The transmission network map is obtained from the OpenStreetMap (OSM) database version 06.Feb.2017. The level of completeness varies across different areas due to poor satellite/aerial imagery and/or resolution in some areas, and due to a lack of OSM editors to help improve the data. If you are interested in improving this dataset, you can do so by further digitizing the available imagery with the in-browser OSM ID Editor - http://ideditor.com/ using the guidance available on the OSM Wiki - https://wiki.openstreetmap.org/wiki/Main_Page
OSM is a collaborative project to create a free editable map of the world. Map data is collected from scratch by volunteers using GPS, local knowledge and other free sources of information and then entered in the OSM database. The resulting map can be viewed and downloaded from the OSM server: http://www.OpenStreetMap.org. Every user is encouraged to contribute back to the OSM database.
OpenStreetMap® is open data, licensed under the Open Data Commons Open Database License (ODbL) by the OpenStreetMap Foundation (OSMF).