The generation of accurate Line of Sight (LOS) visibility information consumes significant resources in large scale synthetic environments such as many-on-many serious games and battlefield simulators. Due to the importance of optimum utilisation of computing resources, a number of LOS algorithms are reported in the literature to either efficiently compute LOS information or reduce the impact of LOS queries on the run-time performance of synthetic environments. From the literature it is known that a k-dimensional tree (kd-tree) based raytracing approach, to calculating LOS information, is efficient. A new implicit min/max kd-tree algorithm is discussed for evaluating LOS queries on large scale spherical terrain. In particular the value of low resolution boundary information, in quickly evaluating the LOS query, is emphasised. The min/max algorithm is empirically compared to other LOS approaches that have either implicitly or explicitly used kd-trees to optimise LOS query evaluation. T...