50' Contour Lines - Gila County

This dataset represents 50 foot contour intervals for Gila County, Arizona. The data were created by processing hillshade TIF files derived from the U.S. Geological Survey National Elevation Dataset. The processing produced ESRI formatted coverages for each county or part of a county. The U.S. Geological Survey has developed a National Elevation Dataset (NED). The NED is a seamless mosaic of best-available elevation data. The 7.5-minute elevation data for the conterminous United States are the primary initial source data. In addition to the availability of complete 7.5-minute data, efficient processing methods were developed to filter production artifacts in the existing data, convert to the NAD83 datum, edge-match, and fill slivers of missing data at quadrangle seams. One of the effects of the NED processing steps is a much-improved base of elevation data for calculating slope and hydrologic derivatives. The specifications for the NED 1 arc second and 1/3 arc second data are - Geographic coordinate system, Horizontal datum of NAD83, except for AK which is NAD27, Vertical datum of NAVD88, except for AK which is NAVD29, Z units of meters.本数据集涵盖美国亚利桑那州希拉县（Gila County）的50英尺等高距数据。数据通过处理源自美国地质调查局（U.S. Geological Survey）国家高程数据集（National Elevation Dataset, NED）的晕渲地貌TIF文件生成。该处理流程为各县级行政区或其下辖区域生成了ESRI格式的要素覆盖数据集。 美国地质调查局已构建国家高程数据集（NED），该数据集为当前可获取的最优高程数据的无缝镶嵌成果。美国本土48州的7.5弧分高程数据为其核心初始源数据。除完整提供7.5弧分高程数据外，研发团队还开发了高效处理流程，用于滤除现有数据中的生产伪影、将数据转换至NAD83大地基准、开展边缘匹配，并填补图幅接缝处的缺失数据碎片。 NED的处理流程带来的一项显著优势，是为坡度与水文衍生参数的计算提供了精度大幅提升的高程基础数据集。 NED 1弧秒与1/3弧秒数据的规范如下：采用地理坐标系，水平基准为NAD83（阿拉斯加州，简称AK，除外，其水平基准为NAD27）；垂直基准为NAVD88（阿拉斯加州，简称AK，除外，其垂直基准为NAVD29）；Z轴单位为米。