20.1 Characteristics of Visible Area Map

There could ba some errors for visible area map or quick profile depending on the used digital maps. For example it could be concluded that the mountain A is invisible form the mountain B while the mountain B is visible form the mountain A.

The both of visibility results must be identical independently which point is considered as the view point. This unexpected result is caused by an inaccuracy of the point on the digital map.  For example the top of Mt.Yarigatake has an altitude of 3180 m but the corresponding point of the digital map has far less altitude. This is the reason why the visibility result is concluded negative with the digital map although it is visible actually.

If you use [Tool] - [Visible Area Map] - [Quick Profile] you can reduce such errors above since you can specify correct altitude of the two points.
Also you can create two visible area maps from the both points.

The KashBird has the same effect. The end point of the mountain name line shows the exact altitude of the mountain. You can know the visibility by controlling whether the end point of the line is visible.
You can also setup that the name of the invisible place is not displayed by selecting [Setup] - [Place Name] and checking [Suppress invisible place name].

The altitude of a mesh of the digital map is made of the center altitude or average altitude. This diverse from the real altitude value. This is a reason that the visibility result depends on which point is the view point. Please mind that when you use the result of the visibility.

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