Smoothed Digital Elevation Model (DEM) - 1 arc second resolution - Clipped to Galilee Subregion extent

## **Abstract** \n\nThe dataset was derived by the Bioregional Assessment Programme from the 1 second SRTM Digital Elevation Model (DEM) dataset. The source dataset is identified in the Lineage field in this metadata statement. The processes undertaken to produce this derived dataset are described in the History field in this metadata statement.\n\n\n\nA clipped version of the Australia wide 1 second -S DEM, version 1, which limits the size to the rectangular extent of the Galilee Basin Subregion, enhancing speed and efficiency for visualisation and processing.\n\n\n\nThe metadata for the Geoscience Australia 1 sec SRTM is below:\n\nThe 1 second DSM, DEM, DEM-S and DEM-H are national elevation data products derived from the Shuttle Radar Topography Mission (SRTM) data. The SRTM data is not suitable for routine application due to various artefacts and noise.\n\nThe data has been treated with several processes to produce more usable products:\n\n\\* A cleaned digital surface model (DSM)\n\n\\* regular grid representing ground surface topography as well as other features including vegetation and man-made structures\n\n\\* A bare-earth digital elevation model (DEM)\n\n\\* regular grid representing ground surface topography, and where possible, excluding other features such as vegetation and man-made structures.\n\n\\* A smoothed digital elevation model (DEM-S)\n\n\\* A smoothed DEM based on the bare-earth DEM that has been adaptively smoothed to reduce random noise typically associated with the SRTM data in low relief areas.\n\n\\* A hydrologically enforced digital elevation model (DEM-H)\n\n\\* A hydrologically enforced DEM is based on DEM-S that has had drainage lines imposed and been further smoothed using the ANUDEM interpolation software.\n\n\n\nThe last product, a hydrologically enforced DEM, is most similar to the DEMs commonly in use around Australia, such as the GEODATA 9 Second DEM and the 25 m resolution DEMs produced by State and Territory agencies from digitised topographic maps.\n\nFor any analysis where surface shape is important, one of the smoothed DEMs (DEM-S or DEM-H) should be used. DEM-S is preferred for shape and vertical accuracy and DEM-H for hydrological connectivity. The DSM is suitable if you want to see the vegetation as well as the land surface height. There are few cases where DEM is the best data source, unless access to a less processed product is necessary.\n\nThe 1 second DEM (in its various incarnations) has quite different characteristics to DEMs derived by interpolation from topographic data. Those DEMs are typically quite smooth and are based on fairly accurate but sparse source data, usually contours and spot heights supplemented by drainage lines. The SRTM data is derived from radar measurements that are dense (there is essentially a measurement at almost every grid cell) but noisy.\n\nVersion 1.0 of the DSM was released in early 2009 and version 1.0 of the DEM was released in late 2009. Version 1.0 of the DEM-S was released in July 2010 and version 1.0 of the hydrologically enforced DEM-H was released in October 2011. These products provide substantial improvements in the quality and consistency of the data relative to the original SRTM data, but are not free from artefacts. Improved products will be released over time.\n\nThe 3 second products were derived from the 1 second data and version 1.0 was released in August 2010. Future releases of these products will occur when the 1 second products have been improved. At this stage there is no 3 second DEM-H product, which requires re-interpolation with drainage enforcement at that resolution.\n\n## **Purpose** \n\nTo enhance the speed and efficiency for visualisation and processing of the smoothed 1 second DEM data within the Galilee Basin Subregion\n\n## **Dataset History** \n\nThe original, Australia wide, 1 second smoothed DEM was clipped to rectangular extents of the Galilee subregion using the Spatial Analyst 'Extract By Rectangle' tool in ESRI ArcCatalog v10.0 with the following parameters:\n\nInput raster: source 1 second SRTM\n\nExtent: Galilee Basin subregion polygon\n\nExtraction Area: INSIDE\n\n\n\n'no data' values are created outside the clip extent therefore the extent of the dataset may still reflect the national DEM extent in ArcCatalog. Check the tool details for more info.\n\n\n\nThe lineage of the source 1 second SRTM is below:\n\nThe following datasets were used to derive this version of the 1 second DEM products:\n\n\n\nSource data\n\n1. SRTM 1 second Version 2 data (Slater et al., 2006), supplied by Defence Imagery and Geospatial Organisation (DIGO) as 813 1 x 1 degree tiles. Data were produced by NASA from radar data collected by the Shuttle Radar Topography Mission in February 2000.\n\n2. GEODATA 9 second DEM Version 3 (Geoscience Australia, 2008) used to fill voids.\n\n3. SRTM Water Body Data (SWBD) shapefile accompanying the SRTM data (Slater et al., 2006). This defines the coastline and larger inland waterbodies for the DEM and DSM.\n\n4. Vegetation masks and water masks applied to the DEM to remove vegetation.\n\n\n\nFull metadata, methodologies and lineage descriptions can be found in the PDF userguide within this dataset.\n\n## **Dataset Citation** \n\nBioregional Assessment Programme (2014) Smoothed Digital Elevation Model (DEM) - 1 arc second resolution - Clipped to Galilee Subregion extent. Bioregional Assessment Derived Dataset. Viewed 10 December 2018, http://data.bioregionalassessments.gov.au/dataset/0fe257aa-8845-4183-9d05-5b48edd98f34.\n\n## **Dataset Ancestors** \n\n* **Derived From** [Geoscience Australia, 1 second SRTM Digital Elevation Model (DEM)](https://data.gov.au/data/dataset/9a9284b6-eb45-4a13-97d0-91bf25f1187b)\n\n

## **摘要**

本数据集由生物区域评估计划（Bioregional Assessment Programme）基于1秒航天飞机雷达地形测绘任务（Shuttle Radar Topography Mission, SRTM）数字高程模型（Digital Elevation Model, DEM）数据集衍生而来。源数据集的相关信息详见本元数据声明的**谱系（Lineage）**字段，本衍生数据集的制作流程详见本元数据声明的**历史（History）**字段。

本数据集为澳大利亚全域1秒平滑数字高程模型（DEM-S）V1版本的裁切版本，裁切范围限定为加利利盆地亚区的矩形边界，可提升可视化与处理的速度与效率。

澳大利亚地球科学局（Geoscience Australia）1秒SRTM数据集的元数据如下：

1秒数字表面模型（Digital Surface Model, DSM）、数字高程模型（DEM）、平滑数字高程模型（DEM-S）与水文增强型数字高程模型（DEM-H）均为基于航天飞机雷达地形测绘任务（SRTM）数据衍生的国家级高程数据产品。由于存在多种伪影与噪声，原始SRTM数据不适用于常规应用。

科研人员通过多道处理工序对原始数据进行优化，以生成更具实用性的产品：

- 清洁版数字表面模型（DSM）：代表地表地形及植被、人工构筑物等其他地物的规则格网数据。
- 裸地数字高程模型（DEM）：代表地表地形的规则格网数据，尽可能剔除植被、人工构筑物等非地表地形要素。
- 平滑型数字高程模型（DEM-S）：基于裸地DEM经自适应平滑处理生成的产品，用于削弱低起伏区域SRTM数据常见的随机噪声。
- 水文增强型数字高程模型（DEM-H）：基于DEM-S，通过导入汇流线并使用ANUDEM插值软件进一步平滑处理得到的产品。

上述四类产品中，水文增强型DEM与澳大利亚当前通用的高程模型最为接近，例如GEODATA 9秒数字高程模型，以及各州/领地机构基于数字化地形图生成的25米分辨率DEM。

若分析核心为地表形态，应选用平滑型DEM产品（DEM-S或DEM-H）：DEM-S在地表形态与垂直精度上表现更优，DEM-H则更适用于水文连通性分析。若需同时展示植被与地表高程，可选用DSM产品。原始裸地DEM的适用场景极少，仅当需要未经过多处理的数据源时可选用。

1秒系列DEM产品（含各类衍生版本）与基于地形数据插值生成的DEM存在显著差异：后者通常基于精准但稀疏的源数据（多为等高线、高程点辅以汇流线），整体较为平滑；而SRTM数据源自雷达测量，格网密度极高（几乎每个栅格单元均有测量值）但噪声较强。

DSM V1.0于2009年初发布，DEM V1.0于2009年末发布；DEM-S V1.0于2010年7月发布，水文增强型DEM-H V1.0于2011年10月发布。相较于原始SRTM数据，上述产品在数据质量与一致性上有显著提升，但仍存在少量伪影。后续将持续推出优化版本。

3秒系列产品由1秒数据衍生而来，其V1.0版本于2010年8月发布。后续该系列产品的更新将依托1秒产品的优化进度同步推进。当前暂无3秒分辨率的DEM-H产品，该产品需在对应分辨率下重新进行汇流增强插值处理。

## **数据集用途**

本数据集旨在提升加利利盆地亚区内平滑型1秒DEM数据的可视化与处理效率。

## **数据集制作历史**

本数据集通过ESRI ArcCatalog v10.0的空间分析工具（Spatial Analyst）「按矩形提取（Extract By Rectangle）」，将澳大利亚全域1秒平滑DEM裁切至加利利盆地亚区的矩形边界，具体参数如下：

- 输入栅格：源1秒SRTM数据
- 范围：加利利盆地亚区多边形
- 提取区域：内部区域（INSIDE）

裁切范围外的区域将被赋予「无数据（no data）」值，因此在ArcCatalog中本数据集的范围仍可能显示为全国DEM的范围，详细信息请参阅工具官方说明文档。

源1秒SRTM数据集的谱系信息如下：

本次1秒DEM系列产品的衍生依托以下数据集：

1. SRTM 1秒V2数据（Slater等，2006）：由国防影像与地理空间组织（Defence Imagery and Geospatial Organisation, DIGO）提供，共813幅1×1度分幅瓦片。该数据由美国国家航空航天局（NASA）基于2000年2月航天飞机雷达地形测绘任务获取的雷达数据生成。
2. GEODATA 9秒DEM V3版本（澳大利亚地球科学局，2008）：用于填补原始数据空洞。
3. SRTM水体数据（SRTM Water Body Data, SWBD）shapefile文件（Slater等，2006）：配套SRTM数据发布，用于明确DEM与DSM产品中的海岸线及大型内陆水体范围。
4. 植被掩膜与水体掩膜：用于剔除DEM数据中的植被要素。

完整元数据、制作方法与谱系信息详见本数据集附带的PDF用户指南。

## **数据集引用格式**

生物区域评估计划（2014）：平滑型数字高程模型（DEM）——1弧秒分辨率，裁切至加利利盆地亚区范围。生物区域评估衍生数据集。2018年12月10日查阅，http://data.bioregionalassessments.gov.au/dataset/0fe257aa-8845-4183-9d05-5b48edd98f34。

## **数据集上游数据源**

- **衍生自** [澳大利亚地球科学局，1秒SRTM数字高程模型（DEM）](https://data.gov.au/data/dataset/9a9284b6-eb45-4a13-97d0-91bf25f1187b)