Ngozumpa Glacier Gokyo ice cliffs photographic surface model

Data files of a photographic surface model of three ice cliffs exposed on the surface of the Ngozumpa Glacier ( 27°57′N, 85°42′E), Nepal, near the village of Gokyo. Details of how the data were produced: 1160 full resolution JPEG images were used to make the difgital surface model (DSM) Photos were taken using Nikon D5000 with 100mm Tamron macro lens on 4th April 2016 7 ground control points (GCPs) within the captured scene were used to scale and georeference the DSM GCPs were measured using a Trimble XH6000 with Tornado antenna as rover and a Trimble Geo7X with Zephyr antenna as a local base station Agisoft Photoscan (v1.26) was used to make the DSM using a SfM-MVS workflow Point pairs appearing in only one image pair and havoing a reprojection error grreater than 0.5 pixels were removed Model optimization was done using default parameters of f, b1, b2, cx, cy, k1-4, p1 and p2 and, as the lens distortion plot showed no extreme skewing or distortion, these optimization settings were accepted. The dense point cloud was generated using the 'High' quality setting with 'Aggressive' point filtering. The dense point cloud was then used directly to generate the DSM and orthomosaic at resolutions of 0.046 and 0.023 m respectively. Description of files: GokyoIceCliffs_POINTCLOUD.txt: dense point cloud including the whole scene covered by the photographs. Format: x,y,z, text file, WGS 84 / UTM zone 45N. GokyoIceCliffs_DSM_0.04.tif: 0.046 m resolution digital terrain model derived from the dense point cloud covering the area of interest including the 3 sampled ice cliffs. Format: TIFF WGS 84 / UTM zone 45N. GokyoIceCliffs_ORTHO_0.04.tif: 0.023 m resolution orthophoto covering the area of interest including the 3 sampled ice cliffs. Format: TIFF WGS 84 / UTM zone 45N.本数据集包含尼泊尔Gokyo村附近的恩戈赞普冰川（Ngozumpa Glacier，27°57′N, 85°42′E）表面出露的3处冰崖的摄影测量表面模型相关数据文件。 ### 数据生成详情 1. 共使用1160张全分辨率JPEG图像构建数字表面模型（DSM, Digital Surface Model）。 2. 拍摄采用搭载100mm腾龙（Tamron）微距镜头的尼康D5000相机，拍摄时间为2016年4月4日。 3. 采用拍摄场景内的7个地面控制点（GCPs, Ground Control Points）对数字表面模型进行尺度校正与地理配准。 4. 地面控制点的测量以搭载Tornado天线的Trimble XH6000作为流动站，搭配搭载Zephyr天线的Trimble Geo7X作为本地基准站完成。 5. 使用Agisoft Photoscan（v1.26）软件，通过运动恢复结构-多视图立体匹配（SfM-MVS, Structure from Motion-Multi View Stereo）流程构建数字表面模型。 6. 剔除仅出现在单张图像对中且重投影误差大于0.5像素的点对。 7. 采用f、b1、b2、cx、cy、k1-4、p1、p2的默认参数进行模型优化；由于镜头畸变图未显示极端偏斜或畸变，故保留该优化设置。 8. 采用「高质量」模式搭配「强化」点滤波策略生成密集点云。 9. 基于该密集点云分别生成分辨率为0.046m与0.023m的数字表面模型与正射影像。 ### 文件说明 - `GokyoIceCliffs_POINTCLOUD.txt`：覆盖摄影全场景的密集点云文件，格式为包含x,y,z坐标的文本文件，坐标系为WGS 84 / UTM zone 45N。 - `GokyoIceCliffs_DSM_0.04.tif`：分辨率0.046m的数字表面模型，源自密集点云，覆盖包含3处采样冰崖的研究区域，格式为TIFF，坐标系为WGS 84 / UTM zone 45N。 - `GokyoIceCliffs_ORTHO_0.04.tif`：分辨率0.023m的正射影像，覆盖包含3处采样冰崖的研究区域，格式为TIFF，坐标系为WGS 84 / UTM zone 45N。