Orthophotos and DSMs derived from RPAS flights over the nature reserve Averbode Bos & Heide in Flanders, Belgium

Study area Averbode Bos & Heide is a nature reserve situated near the locality of Averbode, in the province of Flemish-Brabant, Flanders, Belgium. The area is managed by the nature conservation NGO Natuurpunt and consists of wet and dry heathlands, inland dunes, forests and moorland pools. In the years prior to the drone flights, large stands of mostly coniferous trees were cut to enable ecological restoration of heathlands and moorland pools. The drone flight was triggered by a particular interest to monitor the effects of this restoration. Data collection Data were collected by the Research Institute for Nature and Forest (INBO) with a fixed wing drone Gatewing X100 in 2015 and 2016 (6 flights). RGB data were acquired using an off-the-shelf Ricoh GR Digital IV camera, with the following image bands: 1: red, 2: green, 3: blue, 4: alpha channel. CIR (color-infrared) data were acquired using a NIR-enabled Ricoh GR Digital IV camera, with the following info bands: 1: NIR, 2: red, 3: green, 4: alpha channel. Data processing The raw data were processed to Digital Surface Models and orthophotos by the Flemish Institute for Technological Research (VITO) in 2017. Images with coarse GPS coordinates were imported and processed in Agisoft PhotoScan Pro 1.4.x, a structure-from-motion (SfM) based photogrammetry software program. After extraction and matching of tie points, a bundle adjustment leads to a sparse point cloud and a refined set of camera position and orientation values. From there, a point cloud densification and classification into ground and non-ground points was performed, leading to a rasterized digital surface model (DSM) and digital terrain model (DTM). Finally, a true orthomosaic was projected onto the DTM. Coordinate reference system All geospatial data have the coordinate reference system EPSG:31370 - Belgian Lambert 72. Files Raw flight data: images and logs collected by the drone during flight. These files are zipped per flight, with the date (yyyymmdd) and flight number (x) indicated in the file name (flight_yyyymmdd_ABH_x.zip). Processed data: Digital Surface Models (filename_DSM.tif) and orthophotos (filename_Ortho.tif) stitched together from the raw data. The included flights are indicated in the file name (e.g. 3 flights for 20150928_ABH_1-2_20151001_ABH_1_DSM.tif). Ground control points: not applicable for this dataset. Cloud Optimized GeoTIFF The most efficient way to explore the processed data is by loading the Cloud Optimized GeoTIFFs we created for each processed file. Copy one of the file URLs below and follow e.g. the QGIS tutorial to load this type of file. http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20150928_ABH_1-2_20151001_ABH_1_DSM.tif http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20150928_ABH_1-2_20151001_ABH_1_Ortho.tif RGB http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20151001_ABH_2_DSM.tif http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20151001_ABH_2_Ortho.tif RGB http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20160401_ABH_1_DSM.tif http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20160401_ABH_1_Ortho.tif RGB http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20160401_ABH_2_DSM.tif http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20160401_ABH_2_Ortho.tif CIR See this page for an overview of public INBO RPAS data.

研究区域阿弗尔博德森林与荒原（Averbode Bos & Heide）是坐落于比利时佛兰德斯地区弗拉芒-布拉班特省阿弗尔博德镇附近的自然保护区。该区域由自然保护非政府组织（non-governmental organization, NGO）Natuurpunt管理，涵盖湿地与旱地石楠荒原、内陆沙丘、森林以及荒原水塘。在本次无人机航拍作业开展的数年前，园区内大片以针叶林为主的林分被砍伐，以推进石楠荒原与荒原水塘的生态修复工程。此次航拍任务的实施初衷为监测该生态修复工程的实施效果。

数据采集
数据采集工作由自然与森林研究所（Research Institute for Nature and Forest, INBO）于2015年与2016年完成，累计执行6次飞行任务，搭载平台为固定翼无人机（fixed wing drone）Gatewing X100。RGB影像数据通过商用理光GR Digital IV相机采集，图像波段设置如下：1. 红光波段、2. 绿光波段、3. 蓝光波段、4. Alpha通道。彩色红外（color-infrared, CIR）影像数据则搭载具备近红外（near-infrared, NIR）成像能力的同款理光GR Digital IV相机采集，其波段信息为：1. 近红外波段、2. 红光波段、3. 绿光波段、4. Alpha通道。

数据处理
原始数据于2017年由佛兰德斯技术研究院（Flemish Institute for Technological Research, VITO）处理为数字表面模型（Digital Surface Model, DSM）与正射影像。首先将带有粗略GPS坐标的影像导入Agisoft PhotoScan Pro 1.4.x这款基于运动恢复结构（structure-from-motion, SfM）的摄影测量软件进行处理。通过提取并匹配连接点，执行光束法平差以生成稀疏点云，并优化相机位姿与朝向参数。随后开展点云致密化作业，并将点云分类为地面点与非地面点，最终得到栅格化的数字表面模型（DSM）与数字地形模型（Digital Terrain Model, DTM）。最后将真实正射镶嵌图映射至数字地形模型（DTM）之上。

坐标参考系统
所有地理空间数据均采用EPSG:31370——比利时兰伯特72（Belgian Lambert 72）坐标参考系统。

文件
原始飞行数据：包含无人机飞行期间采集的影像与日志文件。该类数据按单次飞行打包为ZIP压缩包，文件名包含拍摄日期（格式为yyyymmdd）与飞行编号（x），命名格式为flight_yyyymmdd_ABH_x.zip。处理后数据：包含数字表面模型（文件命名格式为filename_DSM.tif）与正射影像（文件命名格式为filename_Ortho.tif），二者均由原始影像数据拼接生成。文件名中会标注所涵盖的飞行任务信息，例如20150928_ABH_1-2_20151001_ABH_1_DSM.tif即包含2015年9月28日ABH飞行1-2以及2015年10月1日ABH飞行1的相关数据。地面控制点：本数据集未提供地面控制点。

云优化GeoTIFF
浏览处理后数据的最高效方式为加载我们为每份处理文件生成的云优化GeoTIFF（Cloud Optimized GeoTIFF）。可复制下方任一文件URL，并参考QGIS教程加载此类文件：
http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20150928_ABH_1-2_20151001_ABH_1_DSM.tif
http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20150928_ABH_1-2_20151001_ABH_1_Ortho.tif RGB
http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20151001_ABH_2_DSM.tif
http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20151001_ABH_2_Ortho.tif RGB
http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20160401_ABH_1_DSM.tif
http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20160401_ABH_1_Ortho.tif RGB
http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20160401_ABH_2_DSM.tif
http://s3-eu-west-1.amazonaws.com/lw-remote-sensing/cogeo/20160401_ABH_2_Ortho.tif CIR
可访问此页面查看INBO公开的遥控无人机系统（Remotely Piloted Aircraft System, RPAS）数据概览。