I received a comment about NDSM (Normialized Digital Surface Model). I looked it up and it is a representation of elevation objects on a flat surface. It is genrated by using the difference between the DSM and DTM. Anyone care to elaborate on this?

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2 Responses to DEM/DSM/DTM…NDSM?

  1. Bob Williams says:

    The best example of normalized LiDAR data can occur and is common on parking lots. Small “puddles” and “peaks” that don’t exist in reality, typically .05 to .2′ elevation differences, and most often introduced by the intensity of the return. The noise points are amplified if contours are generated. These points can be normalized through breaklines around the parking areas, filtering and smoothing of the LiDAR prior to publishing the final DTM. Hence the strong argument that breaklines do matter, even beyond hydro-flattening specifications.

    • bloglidar says:

      I do agree with most of this but the “noise in parking lots or paved surfaces are a function of the operation of the LiDAR sensor and the “noise” is not indicative of a given manufacture rather individual lidar sensors and the settings used during the collection of a given sensor. I have seen excellent results with all of the manufacturers including Optech, Leica, and Riegl. The faster repetation rates at higher altitudes pushing the operational envelop usually cause “noise” on paved surfaces but there are other variables that cause a magnification of “noise” on paved surfaces. If the sensor is operated properly the result doesn’t require the need for breaklines.

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