NoiseMap Forums
NoiseMap Software => Support => Topic started by: roger on May 11, 2015, 11:38:13 AM
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The receiver parameter 'Height above local' (Enterprise) or 'Height above ground' (NoiseMap five) is normally only used when generating the receiver height from the ground model. Receiver heights are only generated when you click 'Get height' during the receiver generation process. The receiver height is then stored as Height (Height above datum in Enterprise) and this value is used in all subsequent calculations. The height above ground, which is required in order to calculate the average height of propagation, is then obtained at calculation time by finding the height of the ground at the receiver point.
Obviously, if you have not entered any ground contours, then NoiseMap can't use them to get the height above ground. In this situation, it uses the parameter 'height above local ground' to calculate the average height of propagation, by assuming that the ground follows a steady slope between the edge of the road and the position of the receiver.
Note that if you change the ground model after generating the receivers, this could cause a problem. A receiver could end up at the wrong height above the ground. So you may need to regenerate all the receiver heights. In NoiseMap five, this is straightforward. Select all the receivers (the easiest way is to switch off all objects except the receivers and then drag the selection box around them.) Open the Object properties window. This will show the Multiple Receiver Properties window and you will see that height above ground is one of the parameters. Click on 'Calculate new height' and choose the method from the drop-down list. This will recalculate all the receiver heights, using the height above ground already assigned to each receiver. Then save the new values. (Be sure to do this in the Root Scenario of the receivers so that the new heights propagate through to child scenarios.)