Underground Mined Areas of Oilshale
Data are based on the study carried out by the Tallinn Technical University in 2014-2015 "Põlevkivi altkaevandatud alade planšettide digitaliseerimine ja stabiilsushinnangu andmine (In Estonian)" ( 616.7 KB, 18.12.2015 ) .
The study was focused on digitizing the old underground oilshale mining areas and georeferencing the coordinates with the national L-EST97 system. The polygons were classified according to stability estimation.
Later (2018) another project "Põlevkivi altkaevandatud alade varingute uuring (In Estonian)" was carried out by the Tallinn Technical University.
Both projects were financed by the Environmental Investment Centre.
The Land Board made a topological revision of the data. Hole layer was supplemented with objects from the later (2018) survey.