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.