An aircraft head-up display system, comprising: a processing unit; a database; and a head-up display coupled to the processing unit; wherein the processing unit is configured to: generate display control signals for projecting non-geo-referenced symbology (202, 206,210,212,216); generate display control signals for projecting geo-referenced symbology (220, 222, 224, 226, 228); characterised by being further configured to receive terrain data from the database, including terrain features disposed in front of the geo-referenced symbology (220, 222, 224, 226, 228); generate display control signals representing, in a black color, said terrain features based on the terrain data; and send the display control signals for non-geo-referenced symbology, the display control signals for geo-referenced symbology, and the display control signals for said terrain features to the head-up display such that the black color of said terrain features in the display control signals from the processing unit is transparent when viewed on a combiner of the head-up display while masking portions of the geo-referenced symbology obscured by said terrain features in front. a processing unit; a database; and a head-up display coupled to the processing unit; wherein the processing unit is configured to: generate display control signals for projecting non-geo-referenced symbology (202, 206,210,212,216); generate display control signals for projecting geo-referenced symbology (220, 222, 224, 226, 228); characterised by being further configured to receive terrain data from the database, including terrain features disposed in front of the geo-referenced symbology (220, 222, 224, 226, 228); generate display control signals representing, in a black color, said terrain features based on the terrain data; and send the display control signals for non-geo-referenced symbology, the display control signals for geo-referenced symbology, and the display control signals for said terrain features to the head-up display such that the black color of said terrain features in the display control signals from the processing unit is transparent when viewed on a combiner of the head-up display while masking portions of the geo-referenced symbology obscured by said terrain features in front. generate display control signals for projecting non-geo-referenced symbology (202, 206,210,212,216); generate display control signals for projecting geo-referenced symbology (220, 222, 224, 226, 228); characterised by being further configured to receive terrain data from the database, including terrain features disposed in front of the geo-referenced symbology (220, 222, 224, 226, 228); generate display control signals representing, in a black color, said terrain features based on the terrain data; and send the display control signals for non-geo-referenced symbology, the display control signals for geo-referenced symbology, and the display control signals for said terrain features to the head-up display such that the black color of said terrain features in the display control signals from the processing unit is transparent when viewed on a combiner of the head-up display while masking portions of the geo-referenced symbology obscured by said terrain features in front.