a02aeb236c
Former-commit-id:06a8b51d6d[formerly 64fa9254b946eae7e61bbc3f513b7c3696c4f54f] Former-commit-id:9f19e3f712
125 lines
3.7 KiB
C
125 lines
3.7 KiB
C
/*=========================================================================*/
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/* FILE PATH/NAME: STAGE3_SOURCE/hrap.c */
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/* */
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/* FUNCTIONS CONTAINED IN THIS FILE: HrapToLatLong */
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/* LatLongToHrap */
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/*=========================================================================*/
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/*~~~INCLUDE FILES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
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#include <stdio.h>
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#include <math.h>
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#include "stage3.h"
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/***************************************************************************/
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/* FILE PATH/NAME: STAGE3_SOURCE/hrap.c */
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/* FUNCTION NAME: HrapToLatLong */
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/* FUNCTION: convert from HRAP coordinates to latitude-longitude */
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/***************************************************************************
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Function type:
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HRAP structure
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Called by function:
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(callback) locate
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Functions called:
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none
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Local variables:
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tlat - float; standard latitude in radians
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earthr - float; earth's radius (km)
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xmesh - float; mesh length at 60 deg North
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raddeg - float; conversion from radians to degrees
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stlon - float; standard longitude
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ll - HRAP structure; latitude/longitude
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******************************************** BEGIN HrapToLatLong ***********/
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HRAP HrapToLatLongPproc(hrap)
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point hrap;
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{
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double x, y, rr, gi, ang;
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double tlat, earthr, xmesh, raddeg, stlon;
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HRAP ll;
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earthr=6371.2;
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stlon=105.;
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raddeg=57.29577951;
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xmesh=4.7625;
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tlat=60./raddeg;
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x = (double)hrap.x - 401.;
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y = (double)hrap.y - 1601.;
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rr = x*x + y*y;
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gi = ((earthr * (1+sin(tlat)))/xmesh);
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gi=gi*gi;
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ll.y = asin((gi-rr)/(gi+rr))*raddeg;
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ang = atan2(y,x)*raddeg;
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if (ang < 0) ang=ang+360.;
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ll.x = 270+stlon-ang;
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if (ll.x < 0) ll.x=ll.x+360;
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if (ll.x > 360) ll.x=ll.x-360;
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return ll;
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}
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/********************************************* END HrapToLatLong ***********/
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/***************************************************************************/
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/* FILE PATH/NAME: STAGE3_SOURCE/hrap.c */
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/* FUNCTION NAME: LatLongToHrap */
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/* FUNCTION: convert latitude-longitude coordinates to DV point */
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/* structure at appropriate screen position */
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/***************************************************************************
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Function type:
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HRAP structure
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Called by function:
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Functions called:
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none
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Local variables:
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lat - float; latitude
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lon - float; longitude
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degrad - float; conversion degrees to radians
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earthrad - float; radius of earth
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stdlat - float; standard latitude
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stdlon - float; standard longitude
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mesh_len - float; grid mesh length at standard latitude
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tlat - float; standard latitude in radians
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latrad - float; point latitude in radians
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lonrad - float; point longitude in radians
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hrap - HRAP structure; hrap coordinate
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******************************************** BEGIN LatLongToHrap ***********/
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HRAP LatLongToHrapPproc(lat, lon)
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float lat, lon;
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{
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double degrad = 0.017453293;
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double earthrad = 6371.2;
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double stdlat = 60.;
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double stdlon = 105.;
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double mesh_len = 4.7625;
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double tlat, re, latrad, lonrad, r, x, y;
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HRAP hrap;
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tlat = stdlat*degrad;
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re = (earthrad*(1. + sin(tlat)))/mesh_len;
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latrad = lat * degrad;
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lonrad = (lon + 180. - stdlon) * degrad;
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r = re * cos(latrad) / (1. + sin(latrad));
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x = r * sin(lonrad);
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y = r * cos(lonrad);
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hrap.x = x + 401;
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hrap.y = y + 1601;
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return hrap;
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}
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/********************************************* END LatLongToHrap ***********/
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