@unpublished{TUW-280992, author = {Retscher, G{\"u}nther}, title = {Positioning with Signals-of-Opportunity in Challenging Transitional and Indoor Environments}, year = {2019}, note = {invited; talk: Guest Lecture at the Faculty of Geomatics of Sabaragamuwa University of Sri Lanka, Belihuloya, Sri Lanka; 2019-07-02} }