b'Magnetics in the mountainsFeatureFigure 5.North-south profile through the data sets in Figure 4: Left hand axis, observed magnetic data (red), forward modelled data (gold), upward continued pseudomag topography (green). Right hand axis; SRTM30 (blue).before flying commenced, and took eight months to run onshows a comparison between the two data sets along a a dual hexacore with 192 GB of RAM. It finished just as theNS trending profile through the data. The pseudomag final interpretation was being written up. Both processestransformed topography has been multiplied by 0.032 so that used a 30 m x 30 m horizontal pixel/voxel size. The forwardit can share an axis with the forward modelled response and modelling used 15 m thick voxels down to the lowest pointallow the SRTM topography profile to be included on the right in the topography, then increased the voxel thickness byhand axis. The differences between the two magnetic data a factor of 1.1 with depth, to extend the mesh to 3.5 kmsets are of the order of a few nanoTeslas, which is well within below the lowest point in the topography. As I did not havethe experimental error.accurate bathymetry, I allowed the model to assume that the sea surface was the land surface. Both assume a constantBecause of the edge and panelling effects suffered by the drape of 60 m above ground, which tallied with the flyingforward model it could easily be argued that the transformed height after tree height was added to the measured radartopography was a better data set to work withat least from a altimeter. For the rotated topography this was achieved bysubjective interpretation perspective. Because of the time taken upward continuing the data by 60 m. to run the forward model in this case, it was the only data set to work with.Figure 6 shows a comparison between the MAGFOR3D generated forward model of the topography for the surveyThe re-scaling factor of 0.032 for the pseudomag transformed block and a pseudomag transform of the 30 m SRTM. Thedata was derived from a scatter plot of the two data setssee panelling and edge effects in the south are evident in theFigure 8.modelled data but otherwise the two data sets correlate very well. unfortunately I dont have permission to show you the realFor the majority of mainland Australia, topography, at the scale magnetic data here, but I can say that having the pseudomagwhere it becomes an issue for aeromagnetic interpretation, transformed topography assisted greatly in the interpretation ofis largely absent. This is not the case for Tasmania, which has the magnetic data. managed to retain some hills, particularly on the west coast. Figure 9 shows a comparison of elevation, from the SRTM 30, In support of the correlation between the forward modelledwith observed magnetic data for an area just to the east of data and the pseudomag transformed topography, Figure7Waratah. The elevation range here is 900 m, while the range 37 PREVIEW JuNE 2020'