Accurate separation of global tilted irradiance (GTI) becomes importantwhen the measured irradiance is used for quality control or PV simulationpurposes, for which the latter often requires global horizontalirradiance (GHI), or diffuse and beam irradiance fractions. This studypresents an evaluation of irradiance reverse transposition and separationmodels for the application with GTI in high latitudes. The evaluationis made based on measured and quality controlled six-second irradiancefrom latitude 59.53°N, containing GTI at 30°, 40°, and 90° tiltangles, as well as GHI and diffuse horizontal irradiance (DHI). Basedon a literature review, two specialized GTI reverse transposition andseparation models - GTI-DIRINT and Perez-Driesse - and four GHIseparation models were chosen for evaluation. The latter were testedin an optimization loop developed for this study that utilizes existingGHI separation models combined with transposition models for reversetransposition and separation of GTI. Specifically, the separation modelsErbs, Skartveit1, Engerer2, and Yang4 were tested with Hay &Davies and Perez1990 transposition.The models were investigated using both statistical evaluation metricsand Diebold-Mariano test to compare measured and predicted GHI and DHI. An evaluation with measured data showed that for GTI reversetransposition and separation at high latitudes, the use of the proposedoptimization model with Engerer2 in combination with Hay & Daviestransposition, or the Perez-Driesse model is recommended. This isbased on overall good ranking and low bias of GHI prediction with -2.0W/m2 and -2.3 W/m2, respectively.