FUNCTION MAKE_GEOTIFF_TAG,pmap,plongi,plati,big=big

  
if not keyword_set(big) then begin
check=where(plongi gt 180.,ct)
if ct gt 0. then plongi(check)=plongi(check)-360.
endif



gtag={MODELPIXELSCALETAG:dblarr(3),MODELTIEPOINTTAG:reform(dblarr(6,1),6,1),GTMODELTYPEGEOKEY:1,GTRASTERTYPEGEOKEY:1,GTCITATIONGEOKEY:'',GEOGRAPHICTYPEGEOKEY:32767,GEOGCITATIONGEOKEY:'',GEOGGEODETICDATUMGEOKEY:32767,GEOGANGULARUNITSGEOKEY:9102,GEOGELLIPSOIDGEOKEY:32767,GEOGSEMIMAJORAXISGEOKEY:3396190.0,GEOGSEMIMINORAXISGEOKEY:3396190.0,GEOGPRIMEMERIDIANLONGGEOKEY:0.0,PROJECTEDCSTYPEGEOKEY:32767,PROJECTEDCSGEOKEY:32767,PROJCOORDTRANSGEOKEY:17,PROJLINEARUNITSGEOKEY:9001,PROJSTDPARALLEL1GEOKEY:0.0,PROJFALSEEASTINGGEOKEY:0.0,PROJFALSENORTHINGGEOKEY:0.0,PROJCENTERLONGGEOKEY:0.0,PROJCENTERLATGEOKEY:0.0,PROJECTIONGEOKEY:0.0}


s=size(pmap,/dimension)
size_x=s(0)
size_y=s(1)


if not keyword_set(big) then begin
lon1=min(plongi(where(plongi ne 0.)))
lon2=max(plongi(where(plongi ne 0.)))
lat1=min(plati(where(plati ne 0.)))
lat2=max(plati(where(plati ne 0.)))
endif

if keyword_set(big) then begin
lon1=min(plongi)
lon2=max(plongi)
lat1=min(plati)
lat2=max(plati)
endif
                                  

print,lon1,lon2,lat1,lat2

proj_type=map_proj_init(8,SPHERE_RADIUS=3396190.0,LIMIT=[lat1,lon1,lat2,lon2])  

; 8 or 117

if not keyword_set(big) then begin
lonlatuv1=map_proj_forward([plongi(size_x/2,size_y/2),plati(size_x/2,size_y/2)],map_structure=proj_type)
lonlatuv2=map_proj_forward([plongi(size_x/2+1,size_y/2),plati(size_x/2,size_y/2+1)],map_structure=proj_type)
endif

if keyword_set(big) then begin
lonlatuv1=map_proj_forward([plongi(size_x/2.),plati(size_y/2.)],map_structure=proj_type)
lonlatuv2=map_proj_forward([plongi(size_x/2.+1),plati(size_y/2.+1)],map_structure=proj_type)
endif

resx=(lonlatuv2-lonlatuv1)[0]
resy=(lonlatuv2-lonlatuv1)[1]

if not keyword_set(big) then begin
TieLon=plongi(size_x/2.,size_y/2.)
TieLat=plati(size_x/2.,size_y/2.)
endif

if keyword_set(big) then begin
TieLon=plongi(size_x/2.)
TieLat=plati(size_y/2.)
endif

   
TieLonLat=map_proj_forward([TieLon,TieLat],map_structure=proj_type)

gtag.modelpixelscaletag=[resx,resy,0.]

gtag.modeltiepointtag=reform(fltarr(6),6,1)
gtag.modeltiepointtag(0)=size_x/2.
gtag.modeltiepointtag(1)=size_y/2.


gtag.modeltiepointtag(3)=TieLonLat(0)+0.*resx
gtag.modeltiepointtag(4)=TieLonLat(1)+0.*resy


GEOGSEMIMAJORAXISGEOKEY=3396190.0
gtag.gtmodeltypegeokey=1
gtag.GTRASTERTYPEGEOKEY=1
gtag.GTCITATIONGEOKEY='PCS Name = Mars2000 Equidistant_Cylindrical clon0'
gtag.GEOGRAPHICTYPEGEOKEY=32767
gtag.GEOGCITATIONGEOKEY='GCS Name = GCS_Mars_2000|Datum = Mars_2000|Ellipsoid = Mars_2000_IAU_IAG|Primem = Reference_Meridian'
gtag.GEOGGEODETICDATUMGEOKEY=32767
gtag.GEOGANGULARUNITSGEOKEY=9102
gtag.GEOGELLIPSOIDGEOKEY=32767
gtag.GEOGSEMIMAJORAXISGEOKEY=GEOGSEMIMAJORAXISGEOKEY;3396190.0
gtag.GeogSemiMinorAxisGeoKey=GEOGSEMIMAJORAXISGEOKEY
gtag.GEOGPRIMEMERIDIANLONGGEOKEY=0.0000000
gtag.PROJECTEDCSTYPEGEOKEY=32767
gtag.PROJECTIONGEOKEY=32767
gtag.PROJCOORDTRANSGEOKEY=17
gtag.PROJLINEARUNITSGEOKEY=9001
gtag.PROJSTDPARALLEL1GEOKEY=0.0000000
gtag.PROJFALSEEASTINGGEOKEY=0.0000000
gtag.PROJFALSENORTHINGGEOKEY=0.0000000
gtag.PROJCENTERLONGGEOKEY=0.0000000
gtag.PROJCENTERLATGEOKEY=0.0000000

RETURN,GTAG


END