected area.

Georeferencing workflow

To overcome this, have been trying out seamless a workflow to georeference and digitize the maps on OpenStreetMap that will open up the data for wider uses. The workflow is described here: https://github.com/publicmap/amche-atlas/issues/230#issuecomment-4866156628

It makes use of the IIIF manifest.json available on any document on internet archive to seamlessly load a Gazette map in the AllMaps.org georeferencer using a SOI toposheet as a basemap. The georeferenced image can then be loaded as a TMS layer in OSM or QGIS for digitizing. The process involves no download/image processing/upload steps at all and is completely on the cloud with free tools.

Following this method, was able to digitize the core and eco sensitive zone boundaries of Tansa and Tungareshwar Wildlife sanctuaries in significant detail in under an hour. Hope it is useful for those working on environmental/legal matters.