pssac是朱露培老師所寫的小程式，是一個特別設計跟gmt參數相同的程式，適合寫在GMT script裡直接繪出sac圖形的有用工具。一年多前嘗試想要編譯成功他，卻一直沒有成功。今年彷彿又聽到大家有使用pssac的需求，於是提筆寫信問朱教授。朱教授熱心的回應，使我終於成功編譯pssac。
首先，你的linux/unix主機必須有gcc任何的c編譯器。
第二，你需要先安裝好GMT；GMT的安裝請參考GMT簡易安裝筆記。新版的GMT已經到4.5.5，但是安裝form大致上是一樣的。
第三，請到朱教授的個人網站下載pssac的原始碼。如果你的GMT版本是4.5以上，還請多下載新的pssac.c取代原本tar裡的檔案。
假設我們安裝好的GMT路徑是/opt/GMT4.5.2，netcdf的路徑為/opt/netcdf-3.6.3:
tar xvf pssac.tar不過直接使用原本的Makefile編譯成功的機會恐怕很少。請修改Makefile成如下的樣子：
cd pssac; mv pssac.c pssac-old.c
wget -c http://www.eas.slu.edu/People/LZhu/downloads/pssac.c
- CC = gcc
- GMT_INC = -I /opt/GMT4.5.2/include -I /opt/netcdf-3.6.3/include
- GMT_LIBS = -L /opt/GMT4.5.2/lib -L /opt/netcdf-3.6.3/lib -lgmt -lgmtps -lpsl -lnetcdf -lm -s
- CFLAGS = -O2 ${GMT_INC}
- pssac: pssac.o sacio.o
- ${CC} -o $@ $@.o sacio.o ${GMT_LIBS} ${CFLAGS}
- clean:
- @rm -f pssac *.o
接著請執行make。如果你有確實的寫對GMT以及netcdf的函式庫位置以及headers的位置，你應該可以看到如下的輸出：
gcc -O2 -I /opt/GMT4.5.2/include -I /opt/netcdf-3.6.3/include -c -o pssac.o pssac.c然而當你想要試著執行他的時候卻出現錯誤訊息：
gcc -O2 -I /opt/GMT4.5.2/include -I /opt/netcdf-3.6.3/include -c -o sacio.o sacio.c
gcc -o pssac pssac.o sacio.o -L /opt/GMT4.5.2/lib -L /opt/netcdf-3.6.3/lib -lgmt -lgmtps -lpsl -lnetcdf -lm -s -O2 -I /opt/GMT4.5.2/include -I /opt/netcdf-3.6.3/include
./pssac: error while loading shared libraries: libnetcdf.so.4: cannot open shared object file: No such file or directory可知pssac執行時期需要libnetcdf.so.4這個函式，利用find指令可以發現這個檔案就在/etc/netcdf-3.6.3/lib裡。原來是系統並不認識他，趕快加進來吧(別忘了切到root身份)！
echo "/opt/netcdf-3.6.3/lib" > /etc/ld.so.conf.d/libnetcdf.conf此時再執行pssac試試看：
echo "/opt/GMT4.5.2/lib" > /etc/ld.so.conf.d/libgmt.conf
ldconfig
Usage: pssac standardGMToptions [SACfiles] [-C[t1/t2]] [-E(k|d|a|n|b)(t[n]|vel)] [-Gr/g/b/c] [-I] [-Msize[/alpha]] [-Q] [-r] [-Sshift] [-V]
pssac plots SAC traces. If no SAC file names is provided in the command line, it expects (sacfile,[x,[y [pen]]) from stdin.
-C only plot data between t1 and t2
-E option determines
(1) profile type:
a: azimuth profile
b: back-azimuth profiel
d: epicentral distance (in degs.) profile
k: epicentral distance (in km.) profile
n: traces are numbered from 1 to N in y-axis
(2) time alignment:
tn: align up with time mark tn in SAC head
default is the reference time. Others are
n= -5(b), -3(o), -2(a), 0-9 (t0-t9)
vel: use reduced velocity
-G paint amplitudes larger than c with color r/g/b
-I integrate the trace before plotting
-M multiple traces
size: each trace will normalized to size (in y-unit)
size/alpha: if alpha<0, use same scale for all traces
else plot absolute amplitude multiplied by size*r^alpha
where r is the distance range in km
-Q square the trace
-r remove the mean value in the trace
-S shift traces by shift seconds
-V plot traces vertically
確定可以執行後，把他放到/usr/local/bin裡，這樣所有使用者都可以使用這隻程式啦！
再次感謝朱老師的熱心幫忙！
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