Sprawling Mayan network discovered under Guatemala jungle

Re:Sprawling Mayan network discovered under Guatemala jungle by ziotom78 on Friday February 02, 2018 @03:38PM (#16294015)

The is one thing I don't understand. The article reports the use of lasers to map the ground, yet they mention the presence of foliage in situ. Assuming that they use optical or infrared lasers, foliage should be completely opaque at these wavelengths. How did they manage to map the asperities and characteristics of the ground?

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Re:Sprawling Mayan network discovered under Guatemala jungle by Dangeranger on Friday February 02, 2018 @04:27PM (#16294330)

LiDAR wavelengths are returned at various depths from within the forest canopy. In order to get a return on the ground you simply filter the returns down to the last value.

Sometimes however you want to keep the other returns and so you filter the values down to say 10% of all returns from a given depth, with a constraint between the depths of say 10cm so that you can see the density of the layers.

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Re:Sprawling Mayan network discovered under Guatemala jungle by Pica_soO on Friday February 02, 2018 @03:47PM (#16294075)

A filter that takes the most deepest z-value you get, considering all else in a square meter as noise- or foliage?

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