Can you post the contents of the ENVI header file for this?  I could create some dummy data to try and reproduce it.  I do think there are some issues when exporting to ERDAS .img format.

Thank you for your reply. I can of course tell you the contents of header file . ENVI description = {   ENVI File, Created [Sun Nov 30 17:24:31 2008] [Sun Nov 30 17:24:45 2008]} samples = 2970 lines   = 2116 bands   = 44 header offset = 0 file type = ENVI Standard data type = 2 interleave = bsq sensor type = Unknown byte order = 0 map info = {aea, 1.0000, 1.0000, 5444777.0000, 9081015.0000, 1.0000000000e+003, 1.0000000000e+003, WGS-84, units=Meters} projection info = {9, 6378137.0, 6356752.3, 36.000000, 105.000000, 5000000.0, 5000000.0, 25.000000, 47.000000, WGS-84, aea, units=Meters} wavelength units = Unknown If you will I can email the file I used to you. ^o^   now I process the problem in two steps , firstly I use ENVI_OUTPUT_EXTERNAL_FORMAT to transform the file format , then I use Visual C++ 6.0 with the support of GDAL software package to reset the projection parameters. after that the result is OK.        

So your projection information above shows the projection center to be 36N and 105E (not 0).  When I open my dummy dataset with this header information, this is what I show: proj: aea pixel: 1000m Datum: WGS-84 UL Geo: 114 21 8.75E, 77 31 50.52N UL Map: 5444777, 9081015 When I use File ->Save File As ->Erdas Imagine the output .img has the exact same map info.  I also opened it in ArcGIS 9.3 and it shows the same map information. I then used ENVI_OUTPUT_TO_EXTERNAL_FORMAT, /imagine and it shows the same map information as above when I open it in ENVI.  So I am not sure what is getting changed when you output your file with this map info.  Does it show something different in Erdas Imagine?

thank you for your reply I want to upload some picture but i don't know how. The mapinfo information of the output of ERDAS is ok ,is the same of what you said, while the projection information is unexpected, Projection Type : Albers  Conic Equal Area  OK Spheroid Name : WGS 84          OK Datum Name : WGS84              OK Latitude of 1st standard  parallel: 47  OK Latitude of 2st standard  parallel: 25 OK Longitude of central meridian : 0  105 expected Latitude of origin of projection : 0  36 expected False easting at central meridian: 110948.189448 5000000 expected False northing of origin: 87266.462600 5000000 expected ERDAS 9.1 provided by Leica