Elevation from Lidar (Image Service)

This is a seamless bare earth digital elevation model (DEM) created from lidar terrain elevation data for the Commonwealth of Massachusetts. It represents the elevation of the surface with vegetation and structures removed. The spatial resolution of the map is 1 meter. The elevation of each 1-meter square cell was linearly interpolated from classified lidar-derived point data. This version of the DEM stores the elevation values as integers. The native VALUE field represents the elevation above/below sea level in meters. MassGIS added a FEET field to the VAT (value attribute table) to store the elevation in feet as calculated by multiplying VALUE x 3.28084. Dates of lidar data used in this DEM range from 2010-2015. The overlapping lidar projects were adjusted to the same projection and datum and then mosaicked, with the most recent data replacing any older data. Several very small gaps between the project areas were patched with older lidar data where necessary or with models from recent aerial photo acquisitions. See https://www.mass.gov/doc/lidar-project-areas-original/download for an index map. This DEM is referenced to the WGS_1984_Web_Mercator_Auxiliary_Sphere spatial reference. See the MassGIS datalayer page to download the data as a file geodatabase raster dataset. View this service in the Massachusetts Elevation Finder.本数据集为马萨诸塞州基于激光雷达地形高程数据制作的无缝裸地数字高程模型（DEM）。该模型移除了地表植被与人工构筑物，呈现移除后的地表真实高程。本数据的空间分辨率为1米，每个1米见方栅格单元的高程值均由分类后的激光雷达点云数据通过线性插值得到。本版本DEM以整数格式存储高程数值，原生VALUE字段代表以米为单位的海拔（含低于海平面的情况）。马萨诸塞州地理信息系统（MassGIS）在值属性表（Value Attribute Table，VAT）中新增FEET字段，通过将VALUE字段值乘以3.28084，以英尺为单位存储高程数据。本DEM所用激光雷达数据的采集时间范围为2010年至2015年。重叠覆盖的激光雷达项目已统一投影基准与大地基准面并进行镶嵌拼接，以最新数据覆盖旧有数据。项目区域间存在的少量细小空隙，必要时将通过旧激光雷达数据或近期航空摄影获取的地形模型进行补全。可访问https://www.mass.gov/doc/lidar-project-areas-original/download 下载项目区域索引地图。本DEM采用WGS_1984 Web墨卡托辅助球体空间参考坐标系。用户可通过MassGIS数据图层页面下载该数据的文件地理数据库栅格数据集版本，也可在马萨诸塞州高程查找器中查看该服务。