モルワイデ図法

 投稿者:しばっち  投稿日:2015年11月19日(木)22時40分27秒
  モルワイデ図法で投影します

SET BITMAP SIZE 800,400
SET WINDOW -180,180,-PI/2,PI/2
OPEN #1:NAME "world_50m.txt" !'「world_10m.txt」「world_50m.txt」「world_110m.txt」のいずれか。パスを指定。
SET #1: ENDOFLINE CHR$(10)
DO
   INPUT #1,IF MISSING THEN EXIT DO:A$
   IF A$<>"" THEN
      LET Z=POS(A$," ")
      LET KEIDO=VAL(A$(1:Z))
      LET IDO=VAL(A$(Z+1:LEN(A$)))
      LET TH=0
      FOR J=1 TO 10
         LET TH=TH-(SIN(2*TH)+2*TH-PI*SIN(RAD(IDO)))/(2*COS(2*TH)+2) !'ニュートン法
      NEXT  J
      LET X=KEIDO*COS(TH)
      LET Y=PI/2*SIN(TH)
      PLOT LINES:X,Y;
   ELSE
      PLOT LINES
   END IF
LOOP
CLOSE #1
SET LINE STYLE 3
FOR KEIDO=-180 TO 180 STEP 30
   FOR IDO=-90 TO 90 STEP 15
      LET TH=0
      FOR J=1 TO 10
         LET TH=TH-(SIN(2*TH)+2*TH-PI*SIN(RAD(IDO)))/(2*COS(2*TH)+2)
      NEXT  J
      LET X=KEIDO*COS(TH)
      LET Y=PI/2*SIN(TH)
      PLOT LINES:X,Y;
   NEXT  IDO
   PLOT LINES
NEXT KEIDO
FOR IDO=-90 TO 90 STEP 15
   FOR KEIDO=-180 TO 180 STEP 30
      LET TH=0
      FOR J=1 TO 10
         LET TH=TH-(SIN(2*TH)+2*TH-PI*SIN(RAD(IDO)))/(2*COS(2*TH)+2)
      NEXT  J
      LET X=KEIDO*COS(TH)
      LET Y=PI/2*SIN(TH)
      PLOT LINES:X,Y;
   NEXT KEIDO
   PLOT LINES
NEXT  IDO
END
 

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