Description: This data set represents a 2-meter resolution LiDAR-derived normalized Digital Surface Model (nDSM) or Canopy Height Model (CHM) for New Hampshire. It was derived from a statewide LAS Dataset which comprised 8 separate LiDAR collections that covered the state as of January, 2020. The LAS Dataset was used as input to the ArcGIS "LAS Dataset to Raster" geoprocessing tool which converted the LAS first return values to raster values in the output data set. Subsequent processing subtracted the corresponding "bare earth" surface values to produce estimated feature height. It is recognized that this is a simplistic approach to the challenge of estimating LiDAR-based first return heights. Users should recognize this and keep it in mind when using the data.
In some areas, users may notice unusual linear edges which appear unlikely or anomalous. The LiDAR vendor explained that these anomalies may be the result of changes in the degrees of tree canopy closure that occurred between the times adjacent flight lines were completed. Although leaf-off conditions were specified for data collection, strict adherence to the project specifications was not possible in all locations and exceptions occurred in order to complete data acquisition in a timely manner. As a result, abrupt discontinuities may be noticeable where data were collected on different dates. Eamples of these anomalies can be found in the areas of Cave Mountain in Bartlett and to the west of Woodstock.
Description: This data set represents a 2-meter resolution LiDAR first return surface or Digital Surface Model (DSM) for New Hampshire. It was derived from a statewide LAS Dataset which comprised 8 separate LiDAR collections that covered the state as of January, 2020. The LAS Dataset was used as input to the ArcGIS "LAS Dataset to Raster" geoprocessing tool which converted the LAS first return values to raster values in the output data set.
In some areas, users may notice unusual linear edges which appear unlikely or anomalous. The LiDAR vendor explained that these anomalies may be the result of changes in the degrees of tree canopy closure that occurred between the times adjacent flight lines were completed. Although leaf-off conditions were specified for data collection, strict adherence to the project specifications was not possible in all locations and exceptions occurred in order to complete data acquisition in a timely manner. As a result, abrupt discontinuities may be noticeable where data were collected on different dates. Eamples of these anomalies can be found in the areas of Cave Mountain in Bartlett and to the west of Woodstock.