cwp軟件操作手冊版5p

1、CWF軟件的安裝在LINUX下建立用戶CWP在CWPF建立目錄path，將源文件放二. 到path目錄下，并建立bin文件夾三. 在CWP用戶主目錄下顯示隱藏文件，修改.bash_profile 文件，在已有的export之后另起一行，分別添加export CWPROOT二/home/CWP/path 再于PATH=$PATH:$HOME/bi 后添力口:/home/CWP/path/bin:/home/CWP退出保存四. 從終端中分別輸入cd path待終端中反映完畢，分別輸入cd srcmake in stallmake xti nstallmake mgli nstallmake uti

2、lsmake xmi nstallmake sfin stall這期間可能有系統(tǒng)安裝所等待的時間，不用急，但凡遇到y(tǒng)es/no，路y下來即可。四為了檢查是否安裝完畢，在終端中輸入Supla ne > data.suSuxwigb < data.su &若出現(xiàn)一個簡單的圖像，則成功！CW軟件的簡單說明一、 文中涉及的命令全部以 小寫形式，均可在終端窗口下輸入，以次獲取 自述幫助。先說幾個命令：suplane和suxwigb， more。suplane作用是產(chǎn)生一個簡單的零偏移距su文件，suxwigb是一個典型的X windows繪制圖形工具，如例子：supla ne >

3、; data.susuxwigb < data.sumore < data.su比較全面的了解它們，請在終端中輸入supla ne , suxwigb ,more 。二、關(guān)于DEMOS勺應(yīng)用 所有DEMO必須把文件拷到用戶根目錄下，而后 依照readme文件中的執(zhí)行順序，在終端中輸入文件名。注意目錄下的文件變動。三、在執(zhí)行DEMO文件時，如果想清楚了解程序執(zhí)行過程，請輸入more progra mn ame由于水平有限，這里的謬誤很多，希望大家能在偶爾翻看時，多多留心，發(fā)現(xiàn)并改正，衷心希望能和大家一起學(xué)習(xí)。謝謝第一節(jié)兩種數(shù)據(jù)的轉(zhuǎn)換在CWP應(yīng)用中免不了和兩種數(shù)據(jù)打交道，su和segy

4、格式。它們有聯(lián)系也有 區(qū)別一.數(shù)據(jù)的輸入輸出1讀寫編輯數(shù)據(jù)常用命令如下：segyread-read an SEG-Y tape segywite-write an SEG-Y tapesegyclea n zeor out un sig ned porti on（部分）of headersegywritesuaddhead-put headers on bare traces and set the track and ns fields sustrip remove the SEGY headers from the traces supaste-paste existing（ 現(xiàn)存的）SE

5、GY headers on existing data segyhdrs make segyascii and innards（內(nèi) 部 ） headers for bhedtopar,setbhed-edit ing the bin ary header filesura nge-get max and min values for non-zero header en tries suchw-cha nge header word using one or two header word fields sugethw-get the header words in su data suedi

6、t-exam ine segy diskfiles and edit headers suxedit-exam ine segy diskfiles and edit headers2常規(guī)的數(shù)據(jù)轉(zhuǎn)換命令a2b con vert ascii floats to binary b2a-c on vert binary floats to ascii ftn strip-c on vert fortra n floats to c-systels floats recast-recast data type （con vert from one data type to ano ther）h2b c

7、on vert 8 bit hexadecimal floats to binarytransp tran spose an n1 by n2 eleme nt matrix二. SEGY與 SU的轉(zhuǎn)換SEGY文件格式由三部分組成，鏡象頭文件，十進制頭文件和實際的地震記錄，而SU格式的文件只含有其第三部分。命令segyread可以實現(xiàn)兩種格式的轉(zhuǎn)換，使用如下：在“ big-endian ”平臺上，Segyread tape二/dev/rmtO verbose=1 en dia n=1 >data.su或者更常用一點的Segyread tape= /dev/rmt0 verbose=1 e

8、ndian=1 | segyclean > data.su命令行中斜線部分是SEGY磁帶的位置（或者是磁盤文件的位置），其它應(yīng)用看自述文檔。三. 典型命令的使用如下命令行輸入，注意主目錄中文件的變化和終端中的屏幕輸出。1.supla ne > data.susuxwigb < data.su &segyhdrs < data.subhedtopar < binary outpar=b in ary.parsetbhedbfile=b inarypar=b in ary.parparameter二valueparamenter2二value segywrit

9、eb2a < data.b inary n 1=5 > data.asciia2b vdata.ascii n 1=5 > data.b inarytransp < data.b inary n 1=5 >data.tr nsp2. Su數(shù)據(jù)簡單操作supla ne >data.susustrip < data.su head二data.headers > data.b insuaddhead <data.b in n s=1024 > data.susupaste < data.b in n s=1024 head=data.

10、headers >data.susura nge < data.susupla ne | sura ngesugethw < data.su key二tracl,tracr.offset,dt, ns | moresupla ne|sugethw key=tracl,tracr,offset,dtns output=b inary >file.b inmore file.b insushw < data.su key=sx a=6400 csupla ne |sushw key=sx a=6400 c=-100 j=5 | sugethw key=sx | mor

11、esuplane | sushw key=offset a=200 b=200 j=5 | sugethw key=offset | moresupla ne| sushw key=dt,sx ,offset,a=2000,6400,200b=0,0,200c=0,-100,0j=0,5,5 | sugethw key=dt,sx,offset | moresuedit data.su第二節(jié)CWP中圖形打印顯示工具X-WINDOW下的圖形打印1浮點數(shù)據(jù)繪圖常用的命令有xcon tour x con tour plot of f(x1,x2) via vector plot callximage

12、-x imgae plot of a uni formly-sampled fun cti on f(x1,x2)xwigb-x wiggle-trace plot of f(x1,x2) via bitmapxgraph-x grapher graphs ni pairs of (x,y) coord in atesfun cti onxmovie -image one or more frames of a uniformly sampled f(x1,x2)相應(yīng)的，在SU平臺上有以下程序suxc on toursuximagesuxwigbsuxgraphsuxmoviesuxmax例子

13、：supla ne | suxc on tour title=” con tuour ” &suplane |suximgae title=”image”&suplane | suxwigb title= ” wigb ” &suplane |suxgraph title=”graph ”&suplane |suxmovie title=”movie”&suplane | suxmax tilte=力 cmax &supla ne | jun k1.susupla ne | suadd no ise sn=20 >>jun k1.su

14、supla ne | suadd no ise sn=15 >>jun k1.susupla ne | suadd no ise sn=10 >>jun k1.susupla ne | suadd no ise sn=5 >>jun k1.susupla ne | suadd no ise sn=3 >>jun k1.susupla ne | suadd no ise sn=2 >>jun k1.susupla ne | suadd no ise sn=1 >>jun k1.susuxmovie < junk1.su

15、 n2=32 title=” frame=%g' loop=1 &2. PS下的圖形打印psc on tourpsimagepswigbpsgraphpsmoviepscubepswigp在SU平臺上相應(yīng)的程序有：supsc on toursupsimagesupswigb supsgraphsupsmovie supscube supswigp例子:supla ne > jun k.susupsc on tour <jun k.su title二con tour> data1.eps &supsimage vjunk.su title= ” imag

16、e” label1= “ sec”label2= ” tracenumber” > data2.eps &supswigbsu title=bitmap wigb traces> data3.eps &supsgraphsu title=graph > data4.eps &supsmovie <jun k.su title=movie > data5.eps &supscubesu title=coue plot> data6.eps &supswigpsu title=wiggle trace> data7.

17、eps &運行以上程序之后，進入主目錄，在所生成的*.eps文件上點擊右鍵，打幵方式選擇ggv，查看圖像。第三節(jié)常見處理以下幾乎每部分都有CWF自帶的DEMO,參見$CWPROOT/path/src/demos目錄。對于一般的情況來說，DEMO的文件執(zhí)行具有一定的順序性。一.動校正這一部分有兩個命令，sunmo和suvelan。使用分別如下：SUNMO - NMO for an arbitrary velocity fun ction of time and CDP命令格式為sunmo <stdi n >stdout opti onal parameters可選參數(shù)：tnm

18、o=0vnm o=2000ani s1=0相應(yīng)于NMOh速度的NM（時間 相應(yīng)于NMOh時間的NM速度 產(chǎn)生四次節(jié)點的兩各向異性系數(shù)ani s2=0cdp=smute=1.5時距曲線中，相應(yīng)于 tnmo的時間由tnmo和vnmc定義的CDPsamples with NMO stretch exceedi ng smute are zeroedlmute=25sscale=1len gth (in samples) of li near ramp for stretch mute=1 to divide output samples by NMO stretch factorin vert=0=

19、1 to perform (approximate) in verse NMOixoffset=0do not con sider cross-l ine offset=1 read cross-l ine offset from trace headerupward=0=1 to scan upward to find first sample to kill注意：在處理常速度反射層時，vnmc取單一常數(shù)就可以了； 在處理多層變速度反射層時，tnmo和vnmo總是成對岀現(xiàn)，且數(shù)據(jù)為相對應(yīng)的數(shù)組 ,如” tnmo=1,2vnmo=1500,2000”。關(guān)于 NMO勺 DEMO 進入 $CWPR

20、OOT/path/src/demos/NMO 操作如下：1. 拷貝NMC下的所有文件到主目錄下2. 依次輸入 xmodel make data xdata xvclaity xnmo clean xall ;3. 依次輸入 psmodel make data psdata psvclaity psnmo clean psall。請注意：在源碼中可能有錯誤，執(zhí)行之中有些內(nèi)容無法實現(xiàn)。二.疊加有以下命令： sustack、sudivstack ，說明如下：SUSTACK stack adjace nt traces hav ing the same key header word sustack

21、<stdi n >stdout Opti onal parametersRequired parameters:noneOpti onal parameters:key=cdp header key word to stack onno rmpow=1.0 each sample is divided by theno rmpow'th n umber of non- zero values stacked (n ormpow=0 selects no divisio n)verbose=0 verbose = 1 echos in formati onSUDIVSTACK

22、 Diversity Stack ing using either average power or peak power withi n win dowsRequired parameters:NoneOpti onal parameters:key=tracf key header word to stack onwinlen=0.064 window len gth in sec on ds.typical choices: 0.064, 0.128, 0.256,0.512, 1.024, 2.048, 4.096if not specified the entire trace is

23、 usedpeak=1 peak power opti on default is average powerexamples :For duplicate field shot records:susort < field.data tracf | sudivstack > stack.dataFor CDP ordered data:sudivstack < cdp.data key=cdp > stack.data關(guān)于DEMOS進入$CWPROOT/path/src/demos/Stacking?Phase_Weighted_Stacking，輸入 supws文件

24、，觀察主目錄下的文件變更情況。三抽道集常用命令，susort，使用說明：SUSORT sort on any segy header keywordssusort <stdin >stdout +-key1 +-key2 .susort supports any number of (secondary) keys with either ascending(遞升)(+, the default)or desce nding (-) directi ons for each. The default sort key is cdp.Note: Only the follow ing

25、 types of in put/output are supportedDisk in put -> any outputPipe in put -> Disk outputNote: If the the CWP_TMPDIR en vir onmen t variable is set useits value for the path; else use tmpfile()Example:To sort traces by cdp gather and within each gather by offset with both sorts in ascendingorde

26、r:susort vINDATA >OUTDATA cdp offset關(guān)于 demos 進入 $CWPROOT/path/src/demos/sorting_trace/tutorial輸入Xsort，PSsort 文件即可。由于以上三部分密不可分，特以速度分析一部分為例，1、產(chǎn)生數(shù)據(jù)nx=100 fx=0 dx=80nz=110 fz=0 dz=50unif2 vmodel ninf=4 n x=$ nx n z=$ nz dx=$dx dz=$dz v00=5000.0,6000.0,8000.0,10000.0,15000.0 |ximage n1=$nz f1=$fz d1=$

27、dz n2=$nx f2=$fx d2=$dx windowtitle="Model" lege nd=1 un its="wavespeed" wbox=$WIDTH hbox=$HEIGHT xbox=$WIDTHOFF ybox=$HEIGHTOFF &2、產(chǎn)生數(shù)據(jù)REF1="0.0909091:-4.0,1.0;12.0,1.0"REF2="0.1428570:-4.0,2.2;12.0,2.2"REF3="0.1111110:-4.0,3.5;12.0,3.5"REF4=&qu

28、ot;0.2000000:-4.0,5.0;12.0,5.0"fpeak=25.0 # should be half ny quist to avoid all spatial alias ingdvdz=2.0 # velocity gradie nt (dv/dz)dvdx=0.0 # velocity gradie nt (dv/dx)v00=5.0# P-wave velocity at surface in kft/sob=0# to elimi nate the turned ray con tributi onn xo=64 fxo=0.1 dxo=0.1 # offs

29、et in formati on: n umber, first, spac ingnxs=12 fxs=1.4 dxs=-0.1 # shot information: number, first, spacingn t=501 dt=0.004# time in formati on: n umber, spac ingecho "Making synthetic data for demo"sus ynlv v00=$v00 fpeak=$fpeak ndpfz=10 dvdz=$dvdz ob=$ob dt=$dt n t=$ nt verbose=0 ref=$R

30、EF1 ref=$REF2 ref=$REF3 ref=$REF4 n xo=$ nxo fxo=$fxo dxo=$dxo n xs=$ nxs fxs=$fxs dxs=$dxs |suchw key1=cdp key2=gx key3=sx b=1 c=1 d=2 |suaddnoise sn=50 f1=4.0 f2=8.0 f3=20.0 f4=25.0 >modeldata2、動校正sunmo < modeldata cdp=1500,2000,2500,3000tnm o=0,0.34,0.625,0.875,1.13 vnm o=5000,6000,7050,841

31、0,10000tnmo=0,0.335,0.630,0.875,1.1 vnmo=5000,6000,7180,8350,9760 tnmo=0,0.35,0.64,0.88,1.1vnm o=5000,6000,7180,8380,9590tnmo=0,0.64,0.88,1.1 vnmo=5000,7200,8440,9740 > nmodata &3、NMOSsuw ind <nm odata key=sx s=1400 j=250 |suga in tpow=2 gpow=0.5 |suximage label1="Time" label2=&q

32、uot;Gather" title="Every 5th Shot Record After NMO" wi ndowtitle="NMO" lege nd=1 un its="amplitude" f2=1 d2=0.078125 f2n um=1 d2n um=5 wbox=$WIDTH hbox=$HEIGHT xbox=$WIDTHOFF3 ybox=$HEIGHTOFF &4、抽道集，疊加susort <nm odata |sustack no rmpow=1.0 >stackdata5、抽道集

33、，疊加繪圖suga in vstackdata tpow=2 gpow=0.5 |suximage label仁"Time" label2="CMP" title="Stack" windowtitle="Stack" f2=350 d2=50 legend=1 units="amplitude" wbox=$WIDTH hbox=$HEIGHT xbox=$WIDTHOFF4 ybox=$HEIGHTOFF &四. 反褶積常用命令sufxdecon，說明：SUFXDECONia ndo

34、m no ise atte nuation by FX-DECONvolutio nsufxdec on vstdi n >stdout Opti onal ParametersRequired Parameters:No neOpti onal Parameters:taper=.1 len gth of taperfmi n=6.mini mum freque ncy to process in Hz (accord to twle n)fmax=.6/(2*dt) maximum frequency to process in Hztwlen=entire trace time w

35、indow length (minimum 300ms for lower freqs)n trw=10n umber of traces in win down trf=4n umber of traces for filter (smaller tha n ntrw)verbose=0 =1 for diag no stic pr inttmpdir=if non-empty, use the value as a directory path prefixfor stor ing temporary files; else, if the CWP_TMPDIRen vir onment

36、variable is set, use its value for the path;else use tmpfile()關(guān)于DEMO的使用，如下：進入$CWPROOT/src/demos/wie ner levi nson,拷貝所有文件到主目錄下，在中斷中輸入make,依次輸入 XDecon1 PSDecon1 ； XDecon2 PSDecon2； XDecon3 PSDecon3； XDecon4 PSDecon4； Xshape PSshape。例1、1、產(chǎn)生數(shù)據(jù)l=$CWPROOT/i ncludeL=$CWPROOT/libmake./traces |suaddhead n s=

37、512 |sushw key=dt a=4000 |suaddno ise sn=200 |suconv filter=1152,-384,-904,288,174,-34,-12 >modeldatarm traces2、顯示模型suxwigb <modeldata title="Data: 64ms reverbs" wi ndowtitle="Data" label1="Time (sec)" label2="Trace" wbox=$WIDTH hbox=$HEIGHT xbox=$WIDTHO

38、FF1 ybox=$HEIGHTOFF1 &3、自相關(guān)suga in vmodeldata tpow=$tpow |suacor n t=31 |suxwigb title="Autocorrelation" wi ndowtitle="AutoCorr" label1="Time (sec)" label2="Trace" wbox=$WIDTH hbox=$HEIGHT xbox=$WIDTHOFF2 ybox=$HEIGHTOFF1 &4、脈沖化信號supef vmodeldata maxla

39、g=.04 |suxwigb label1="Time" label2="Trace" title="Spiking Decon: 4,40ms" wi ndowtitle="Spike" wbox=$WIDTH hbox=$HEIGHT xbox=$WIDTHOFF3 ybox=$HEIGHTOFF1 &5、脈沖化后的自相關(guān)supef vmodeldata maxlag=.04 |suga in tpow=$tpow |suacor n t=31 |suxwigb title="Autocor

40、after spike" windowtitle="AutoCorr/Spike" label1="Time (sec)" label2="Trace" wbox=$WIDTH hbox=$HEIGHT xbox=$WIDTHOFF1 ybox=$HEIGHTOFF2 &6、追蹤反射，反射注意反射層supef vmodeldata maxlag=.04 |supef minl ag=.05 maxlag=.16 |suxwigb label1="Time" label2="Trace&q

41、uot; title="PEF: 50,160ms (Note dippi ng reflector!)" wi ndowtitle="PEF" wbox=$WIDTH hbox=$HEIGHT xbox=$WIDTHOFF2 ybox=$HEIGHTOFF2 &7、帶通濾波supef vmodeldata maxlag=.04 |supef minl ag=.05 maxlag=.16 |sufilter f=5,15,80,100 |suxwigb label1="Time" label2="Trace"

42、; title="Spike, PEF, BandPass" wi ndowtitle="Fi nal" wbox=$WIDTH hbox=$HEIGHT xbox=$WIDTHOFF3 ybox=$HEIGHTOFF2 & 例2、1、數(shù)據(jù)sus ynlv nt=201 dt=0.004 ft=0.0 nxo=1 n xs=100 dxs=.025 fxs=0.0 er=0 ob=0 v00=2.0 dvdz=0 dvdx=0 fpeak=30 smooth=1 ref="l：-l.,.l；7.,.5" ref="1

43、:-1.,.5;7.,.2" ref="2:-1.,.5;7.,.9" |sushw key=d2 a=.O5 >sus yn l.outsufilter <sus yn l.out >susyn l.flt2、加噪聲suaddnoise < susyn1.out sn=8 f=4,8,100,125 amps=0,1,1,0 |sufilter >sus yn 1.s n=4.flt3、繪圖suxmovie <sus yn 1.flt label1="Time s" label2="Trace #

44、" d1n um=.1 d2n um=10 n1=201 n2=100 d1=.004 d2=1 f1=0 f2=1 clip=30. -geometry $WIDTHx$HEIGHT+$WIDTHOFF1+$HEIGHTOFF1 title="Sig nal" perc=99.5 &suxmovie <sus yn 1.s n=4.flt label1="Time s" label2="Trace #" d1n um=.1 d2n um=10 n1=201 n2=100 d1=.004 d2=1 f1=0 f

45、2=1 clip=30. -geometry $WIDTHx$HEIGHT+$WIDTHOFF1+$HEIGHTOFF2 title="Data" perc=99.5 &5、反褶積sufxdec on <sus yn 1.s n=4.flt >sus yn 1.s n=4.fx n trw=100suxmovie <sus yn 1.s n=4.fx label1="Time s" label2="Trace #" d1n um=.1 d2n um=10 n1=201 n2=100 d1=.004 d2=1

46、f1=0 f2=1 clip=30. -geometry $WIDTHx$HEIGHT+$WIDTHOFF2+$HEIGHTOFF1 title="Fxdcn over Data" perc=99.5 &label1="Time s" label2="Trace #" d1n um=.1 d2n um=10 n1=201 n2=100 d1=.004 d2=1 f1=0 f2=1 clip=30. -geometry $WIDTHx$HEIGHT+$WIDTHOFF2+$HEIGHTOFF2 title="Fxdcn

47、 over Sig nal" perc=99.5 &7、繪圖suxmovie n1=201 n2=100 d1=.004 d2=1 f1=0 f2=1 clip=30. label1="Time s" label2="Trace #" d1n um=.1 d2n um=10 -geometry $WIDTHx$HEIGHT+$WIDTHOFF3+$HEIGHTOFF1 title="Diff: sig nal - fx(sig nal)" perc=99.5 &suop2 sus yn 1.flt sus y

48、n 1.s n=4.fx op=diff |suxmovie label1="Time s" label2="Trace #" d1n um=.1 d2n um=10 n1=201 n2=100 d1=.004 d2=1 f1=0 f2=1 clip=30. -geometry $WIDTHx$HEIGHT+$WIDTHOFF3+$HEIGHTOFF2 title="Diff: sig nal - fx(data)" perc=99.5 &五. 帶通濾波常用命令為subfilt ，說明：SUBFILT- apply Butte

49、rworth ban dpass filter subfilt <stdin >stdout optional parameters Required parameters:if dt is not set in header, then dt is mandatoryOpti onal parameters: (ny quist calculated intern ally) zerophase=1=0 for mini mum phase filterlocut=1=0 for no low cut filterhicut=1fstoplo=0.10*( nyq)=0 for

50、no high cut filterfreq(Hz) in low cut stop bandastoplo=0.05 fpasslo=0.15*( nyq)upper bou nd on amp at fstoplo freq(Hz) in low cut pass bandapasslo=0.95 fpasshi=0.40*( nyq) apasshi=0.95lower bou nd on amp at fpasslo freq(Hz) in high cut pass bandlower bou nd on amp at fpasshifstophi=0.55*( nyq) astop

51、hi=0.05freq(Hz) in high cut stop band upper bou nd on amp at fstophiverbose=0dt = (from header)簡單的舉個例子，=1 for filter design infotime sampli ng in terval (sec)Supla ne > data.suSubfilt < data.su > dataoutSubxwigb < data.suSubxwigb < dataout 關(guān)于DEMOS勺使用，如下： 進入目錄，雙擊 xbfilt1 , xbfilt2.六.偏移

52、常用的命令為 sugazmig、sumigps、sumigpspi。使用說明如下：SUGAZMIG SU version of Jeno GAZDAG's phase-shift migratio n forzero-offset data .sugazmig <in file >outfile vfile= opti onal parametersOpti onal Parameters:dt=from header(dt) or .004 time sampli ng in tervaldx=from header(d2) or 1.0midpo int sampli

53、ng in tervalft=0.0first time samplen tau=nt(from data)n umber of migrated time samplesdtau=dt(from header) migrated time sampli ng in terval ftau=ftfirst migrated time sampletmig=0.0times corresp onding to in terval velocities in vmigvmig=1500.0in terval velocities corresp onding to times in tmigvfi

54、le= n ame of file containing velocities verbose=0 verbose = 1 echoes in formati ontmpdir= if non-empty, use the value as a directory pathprefix for storing temporary files; else if thethe CWP_TMPDIR en viro nmen t variable is set use its value for the path; else use tmpfile()SUMIGPS MIGratio n by Ph

55、ase Shift with tur ning rayssumigps <std in >stdout opti onal parmsRequired Parameters:No neOpti onal Parameters:dt=from header(dt) or .004 time sampli ng in tervaldx=from header(d2) or 1.0dista nee betwee n sucessive cdp'sffil=0,0,0.5/dt,0.5/dt trapezoidal window of frequeneies to migrate

56、 tmig=0.0times eorresp onding to in terval velocities in vmigvmig=1500.0in terval velocities eorresp onding to times in tmigvfile= binary (non-ascii) file containing velocities v(t)n xpad=0n umber of cdps to pad with zeros before FFTltaper=0len gth of li near taper for left and right edgesverbose=0=

57、1 for diag no stic pri nttmpdir=if non-empty, use the value as a directory pathprefix for storing temporary files; else if thethe CWP_TMPDIR en viro nmen t variable is set use its value for the path; else use tmpfile()SUMIGPSP- Gazdag's phase-shift plus in terpolation migrati on forzero-offset d

58、ata , which can han dle the lateralvelocity variati on.sumigpspi <in file >outfile vfile= opti onal parametersRequired Parameters:nz=n umber of depth sapmlesdz= depth sampli ng in tervalvfile= n ame of file containing velocities(Please see Notes below con cer ning the format of vfile)Opti onal Parameters:dt=from header(dt) or .004 time sampli ng in terval dx=from header(d2) or 1.0 midpo int sampli ng in terval tmpdir=if non-empty, use the value as a directory pathprefix for storing temporary