基于DEM提取水域特征的一种算法实现_图文

1、第32卷第1期2007年1月测绘科学Science of Surveying and M app ingVol 132No 11Jan 1 作者简介:李勤超(1982 ,男,湖北天门人,解放军信息工程大学测绘学院六系三队450052,硕士生,主要从事地理信息系统研究。E mail:poll_lenyahoo 1com 1cn收稿日期:20060316基于D E M 提取水域特征的一种算法实现李勤超,李宏伟,孟婵媛(解放军信息工程大学测绘学院,郑州450052;海军海洋测绘研究所,天津300061【摘要】本文提出并实现了一种基于规则格网DE M 的地形特征线提取算法。该算法基于水文模拟方法,提出

2、了平地、洼地的结构模型,研究了它们形成复杂洼地的拓扑关系,在此基础上设计了洼地填平等算法,简便快捷,在邙山小流域水土保持项目中得到应用,效果较好。【关键字】格网DE M;水文模拟;地形特征;水域特征【中图分类号】P282【文献标识码】A 【文章编号】10092307(2007010103021引言河流水系的提取技术被广泛应用于地图制图、水文模拟和地质灾害预测等众多研究领域。传统的人工方法不仅费时费力,而且由于水系级别的人为确定和低级别水流线的删除等问题,造成了许多误差。近年来,随着地理信息系统(GI S 的日益普及,特别是能够表达丰富地貌信息的数字高程模型(DE M 技术的出现,使从DE M

3、中提取地貌特征信息成为一项重要的研究工作。中外学者提出了许多自动提取的方法,并开发了相关的软件。根据算法设计的原理,从DE M 中自动提取水系网络的方法主要分为三类1:基于地形表面几何形态的方法,也称之为局部方法,如Johnst on 和Rosenfeld 等的地形方向断面极值法,以及Tribe 的河谷网络算法,该方法提取的河流网络,存在河流结点的不连续性以及河流源头定位的随意性等问题;基于地表水流模拟的方法,也称之为全局方法,它首先给每个DE M 单元赋流向,然后根据所有单元的流向产生一个全连接的、单个单元宽度的流向网络,最后根据集水区识别河流网络;对DE M 单元赋流向是根据水流向最低的物

4、理原理,包括D8、Rho8、DE MON 以及D 等方法,其中最具代表性的是D8法,简单快捷,且依据水流的物理原理和水文学模型,具有重要的实用价值,本文即表述了基于该算法的一种实现;基于局部方法和全局方法的复合方法,它是在全局径流一致性的基础上,考虑到局部地貌的特殊性而采取的一种加权方法,使提取的水系与实际河流更好地拟合。但该方法具有很强的针对性,因此其适用性受到限制。2水文模拟算法的原理基于地表水流模拟的地形特征提取算法基本原理是2:根据地表水流从高处流向低处的自然规律,计算DE M 中每一单元的汇水量,可以认为汇水量大于某个阈值的单元属于汇水线,如果将这些汇水量大于给定阈值的离散点,按规则

5、连接起来就可以将汇水线即山谷线提取出来。该原理的关键是3个矩阵的生成:填平原始DE M 中的洼地生成无洼地高程矩阵;在无洼地高程矩阵基础上计算水流方向矩阵;在水流方向矩阵基础上计算水流累积矩阵。在实际提取过程中,因在填平洼地时用到了每个单元的水流方向信息,所以应先计算水流方向矩阵。在得到上述3个矩阵后,即可进行地形特征或水文特征提取、汇水区域计算等分析,算法的流程图(见图1。图1水文模拟算法流程本文采用D8算法计算单元水流方向,即根据DE M 栅格单元和八邻域单元之间的最大坡降来确定水流方向,文献3等都有详述。本文的重点是洼地填平算法的设计。3模型建立与算法设计朱庆、赵杰4等曾提出在水文模拟方

6、法的基础上,提取洼地的一些矢量特征,将矢量操作与栅格操作结合起来对DE M 中的洼地进行处理。本文即是受此启发,将洼地、平地都抽象为矢量对象,并更深入讨论了它们之间的关系,在此基础上设计了洼地填平等操作,算法具体步骤如下:首先基于栅格操作,得到每个单元的流向,检测出平地与洼地并提取其矢量特征;然后将平地与洼地构建为矢量对象,操作这些对象完成洼地填平步骤;对于矢量平地对象,再将其化为栅格单元,利用矢量特征出流点,按规则给其每个单元赋流向,最终得到水文特征分析所要的水流方向矩阵。在上述操作基础上完成河网提取(汇水能力阈值取用平均水流累计值和流域划分。311基本对象结构平地、洼地的结构如图2:图2平

7、地(a、洼地(b结构图 按照D8算法,我们将根据每个单元的流向赋值(如图3,得到初始方向矩阵。在原始DE M 数据源中,存在许多无法给DE M 单元赋流向的情况(周围单元比中心单元高或等高,此时将其值赋为0,称这些点为零点。从这些零点出发,采用种子算法5,可以检测出平地与洼地,这里不再赘述。将检测出来的平地、洼地按上图中的结构进行组织、存储。其中edge 为边缘点,fl owpoint 为出流点,bott om 则是洼地中的零点集合。需要指出的是,平地、洼地的出流点的意义并不同,前者指平地边缘点中有最大坡降的点,后者则是洼地边缘点中高程值最小的点,且两者可能都不唯一。对于洼地来说,要求执行填平

8、操作后形成平地。312对象关系对于简单的洼地,将洼地中高程值小于其出流点高程的单元用出流点高程代替即可形成平地,生成平地的出流点应出自原洼地的出流点。如果某一洼地的出流点同时是别的洼地或平地的边缘点,情况就复杂许多。比如洼地出流点是一平地边缘点,可将洼地填平并直接与此平地合并,生成新平地。问题的关键在于洼地出流点的状态,所以在洼地、平地的检测同时还要记录下其出流点状态。本文从简化的情况开始,在洼地只有一个出流点的假设下,分别讨论两个洼地以及一个洼地与一个平地的关系。若两个洼地共享唯一出流点,两个洼地可分别填平并合并:若在此点两洼地存在互指关系,即在出流点水流方向相互指向了对方,则填平合并后的部

9、分将还在洼地内,且是新洼地bott om 部分;否则,填平合并后将形成平地,而且由于在出流点周围可能存在与其高程相等的点,平地还可能在此处扩张。需要指出的是所谓呈环状指向的复杂洼地,可归于相邻洼地互指的情况。如图4,设洼地D 1、D 2、D 3的出流点高程分别为h 1、h 2、h 3。出流点是洼地边缘点中高程最小的点,D 1的出流点指向了D 2,应是D 1、D 2的边缘点,所以有h 1h 2。依次类推,有h 1h 2h 3h 1,所以h 1=h 2=h 3,即D 1与D 2、D 1与D 3、D 2与D 3都应是互指的关系 。若洼地出流点在平地边缘,显然洼地填平后可与平地合并,生成新平地,且将继

10、承原平地的出流点。313填平算法设计与实现考虑复杂洼地的合并及平地的扩张均是在洼地出流点发生,而新并入的洼地或平地可能带来更多地出流点,本文设计了如下迭代算法用于填平洼地:搜索、考察洼地每一个出流点状态,符合上一小节合并条件的,合并相应的洼地或平地;对于并入的洼地,继续按上述方法处理其出流点;对于并入的平地,搜索、考察其边界点,判断其是否为其他洼地出流点,即是否满足上节条件,作相应处理;在洼地出流点处,满足上节条件的,还应作扩散处理(按洼平地检测时使用的种子算法。在实际操作中还有更复杂的情况,如两洼地共用的出流点是平地边界点等,依然可套用上述算法。将上面的步骤迭代进行,直至洼地形成独立的平地;

11、所有洼地都执行此操作,即可完成水文模拟算法的填洼过程。314平地水流方向确定针对平地水流方向问题很多研究者提出了不同的方法:Martz 和Garbrecht 的微地貌起伏算法,对平地单元高程增加不同微量直至每个单元都有一个明确的水流方向;Tribe 提出了一种汇聚模式的赋流向方法,使河流在平原区内通过的距离最短;Jens on 的方法是从出水口出发首先确定与出口点相邻的平地点的流向,然后处理这些点的邻域点,如此迭代直到整个平地内所有点都被赋予流向。朱庆等对这些方法进行了比较4,提出了利用平地失量模型,从提取的出流点开始,由近至远随机选择相邻单元进而标定整个平地流水方向,使其汇聚于出流点,方便快

12、捷,还能有效消除平行和锯齿,本文即是采用此法。4应用结果本算法成功应用于邙山小流域水土保持应用系统,利用获得的邙山小流域DE M 数据(1131453278°1131622111°E 、341824191°341886296°N 、5m 精度,共3776行×1408列,面积95177k m 2进行了河网提取和流域划分(图5 。图5邙山小流域河网提取、流域划分结果图从图5可看出河网提取和流域划分结果较好的匹配了原始DE M 影像。该算法在其他小流域的适用性有待进一步验证。5结论本文提出了洼地、平地矢量结构模型,讨论了它们之间关系,以面向对象的思想

13、设计了洼地填平以及平地水流方向确定的算法,与以往算法相比速度更快,也更客观,并且在邙山小流域水土保持应用系统中运用,取得较好的成果。参考文献1徐涛,胡光道1基于数字高程模型自动提取水系的若干问题J .地理与地理信息科学,2004,20(5:111412汤国安,刘学军,闾国年1数字高程模型及地学分析的原理与方法M .北京:科学出版社,200513李志林,朱庆1数字高程模型M .武汉:武汉大学出版社,200114朱庆,赵杰,钟正1基于规则格网DE M 的地形特征提取算法J .测绘学报,2004,33(1:778215周贵云,刘瑜,邬伦1基于数字高程模型的水系提取算法J .地理学与国土研究,2000

14、,16(4:778116易红伟,汤国安,刘咏梅1河网径流节点及其基于DE M 的自动提取J .水土保持学报,2003,17(3:10811117任立良,刘新仁1数字高程模型信息提取与数字水文模型研究进展J .水科学进展,2000,11(4:4634691401测绘科学第32卷technique in visual studi o1net,takes Taihu lake watershed as a study area in order t o establish an unified,efficient and reliable sys2 te m f or data sharing1Th

15、e data sharing syste m p r ovides a great deal of data f or comp rehensive manage ment of Taihu lake watershed,and benefits f or the devel opment of the watershed1Key words:Taihu lake watershed;s mart client;data sharing; syste m i m p lementati on;FEN G L i,L I U X iao m ei,HE B aojing(Depart m ent

16、 of U rban and Res ources Sciences,Nanjing University,Nanjing 210093,China;Nanjing I nstitute of geography and li m nol ogy, CAS Nanjing210008M erg i n g ASTER w ith T M/ET M+da t a to m on itor l and cover changeAbstract:Monit oring landuse and landcover change usually u2 ses high s patial res olut

17、i on i m ages,such as I K ONOS,QU I CK B I RD or SP OT51I n this paper,taking Haidian district f or exa mp le,the au2 thors merge ASTER with T M/ET M+median res oluti on i m ages by B r ovey transfor m and p rinci pal co mponent analysis(PC Amethods, atte mp ting t o make full use of multis pectral

18、and higher s patial res olu2 ti on characteristic of ASTER and T M/ET M+i m ages,even t o m ine their potential which can be used in landuse and landcover change1 This paper may p r ovide scientific reference for cos m ically monit oring landuse and landcover change1The authors have merged multis pe

19、ctral(bands3N,2,1ASTER i m age of2003with panchr o matic ET M+i m age of1999using B r ovey transf or m Method,and fused T M543col or co mpositi on i m ages of1992with ET M+P AN of1999by PC A method,finally,as a result,both fusi on i m ages can sho w change clearly1By tested,the p recisi on of change

20、 inf or mati on detecti on ar2 rived92150%,which accords with the de mand of app licati on1I n this study,the result sho ws that cheaper ASTER and T M/ET M+data fu2 si on may efficiently monit or landcover change,es pecially in the re2 gi on without high res oluti on data,which can save the cost of

21、dyna m ic monit oring1Mean while,it indicates that ASTER and T M/ET M+i m2 ages have large utility value,and deserve extensive use1Key words:ASTER;T M/ET M+;br ovey transf or m;PCA; landcover changeHE Fenqin,HU Z henqi,Y I N J ianzhong,FAN G Sh i bo(I nstitute of Land Reclamati on and Ecol ogical Re

22、st ora2 ti on,China University ofM ining and Technol ogy,Beijing100083, China;State Key Laborat ory of I nf or mati on Engineering in Sur2 veying,M app ing and Remote Sensing,W uhan University,W u2 han430079,China;I nstitute of Botany,CAS,Beijing 100093,ChinaThe software m ethods rea li za ti on to

23、i m prov i n g rea lti m e re2 spon se i n e m bedded G I SAbstract:Due t o comp rehensive app licati on,it is very signifi2 cant t o research realti m e res ponse about e mbedded GI S1After choo2 sing an e mbedded CP U,there are s ome s oft w are methods t o i m p r ove realti m e res ponse1Map s p

24、ace data organizing structure,double buffer technique,s pecial arithmetic of drawing map sy mbols,etc are described in details in this article1Testing indicates that these ways are very effective1Key words:e mbedded GI S;realti m e res ponse;bl ocked and graded s pace data architecture;double buffer

25、 technique1HU Zem ing,YU E Chunsheng,WAN G Zhigang(I nfor ma2 ti on Engineer University,Zhengzhou in Henan Pr ovince,450002Syste m desi gn of veh i cle i n forma ti on manage m en t pl a tfor m and its key technology ana lysisAbstract:This paper is mainly about the infor mati on manage2 ment of vehi

26、cles based on GPS l ocati on infor mati on1Firstly,it gives the syste m design of vehicle inf or mati on trace and manage ment1 Then,it analyzes the relative key technol ogies1Finally,it gives the effective exa mp le and its perf or mance analysis1Key words:moving objects l ocati on;GPRS;W eb Servic

27、es; COM+;database connecti on poolHUAN G Guangyu,SHEN Zhanfeng,LUO J ianchengSHEN G Hao(School of the Earth Sciences and Res ources,Chi2 na University of Geosciences,Beijing100083,China;I nstitute of Re mote Sensing App licati ons,Chinese Acade my of Sciences,Beijing 100101,ChinaAn a lgor ith m for

28、extracti n g wa tershed fea tures ba sed on D E M Abstract:This paper p resents an algorith m f or watershed fea2 tures extracti on based on DE M1On the basis of hydr ol ogy si m ulati on algorith m,we p r opose a structural model of the dep ressi ons and flats,and study the t opol ogical relati ons

29、 when f or m ing the comp lex dep ressi ons1Then we design an algorith m t o fill dep ressi ons1This app r oach has been used in the p r oject of water and s oil p reservati on in Mangshan s mall watershed1And the result p r oves its efficiency and convenience1Key words:grid DE M;hydr ol ogy si m ul

30、ati on;t opographic fea2 ture;watershed featureL I Q inchao,L I Hongw ei,M EN G Chanyuan(I nsti2 tute of Surveying and Mapp ing,I nf or mati on Engineering University, Zhengzhou450052,China;Naval I nstitute of Hydr ographic Sur2 veying and Charting,Tianjin300061,ChinaPositi on and area prec isi on s

31、tudy of Spot5i m age correcti on i n urbanAbstract:I n order t o p r obe the positi on and area p recisi ons of the SP OT5i m age corrected with2D polynom ial in urban regi on,dif2 ferent p recisi on(acquired fr om GPS field surveying and1:10000 t opography mapand nu mber(25and6of gr ound contr ol p

32、oints (GCPswere used t o correct the SP OT5i m age with2D polynom ial functi on res pectively110GPS points were used as check points (CPst o test the positi on and area p recisi on of f our results1The conclusi ons were dra wn that:(1For urban SP OT5i m age,thr ough 2D2sd polynom ial functi on using

33、6high p recisi on GPS GCPs,better positi on p recisi on could be obtained1(2Satisfied positi on p recisi on could be reached using1:10000t opography map if GCPs are e2 nough and l ocati on of the m is well distributed1(3Satisfied area p recisi on could be reached on the i m ages corrected by GPS CPs

34、 and map CPs and that is enough for urban green s pace syste m surveying1 (4The relati onshi p bet w een positi on and area err ors is comp lex on the corrected i m ages,s o the area err ors cannot be deduced by point err ors according t o theory of err ors1Key words:RS;SP OT5;geometric correcti on;

35、point and area p recisi onFEI X ianyun,ZHANG Zhiguo,G AO X iangwei,Q I U J ianzhuang(College of I nf or mati on Science and Engineering, Shandong Agricultural University,Taian,271018;College of Re2 s ources and Envir on ment,Shandong Agricultural University,Taian, 271018;I nstitute of Land Recla mat

36、i on and Ecol ogical Reconstruc2 ti on,China University ofM ining and Technol ogy,Beijing100083The appli ca ti on of3D Zern i ke m o m en ts i n3D terra i n ma tch i n g Abstract:I n this paper the theory of matching research of3D terrain are given firstly1Then the definiti on of3D Zernike mo ments

37、is intr oduced1A3D terrain matching alg orith m based on3D Zernike mo2 ments is pr oposed1The i m p le mentati on of this alg orith m is presented1 Finally,as is revealed by our study,the alg orith m based on the3D Zernike mo ments is a mong the most successful technique at p resent1 Key words:3D te

38、rrain surface;3D Zernike mo ments;terrain matchingHU X iulin,CHE L ong,YE B in(Dep t1of E1I1,Huazhong University of Science and Technol ogy,W uhan430074,ChinaA lgor ith m s of shortest pa th for ra ster network ba sed on map a l2 gebraAbstract:The status quo of net w ork analysis and algorith m s of shortest path is discussed in this paper firstl