The Database Previewer is a multi-purpose interface to the noise model. Its main purpose is to let you download the model for a particular scenario and a particular area. When you select the scenario of interest in the upper window of the previewer, NoiseMap highlights only the tiles where one or more geographical features are different from the features of its parent scenario.
However, if you want to see the complete model for the scenario, you also need to include the tiles from the parent scenario which were not altered in the child scenario, so you check the 'Include parent scenario' box. This may cause a large number of additional tiles to be downloaded, but you can limit this by using the 'named area' feature.
Note that in the previewer, selecting a named area does not include the unaltered tiles from the parent unless you tick the 'include parent scenario' option.
Also, remember that only the tiles visible and highlighted in the display will be downloaded. This also helps to prevent very large areas to be loaded by mistake.
However, when editing or printing out a model, be careful not to inadvertently exclude tiles: in these cases it is normally necessary to ensure that the 'include parent tiles' box has been ticked.
