With the advent of very high-resolution(VHR)imaging satellites,it is possible to measure the heights of forest stands or even individual trees more accurately.However,the accurate geometric processing of VHR images de...With the advent of very high-resolution(VHR)imaging satellites,it is possible to measure the heights of forest stands or even individual trees more accurately.However,the accurate geometric processing of VHR images depends on ground control points(GCPs).Collecting GCPs through fieldwork is time-consuming and labor-intensive,which presents great challenges for regional applications in remote or mountainous regions,particularly for international applications.This study proposes a promising approach that leverages GF-7 VHR stereoscopic images and Google Earth’s multi-temporal historical imagery to accurately extract forest heights without the need for fieldworks.Firstly,an algorithm is proposed to collect GCPs using Multi-temporal Averaging of historical imagery provided by Google Earth(GE),known as MAGE.Digital surface model(DSM)is then derived using GF-7 stereoscopic imagery and MAGE GCPs in Switzerland.Forest heights are finally extracted by subtracting ground surface elevations from GF-7 DSM.Results show that absolute coordinate errors of MAGE GCPs are less than 2.0 m.The root mean square error(RMSE)of forest heights extracted from GF-7 DSM,derived using the original geolocation model,is 12.3 m,and the determination coefficient(R^(2))of linear estimation model is 0.72.When the geolocation model is optimized using MAGE GCPs,the RMSE is reduced to 1.5 m and the R^(2)increases to 0.95.These results not only demonstrate the effectiveness of MAGE GCPs but,more importantly,also reveal the significance of precise geometric processing of VHR stereoscopic imagery in forest height estimations.展开更多
Explaining fundamentals of application of cable bolting for a thick seam depillaring,this paper summarizes the results of field studies conducted during adoption of this approach in more than fifteen panels of Madhusu...Explaining fundamentals of application of cable bolting for a thick seam depillaring,this paper summarizes the results of field studies conducted during adoption of this approach in more than fifteen panels of Madhusudanpur 7 pit and incline mine.Nearly 7.0 m thick Kajora top coal seam of this mine is developed on pillars along the floor horizon to an average height of 3.0 m,leaving a coal band of around 4.0 m along the roof.Analysis of procured core samples showed that roof strata are easily caveable with a caveability index value of around 2000 only.Easily caveable overlying strata and shallow depth of cover alleviated most of the expected strata mechanics problems of the thick seam mining.However,extraction of total thickness at shallow cover caused differential-subsidence and cracks on the surface.These manifestations were immediately tackled to avoid creation of a breathing path for spontaneous heating in the extracted area.展开更多
基金sponsored by the National Natural Science Foundation of China(Grant Nos.42022009 and 42090013)the National Key Research and Development Program of China(2020YFE0200800).
文摘With the advent of very high-resolution(VHR)imaging satellites,it is possible to measure the heights of forest stands or even individual trees more accurately.However,the accurate geometric processing of VHR images depends on ground control points(GCPs).Collecting GCPs through fieldwork is time-consuming and labor-intensive,which presents great challenges for regional applications in remote or mountainous regions,particularly for international applications.This study proposes a promising approach that leverages GF-7 VHR stereoscopic images and Google Earth’s multi-temporal historical imagery to accurately extract forest heights without the need for fieldworks.Firstly,an algorithm is proposed to collect GCPs using Multi-temporal Averaging of historical imagery provided by Google Earth(GE),known as MAGE.Digital surface model(DSM)is then derived using GF-7 stereoscopic imagery and MAGE GCPs in Switzerland.Forest heights are finally extracted by subtracting ground surface elevations from GF-7 DSM.Results show that absolute coordinate errors of MAGE GCPs are less than 2.0 m.The root mean square error(RMSE)of forest heights extracted from GF-7 DSM,derived using the original geolocation model,is 12.3 m,and the determination coefficient(R^(2))of linear estimation model is 0.72.When the geolocation model is optimized using MAGE GCPs,the RMSE is reduced to 1.5 m and the R^(2)increases to 0.95.These results not only demonstrate the effectiveness of MAGE GCPs but,more importantly,also reveal the significance of precise geometric processing of VHR stereoscopic imagery in forest height estimations.
基金sponsored by the general manager,Kajora Area of Eastern Coalfield Limited(ECL).Co-operation of general manager of the Area,project officer,Madhusudanpur 7 Pit and Incline Colliery,manager and safety officer,Madhusudanpur 7 Pit and Incline Colliery in conducting this study is thankfully acknowledged
文摘Explaining fundamentals of application of cable bolting for a thick seam depillaring,this paper summarizes the results of field studies conducted during adoption of this approach in more than fifteen panels of Madhusudanpur 7 pit and incline mine.Nearly 7.0 m thick Kajora top coal seam of this mine is developed on pillars along the floor horizon to an average height of 3.0 m,leaving a coal band of around 4.0 m along the roof.Analysis of procured core samples showed that roof strata are easily caveable with a caveability index value of around 2000 only.Easily caveable overlying strata and shallow depth of cover alleviated most of the expected strata mechanics problems of the thick seam mining.However,extraction of total thickness at shallow cover caused differential-subsidence and cracks on the surface.These manifestations were immediately tackled to avoid creation of a breathing path for spontaneous heating in the extracted area.
