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Journal of Geo-information Science >

2017 , Vol. 19 >Issue 8: 1108 - 1115

DOI: https://doi.org/10.3724/SP.J.1047.2017.01108

Orginal Article

Analysis and Comparison of SRTM1 DEM and ASTER GDEM V2 Data

  • WU Wenjiao ,
  • ZHANG Shifang ,
  • ZHAO Shangmin *
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  • College of Mining Engineering, Taiyuan University of Technology, Taiyuan 030024, China
*Corresponding author: ZHAO Shangmin, E-mail:

Copy editor: 2009. , [ The Geomorphologic Atlas of the People's Republic of China Committee. The geomorphologic atlas of the People's Republic of China1:1$_$000$_$000[M]. Beijing: Science Press , 2009. ]

Received date: 2016-11-18

  Request revised date: 2017-01-01

  Online published: 2017-08-20

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《地球信息科学学报》编辑部 所有
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Abstract

Taking Shanxi Province as the research area, this paper compared the vertical accuracy of SRTM1 DEM and ASTER GDEM V2 data based on ICESat/GLA14 altimetry data. Firstly, error values for these two DEM datasets were acquired by taking ICESat/GLA14 data as the real data, and their error parameters were also calculated, such as mean error (ME), absolute mean error (AME), standard deviation (STD) and root mean square error (RMSE). Then, the error distribution of these two DEM datasets were analysed within the classes of slope, land use type and landform type. Finally, based on topographic profile method, the vertical error differences between these two DEM datasets in topographic types were analysed. The research results showed: (1) The vertical accuracy of SRTM1 DEM data is significantly higher than that of ASTER GDEM V2 data. The RMSE values of SRTM1 DEM and ASTER GDEM V2 are 6.1 m and 10.7 m, respectively. (2) Error analysis based on slope factor showed that the vertical accuracy of these two DEM datasets is affected seriously by the slope, and the error value increases with the increase of the slope value. Error analysis based on land use factor showed that the AME, STD and RMSE values of SRTM1 DEM are the lowest in paddy field, the highest in forestland, and the three error parameters of ASTER GDEM V2 are the lowest in building and the highest in forestland. Error analysis based on landform type factor showed that the AME, STD and RMSE values of SRTM1 DEM and ASTER GDEM V2 data are the lowest in the plain area, and the highest in large fluctuation mountain area. (3) On the selected topographic profiles in plain and terrace areas, the elevation value of ASTER GDEM V2 data have abnormal fluctuations. SRTM1 DEM data is too high for the estimation of valley. Overall, SRTM1 DEM is more accurate than ASTER GDEM V2 for terrain representation, which is basically consistent with ICESat/GLA14.

Key words： vertical accuracy; SRTM1 DEM; ASTER GDEM V2; ICESat/GLA14; Shanxi Province

Cite this article

WU Wenjiao , ZHANG Shifang , ZHAO Shangmin . Analysis and Comparison of SRTM1 DEM and ASTER GDEM V2 Data[J]. Journal of Geo-information Science, 2017 , 19(8) : 1108 -1115 . DOI: 10.3724/SP.J.1047.2017.01108

1 引言

数字高程模型（Digital Elevation Model,DEM）作为描述地面高程信息的基础数据,被广泛用于地形地貌、土壤、地质灾害、气候与气象和水文等研 究[1-3]。SRTM（Shuttle Radar Terrain Mission）和ASTER GDEM（Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model）是覆盖范围最广的全球免费高精度DEM数据,应用十分广泛,因此对其精度的评价至关重要。目前,对这2种DEM数据精度的评价研究已有很多,其方法主要有2种：① 与高精度的高程点对比,对其进行精度评价,如与GPS等高精度实测点[4-6]、地形图提取的高程控制点[7-9]以及ICESat等雷达测高数据[10-13]相比较;② 通过与高精度DEM数据进行比较,对其精度进行评价,如通过与大比例尺地形图生成的DEM进行对比等[14-17]。SRTM DEM的精度易受雷达后向散射的影响,地形起伏或是植被覆盖等都会影响其精度,而ASTER GDEM通过对立体影像对解译获得,其精度易受云或是地表建筑等影响[10],所以对这2种DEM数据误差的分析,主要有通过目视对比的方法、通过与高精度DEM提取的地形要素或是水文要素进行对比[17]、基于地形因子（如海拔、坡度、地形起伏度等）、土地利用类型和植被覆盖度等分析其误差的分布情况[9],或是通过提取DEM的地形剖面分析其对地形表达的准确度等[4,15]。
SRTM DEM数据之前发布的4个版本在美国境外的分辨率都是90 m,现在http://earthexplorer.usgs.gov/网站上提供了美国境外分辨率为30 m的SRTM1 DEM数据,对其精度的研究较少,所以有必要对SRTM1 DEM和分辨率为30 m的ASTER GDEM V2数据进行精度对比。而山西境内地形起伏不平,地貌类型复杂多样,因此本文利用ICESat/GLA14测高数据,对山西省境内的SRTM1 DEM和ASTER GDEM V2数据进行垂直精度的对比。基于坡度、土地利用类型和地貌类型对其误差分布进行分析,并通过提取在特定地貌类型中的地形剖面,对这2种数据对地形表达的准确程度进行分析,从而得出SRTM1 DEM数据与ASTER GDEM V2数据之间的精度对比情况,为这2种数据的更广泛应用提供一定参考。

2 研究区和数据源

2.1 研究区概况

山西省位于中国中部,东靠太行山,西依吕梁山,中有大同、忻定、太原、临汾和运城五大盆地,地理坐标为34°34′~40°43′N,110°14′~114°33′E,与河北、河南、陕西和内蒙古相邻。山西是典型的黄土覆盖的山地高原,其地势东北高西南低,大部分地区海拔达到1500 m以上,境内地势起伏不平,地貌类型复杂多样,山多川少,山地分布面积占全省总面积一半以上,平原、台地、丘陵所占面积依次减 少[18],其海拔分布见图1。
Fig. 1 SRTM1 DEM and ASTER GDEM V2 data in the study area

图1 山西省SRTM1 DEM和ASTER GDEM V2数据

2.2 数据源

ICESat/GLA14数据下载自美国国家冰雪数据中心,数据版本为34,从2003-2009年共19期数 据[19]。ICESat以Topex/Poseidon椭球体和EGM96大地水准面为参考。ICESat是监测极地冰盖质量变化、获取冰盖总量以及海平面变化的重要数据,与其他雷达测高数据相比,ICESat具有覆盖范围广、垂直分辨率高、采样密集等特点[20],其到达地面的激光脉冲可以形成约直径70 m的光斑,光斑之间距离约172 m,地面垂直精度很高,可达到15 cm左右[21],ICESat数据自发布以来得到了广泛的应用。
航天飞机雷达地形测绘使命（Shuttle Radar Topography Mission,SRTM）由美国太空总署（NASA）和国防部国家测绘局（NIMA）联合测量,由美国发射的“奋进”号航天飞机上搭载SRTM系统完成,获取了地球表面北纬60°到南纬56°之间80%以上的陆地表面雷达影像数据。SRTM地形数据按精度可以分为SRTM1和SRTM3,分别对应的分辨率精度为30 m和90 m数据,其以WGS84/EGM96为空间参考。本文使用SRTM1 Arc-Second Global（30 m）数据,下载网址为http://earthexplorer.usgs.gov/。
ASTER GDEM（先进星载热辐射和反射仪全球数字高程模型）是根据NASA的新一代对地观测卫星Terra的详尽观测结果制作完成的,数据覆盖范围为北纬83°到南纬83°之间的所有陆地区域,达到了地球陆地表面的99%,其全球空间分辨率约为30 m,垂直分辨率为20 m,空间参考为WGS84/EGM96。目前共有两版数据,第一版在2009年发布,本文研究所用数据为第二版,于2011年10月发布,ASTER GDEM V2版采用了一种先进的算法对V1版GDEM影像进行了改进,提高了数据的空间分辨率精度和高程精度。数据来源于中国科学院计算机网络信息中心地理空间数据云平台（http://www.gscloud.cn）。
土地利用类型数据通过遥感解译获得,主要采用中国科学院地理科学与资源研究所2010年所建立的土地资源分类系统。地貌类型数据来自中国1:100万数字地貌分类体系中的第1层基本地貌类型数据,是通过对Landsat的TM/ETM+遥感影像解译和GIS建库的方法,参考DEM数据和1:25万基础底图等数据,使用ArcGIS软件解译完成[22]。

3 研究方法

3.1 DEM数据和ICESat数据的处理

首先,利用NSIDC（National Snow and Ice Data Center）提供的转换工具从ICESat的原始文件中提取ICESat测高数据。ICESat测高数据采用Topex/Poseidon椭球体,而SRTM和ASTER GDEM数据是采用WGS84椭球体,WGS84椭球体和Topex/Poseidon椭球体下的高程差在70~71 cm之间,虽然这个差异随纬度变化,但变化量非常小,可以忽略。为了将ICESat测高数据、SRTM和ASTER GDEM数据统一到相同的空间参考,本文将ICESat数据的高程值减去70 cm得到WGS84椭球体下的高程值[12,23]。
然后,利用ArcGIS 10.2 3D分析中的Add Surface Information工具提取ICESat点位置对应的SRTM 和ASTER GDEM数据的高程值,以ICESat高程为标准高程值,计算2种DEM数据的垂直误差,并以±50 m为阈值,对ICESat数据进行粗差的剔除。最后一共有343 254个点参与2种DEM数据的精度评价,ICESat数据轨道见图2。
因坡度、土地利用类型和地形起伏对DEM数据的精度都有影响[6,9-10],所以基于这些因素分析DEM数据的误差分布很有必要。因此,本文分别提取剔除粗差后的ICESat点对应的坡度、土地利用类型和地貌类型（主要根据地形起伏划分）,来分析SRTM和ASTER GDEM数据的精度情况。
Fig. 2 ICESat/GLA14 data in the study area

图2 山西省ICESat/GLA14数据分布

3.2 垂直精度的评价

为了评价SRTM和ASTER GDEM数据的垂直精度,对ICESat测高数据、SRTM和ASTER GDEM数据的基本参数进行统计,统计参数包括最大值、最小值、平均值和标准偏差;然后分别对ICESat与SRTM和ASTER GDEM之间的高程差进行统计,统计参数包括平均误差、绝对误差均值、标准偏差、均方根误差,其中平均误差可以反映2种DEM数据的系统误差,绝对误差均值可以防止平均误差计算时正负相抵的情况,反应误差的绝对大小,标准偏差对于特大和特小误差非常敏感,均方根误差可以反映误差的总体大小。最后,计算2种DEM数据的误差频率分布。
基于坡度、土地利用类型和地貌类型影响因子分析SRTM和ASTER GDEM数据的垂直误差分布情况：
（1）以小于等于3°、3~8°、8~15°、15~25°和大于25°对坡度进行分级,然后基于坡度统计SRTM和ASTER GDEM数据的误差分布,并进行比较分析。
（2）以旱地、水田、草地、林地、水域、居民用地和未利用土地这7种类型分别统计SRTM和ASTER GDEM数据的误差分布。
（3）基于地形起伏度提取的地貌类型,分为平原（<30 m）、台地（30 m）、丘陵（<200 m）、小起伏山地（200~500 m）、中起伏山地（500~1000 m）和大起伏山地（1000~2500 m）,分别统计SRTM和ASTER GDEM数据在这些地貌类型中误差的分布情况。

3.3 SRTM和ASTER GDEM地形剖面的比较

通过提取DEM的地形剖面,可以分析DEM的水平位置偏差和对地形的描述误差[24-25]。根据山西省的6种基本地貌类型,分别在平原、台地、丘陵、小起伏山地、中起伏山地和大起伏山地中选取了6段ICESat轨道,如图3所示。首先将选取的ICESat轨道点转成线,然后利用ArcGIS 10.2 3D分析工具集中的Stack Profile工具分别提取SRTM和ASTER GDEM的DEM剖面,并结合ICESat的轨道剖面,分析SRTM和ASTER GDEM数据对地形描述的精度。
Fig. 3 Landform type and profile location in the study area

图3 山西省地貌类型和剖面位置

4 结果分析

4.1 SRTM和ASTER GDEM的垂直精度分析

ICESat、SRTM和ASTER GDEM高程值基本参数的统计结果见表1。从表1可看出,343 254个采样点中,ICESat的高程最小值与SRTM和ASTER GDEM相差很大,高程最大值与SRTM的高程值接近;而SRTM与ASTER GDEM的最小值相差 0.6 m,最大值相差10.5 m,ASTER GDEM的标准偏差比ICESat和SRTM大1 m。
Tab. 1 Comparison of statistical values among the ICESat, SRTM1 DEM and ASTER GDEM V2

表1 ICESat、SRTM1 DEM和ASTER GDEM V2的统计数据的比较

统计参数 数量/个 最小值/m 最大值/m 平均值/m 标准偏差/m
ICESat/GLA14 343 254 247.2 2641.2 1167.0 374.0
SRTM1 DEM 343 254 215.0 2645.1 1167.2 374.0
ASTER GDEM V2 343 254 214.4 2655.6 1167.1 375.0
Tab. 2 Error distribution of SRTM1 DEM and ASTER GDEM V2 based on slope (m)

表2 基于坡度的SRTM1 DEM和ASTER GDEM V2的误差分布（m）

统计参数 ≤3° 3~8° 8~15° 15~5° ≥25° 全部
SRTM1 DEM 平均误差 0.4 0.5 0.0 -0.1 1.0 0.2
绝对误差均值 1.4 2.7 4.3 5.3 7.6 4.0
标准偏差 2.1 3.9 5.8 7.2 10.3 6.0
均方根误差 2.2 3.9 5.8 7.2 10.4 6.1
ASTER GDEM V2 平均误差 -0.2 -0.6 -0.4 0.4 2.6 0.1
绝对误差均值 4.5 5.9 7.7 9.1 11.7 7.8
标准偏差 6.1 8.0 10.2 11.9 14.8 10.7
均方根误差 6.1 8.0 10.2 12.0 15.0 10.7
以ICESat的高程为真值,得到的SRTM和ASTER GDEM数据的垂直误差基本参数的统计结果见表2。从表2可看出,对于SRTM和ASTER GDEM,平均误差都很小,分别为0.2 m和0.1 m;绝对误差均值分别为4.0 m和7.8 m;标准偏差分别为6.0 m和10.7 m;均方根误差分别为6.1 m和10.7 m,后3种误差参数ASTER GDEM比SRTM高出4 m左右,可见在山西省内,总体上SRTM比ASTER GDEM的精度要好。2种DEM数据的误差频率分布见图4,SRTM和ASTER GDEM的误差基本呈正态分布。

4.2 基于影响因子的精度分析

（1）基于坡度的精度分析
基于坡度对SRTM和ASTER GDEM数据的误差参数的统计结果见表2。SRTM在坡度大于25°时,平均误差最大,为1.0 m,ASTER GDEM的平均误差在坡度小于15°的3个区间都是负值,在坡度大于25°时,平均误差最大,为2.6 m;SRTM在坡度小于3°时绝对误差均值、标准偏差和均方根误差都很小,分别为1.4、2.1和2.2 m,而坡度大于25°后,分别达到了7.6、10.3和10.4 m,ASTER GDEM在坡度小于3°时绝对误差均值、标准偏差和均方根误差都较小,分别为4.5、6.1和6.1 m,在坡度大于25°时,绝对误差均值、标准偏差和均方根误差分别达到了11.7、14.8和15.0 m。由此可看出,这2种DEM的精度受坡度影响很大,随坡度的升高误差增大。
（2）基于土地利用类型的精度分析
基于土地利用类型对SRTM和ASTER GDEM数据的误差参数的统计结果见表3。SRTM的平均误差在草地和居民用地为负值,在未利用地中值最大,为1.0 m;ASTER GDEM平均误差在旱地、居民用地和未利用土地中为负值,在水田中值最大,为3.2 m。SRTM的绝对误差均值随着水田、未利用地、居民用地、旱地、水域、草地和林地类型而依次增大,最小值为1.3 m,最大值为5.4 m,标准偏差和均方根误差随着水田、居民用地、旱地、水域、未利用地、草地和林地而依次增大,在水田中最小,均为1.7 m,在林地中最大,均达到了7.6 m;ASTER GDEM的绝对误差均值随着居民用地、未利用土地、旱地、水田、草地、水域和林地而依次增大,最小值为5.1 m,最大值为9.4 m,标准偏差和均方根误差随着居民用地、未利用地、旱田、水田、草地、水域和林地而依次增大,在居民用地最小,分别为6.9 m和6.9 m,在林地中最大,分别为12.4 m和12.5 m。
Tab. 3 Error distribution of SRTM1 DEM and ASTER GDEM V2 based on Land use type (m)

表3 基于土地利用类型的山西省SRTM1 DEM和ASTER GDEM V2的误差分布（m）

统计参数 旱地 水田 草地 林地 水域 居民用地 未利用地
SRTM1 DEM 平均误差 0.1 0.2 -0.1 0.7 1.0 -0.0 1.0
绝对误差均值 2.6 1.3 4.9 5.4 2.8 2.2 2.0
标准偏差 4.2 1.7 6.8 7.6 4.5 3.5 4.8
均方根误差 4.2 1.7 6.8 7.6 4.7 3.5 4.9
ASTER GDEM V2 平均误差 -1.1 3.2 0.9 1.2 0.8 -0.5 -0.6
绝对误差均值 6.6 7.1 8.5 9.4 8.7 5.1 5.8
标准偏差 9.0 10.0 11.3 12.4 12.2 6.9 8.5
均方根误差 9.0 10.5 11.3 12.5 12.2 6.9 8.5
（3）基于地貌类型的精度分析
基于地貌类型对SRTM和ASTER GDEM数据的误差参数的统计结果见表4。SRTM的平均误差在丘陵和小起伏山地中为负值,在大起伏山地值最大,为0.9 m;ASTER GDEM的平均误差在平原、台地、丘陵和小起伏山地中为负值,在大起伏山地值最大,为2.7 m。SRTM的绝对误差均值、标准偏差和均方根误差随平原、台地、小起伏山地、丘陵、中起伏山地和大起伏山地而依次增大,在平原地区,SRTM的这3种误差分别为2.0、3.4和3.5 m,而在大起伏山地这3种误差可分别达到6.3、8.9和8.9 m;ASTER GDEM的绝对误差均值、标准偏差和均方根误差都是随着平原、台地、丘陵、小起伏山地、中起伏山地和大起伏山地依次增大,在平原地区,这3种误差分别为6.2、8.6和8.6 m,而在大起伏山地,这3种误差分别达到了11.1、14.2和14.4 m。
Tab. 4 Error distribution of SRTM1 DEM and ASTER GDEM V2 based on landform type (m)

表4 基于地貌类型的山西省SRTM1 DEM和ASTER GDEM V2的误差分布（m）

统计参数 平原 台地 丘陵 小起伏山地 中起伏山地 大起伏山地
SRTM1 DEM 平均误差 0.5 0.0 -0.3 -0.2 0.6 0.9
绝对误差均值 2.0 2.9 4.5 4.4 5.6 6.3
标准偏差 3.4 4.8 6.3 6.1 7.7 8.9
均方根误差 3.5 4.8 6.3 6.1 7.7 8.9
ASTER GDEM V2 平均误差 -0.5 -0.9 -0.6 -0.2 1.6 2.7
绝对误差均值 6.2 7.1 7.5 7.8 9.6 11.1
标准偏差 8.6 9.9 10.0 10.4 12.6 14.2
均方根误差 8.6 10.0 10.0 10.4 12.7 14.4

4.3 SRTM和ASTER GDEM的地形剖面分析

基于ICESat轨道提取的SRTM和ASTER GDEM数据的地形剖面见图5。从图5可看出,位于平原地区和台地地区的地形剖面显示,SRTM和ASTER GDEM对地形的表达相差很大,ASTER出现了异常抖动,在平原地区最为剧烈,而SRTM相对比较稳定,与ICESat对地形的表达相接近;从位于丘陵地区的地形剖面可以看出,与SRTM和ICESat相比较,ASTER GDEM对地形的表达过高;从位于小起伏山地地区的剖面可以看出,ASTER GDEM数据对地形的表达比SRTM更细致,而SRTM丢失了一部分地形信息;从中起伏山地和大起伏山地地区的剖面可以看出,SRTM存在对山谷的过高估计[26-27],在这2种剖面中,ASTER GDEM和SRTM与ICESat对地形表达比较一致,在大起伏山地中3种数据一致程度最高。总体上可看出,在各种地貌类型中,与ICESat相比,SRTM比ASTER GDEM的精度要好,SRTM与ICESat对地形的表达程度较一致。
Fig. 4 Error frequency distribution of SRTM and ASTER GDEM

图4 SRTM和ASTER GDEM的误差频率分布

Fig. 5 The topographic profiles of SRTM1 DEM and ASTER GDEM V2

图5 山西省SRTM1 DEM和ASTER GDEM V2的地形剖面图

5 结论

本文通过利用高精度的ICESat/GLA14雷达测高数据,对山西省的SRTM1 DEM和ASTER GDEM V2数据进行垂直精度的对比分析,得出以下结论：
（1）在山西省境内,SRTM1 DEM和ASTER GDEM V2数据的总体平均误差分别为0.2 m和0.1 m,绝对误差均值分别为4.0 m和7.8 m,均方根误差分别为6.1 m和10.7 m, SRTM1 DEM数据的垂直精度明显高于ASTER GDEM V2数据。山西山地和丘陵居多,地势起伏大,对于平原为主的地区,这2种DEM数据的质量可能会优于本文的结果。
（2）SRTM1 DEM和ASTER GDEM V2数据的垂直精度受坡度、土地利用类型和地貌类型影响严重。坡度越大,数据精度越差,在坡度大于25°后,SRTM1 DEM的均方根误差达到了10.4 m,而ASTER GDEM V2达到了15.0 m;由于SRTM1 DEM和ASTER GDEM V2数据的生成原理不同,其数据质量受地类影响也不同,SRTM1 DEM的均方根误差在水田最小,ASTER GDEM V2的均方根误差在居民用地最小,而且ASTER GDEM V2数据在水域的误差较大,这2种数据受植被覆盖的严重影响,在林地的精度最差;SRTM1 DEM 和ASTER GDEM V2数据在平原地区精度最好,随地形起伏的加剧,误差逐渐增大;从提取的地形剖面可以发现,ASTER GDEM V2数据存在较多异常的高程值,在较平坦的平原或台地地区,高程异常的波动非常明显,对于地形表达的准确性比SRTM1 DEM数据差。
（3）本文对SRTM1 DEM和ASTER GDEM V2数据精度的分析以及误差分布情况的分析结果可以为这2种DEM数据的应用提供一定参考。应用DEM数据时应考虑其所属区域的地形、地类和地貌特征对数据质量的影响,不同的地形、地类和地貌数据精度差异很大,对于地势平坦的地区,使用SRTM1 DEM数据可能更为可靠。

The authors have declared that no competing interests exist.

References

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DOI

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DOI

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[19]
Phan V H, Lindenbergh R, Menenti M.ICESat derived elevation changes of Tibetan lakes between 2003 and 2009[J]. International Journal of Applied Earth Observation and Geoinformation, 2012,17:12-22.The Tibetan plateau contains thousands of small and big lakes. Changes in the water level of these lakes can be an important indicator for the water balance of the Tibetan plateau, but were until now extremely difficult to monitor: performing continuous in situ measurements at a large number of lakes is not feasible because of their remoteness, while radar altimetry is only capable of monitoring large lakes. Between 2003 and 2009 the Geoscience Laser Altimeter System (GLAS) on board of the Ice, Cloud and land Elevation Satellite (ICESat) obtained world-wide elevation profiles during 18 one-month campaigns. Using the GLAS data it is possible to obtain lake levels at decimeter accuracy. Available GLAS data over the Tibetan lakes is selected by means of the MODIS lake mask. As a result, lake level variations between 2003 and 2009 of 154 lakes of over a square kilometer size could be observed. For these lakes, an analysis of annual water level trends is made, and then their yearly gained or lost water volumes are estimated. In total, an area averaged increase in lake level of 0.20m/year over the Tibetan plateau is observed between 2003 and 2009. Most of the individual lakes considered in this paper have little or no levels apparently documented, and so the ICESat data provide the first baseline measurements of these lakes in the vertical.

DOI

[20]
Zwally H J, Schutz R, Abdalati W, et al.ICESat’s laser measurements of polar ice, atmosphere, ocean, and land[J]. Journal of Geodynamics, 2002,34(3-4):405-445.The Ice, Cloud and Land Elevation Satellite (ICESat) mission will measure changes in elevation of the Greenland and Antarctic ice sheets as part of NASA's Earth Observing System (EOS) of satellites. Time-series of elevation changes will enable determination of the present-day mass balance of the ice sheets, study of associations between observed ice changes and polar climate, and estimation of the present and future contributions of the ice sheets to global sea level rise. Other scientific objectives of ICESat include: global measurements of cloud heights and the vertical structure of clouds and aerosols; precise measurements of land topography and vegetation canopy heights; and measurements of sea ice roughness, sea ice thickness, ocean surface elevations, and surface reflectivity. The Geoscience Laser Altimeter System (GLAS) on ICESat has a 1064 nm laser channel for surface altimetry and dense cloud heights and a 532 nm lidar channel for the vertical distribution of clouds and aerosols. The predicted accuracy for the surface-elevation measurements is 15 cm, averaged over 60 m diameter laser footprints spaced at 172 m along-track. The orbital altitude will be around 600 km at an inclination of 94掳 with a 183-day repeat pattern. The on-board GPS receiver will enable radial orbit determinations to better than 5 cm, and star-trackers will enable footprints to be located to 6 m horizontally. The spacecraft attitude will be controlled to point the laser beam to within卤35 m of reference surface tracks at high latitudes. ICESat is designed to operate for 3-5 years and should be followed by successive missions to measure ice changes for at least 15 years.

DOI

[21]
文汉江,程鹏飞. ICESAT/GLAS激光测高原理及其应用[J].测绘科学,2005,30(5):33-35.本文介绍了ICESAT卫星的基本工作原理,对该卫星上的地学激光测高系统GLAS的测量原理和精度进行了分析,通过GLAS可获得冰原地形及其时变,同时也可对云及大气层的特征有更深入地了解。对GLAS的适用于冰原、冰面、陆地以及海面波形的算法进行了分析,简单介绍了对GLAS测高数据进行检核和校准,并对ICESAT数据在地学研究中的应用进行了探讨。

DOI

[ Wen H J, Cheng P F.Introduction to principle of ICESAT/GLAS laser altimetry and its applications[J]. Science of Surveying and Mapping, 2005,30(5):33-35. ]

[22]
中华人民共和国地貌图集编辑委员会.中华人民共和国地貌图集(1:1 000 000)[M].北京:科学出版社,2009.

[ The Geomorphologic Atlas of the People's Republic of China Editor Committee. The geomorphologic atlas of the People's Republic of China (1:1 000 000) [M]. Beijing: Science Press, 2009. ]

[23]
Bhang K J, Schwartz F W, Braun A.Verification of the vertical error in C-band SRTM DEM using ICESat and Landsat-7, Otter Tail County, MN[J]. IEEE Transactions on Geoscience and Remote Sensing, 2007,45(1):36-44.The Shuttle Radar Topography Mission (SRTM) provided scientists with digital elevation data on a nearly global scale and with highly consistent accuracy. This paper compares elevation values of the C-band SRTM 30-m digital elevation model (DEM) with pointwise elevations from the Ice, Cloud, and land-Elevation Satellite (ICESat) laser altimetry for Otter Tail County, Minnesota. The accuracy of SRTM DEM is measured as a function of land covers and geomorphologic characteristics. The typical mean vertical difference between the SRTM DEM and ICESat elevations in this paper was determined in each classified land-use type and is approximately 1.5 m over bare ground, with the SRTM measuring lower elevations. Significant changes in the SRTM DEM uncertainties have been identified over different surface types classified from Landsat-7 imagery, e.g., bare ground, urban, and forested areas. Based on this result, the difference of the SRTM 30-m DEM and ICESat elevations has been removed from the DEM and made available for improved hydrological applications

DOI

[24]
郭笑怡,张洪岩,张正祥,等. ASTER GDEM 与SRTM3 数据质量精度对比分析[J].遥感技术与应用,2011,26(3):334-338.ASTER-GDEM是最新的全球数字高程模型,具有较高的分辨率；SRTM3是目前研究人员广泛应用的地形数据。结合实测数据、矢量化地形图,从高程精度、位置精度和坡度因子3方面对比分析两种数据精度。结果表明:ASTER-GDEM数据高程精度低于SRTM3数据,而水平位置精度较高,二者各级坡度百分率近似,与国家1∶5万数字地形图生成的DEM差异较大。

[ Guo X Y, Zhang H Y, Zhang Z X, et al.Comparative analysis of the quality and accuracy between ASTER. GDEM and SRTM3[J]. Remote Sensing Technology and Application, 2011,26(3):334-338. ]

[25]
Nikolakopoulos K G, Kamaratakis E K, Chrysoulakis N.SRTM vs ASTER elevation products. Comparison for two regions in Crete, Greece[J]. International Journal of Remote Sensing, 2006,27(21):4819-4838.The Shuttle Radar Topography Mission (SRTM) collected elevation data over 80% of earth's land area during an 11‐day Space Shuttle mission. With a horizontal resolution of 3 arc sec, SRTM represents the best quality, freely available digital elevation models (DEMs) worldwide. Since the SRTM elevation data are unedited, they contain occasional voids, or gaps, where the terrain lay in the radar beam's shadow or in areas of extremely low radar backscatter, such as sea, dams, lakes and virtually any water‐covered surface. In contrast to the short duration of the SRTM mission, the ongoing Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is continuously collecting elevation information with a horizontal resolution of 1502m. In this paper we compared DEM products created from SRTM data with respective products created from ASTER stereo‐pairs. The study areas were located in Crete, Greece. Absolute DEMs produced photogrammetricaly from ASTER using differentially corrected GPS measurements provided the benchmark to infer vertical and planimetric accuracy of the 3 arc sec finished SRTM product. Spatial filters were used to detect and remove the voids, as well as to interpolate the missing values in DEMs. Comparison between SRTM‐ and ASTER‐derived DEMs allowed a qualitative assessment of the horizontal and vertical component of the error, while statistical measures were used to estimate their vertical accuracy. Elevation difference between SRTM and ASTER products was evaluated using the root mean square error (RMSE), which was found to be less than 5002m.

DOI

[26]
Hayakawa Y S, Oguchi T, Zhou L.Comparison of new and existing global digital elevation models: ASTER G-DEM and SRTM-3[J]. Geophysical Research Letters, 2008,35(L17404):1-5.A new global elevation dataset known as G-DEM, based on the ASTER satellite imagery, will be released in late 2008. G-DEM will be the best freely available global digital elevation model (DEM) at a horizontal resolution of 1 arc second. We assess the quality of G-DEM in comparison with 3-arc-second SRTM DEM, the best current global elevation dataset. Basic geomorphometric parameters (elevation, slope and curvature) were examined for a pre-release version of G-DEM and SRTM DEM for western Japan. G-DEM has fewer missing cells than SRTM DEM, particularly in steep terrain. Also, G-DEM gives smoother and more realistic representations of lowlands, valleys, steep slopes, and mountain ridges, whereas, SRTM DEM includes many local spikes and holes, and tends to overestimate valley-floor elevation and underestimate ridge elevation. G-DEM will be commonly used in geoscientific studies, because of its higher resolution, fewer missing data, and better topographic representation than SRTM DEM.

DOI

[27]
陈俊勇. 对SRTM3和GTOPO30地形数据质量的评估[J].武汉大学学报·信息科学版,2005,30(11):941-944.高分辨率的地形数据在基础地理信息系统、地球重力场建模和大地水准面求定等工程中至关重 要.SRTM有3″×3″(SRTM3)和1″×1″(SRTM1)两种分辨率.就全球而言,SRTM3的原始数据已于2004年解密.SRTM3的高程 基准是EGM96的大地水准面,平面基准是WGS84;标称绝对高程精度是±16 m,绝对平面精度是±20 m.SRTM3的数据只覆盖60°N至54°S带状区域内的DSM.对覆盖全球的GTOPO30的DTM也作了概要介绍.

DOI

[ Chen J Y.Quality evaluation of topographic data from SRTM3 and GTOPO30[J]. Geomatics and Information Science of Wuhan University, 2005,30(11):941-944. ]

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