Geotiff metadata export

Tim_prp

Hi, 
I am trying to export a tagged geotiff for New Zealand NZVD2009. I downloaded the ascii files and imported to Global Mapper, and I searched the forum found that using the script for TIFF_IMAGE_DESC can add the tags for geotif, but the file is not correct the the "Raster_type". I'm trying to make a raster file with lat/lon and elevation value in it, but by using the export script I can only get either raster with RGB or elevation with point. I think it has to be under the "Raster_type pixel is Area" rather than "Raster_type pixel is point". The problem here is I can't get the "export_elevation" with "Area", it will always be "Point".
Can anyone help for this?

I am using this script: 

EXPORT_ELEVATION FILENAME="C:\NewZealand\Geoid\test.tif" \

TYPE=GEOTIFF SAMPLING_METHOD="BILINEAR" PALETTE=OPTIMIZED BAND_SETUP="1" \ 

TIFF_IMAGE_DESC="VERT_DATUM[''New Zealand Vertical Datum 2009'',2005,AUTHORITY[''EPSG'',''1039'']]"

I am trying to export the attributes with sample format to floating and raster type as Area.

Thank you for any suggestions and help.

Cheers,
Tim