I wanna know how can I get the Zone Number for gpt processing

gpt Terrain-Correction -Ssource=wrkdir/test3.dim -t wrkdir/test4.dim -PmapProjection=“Auto:WGS84” -PsaveIncidenceAngleFromEllipsoid=true -PpixelSpacingInMeter=15.0 -PdemName=“GETASSE30”

Error: No code “AUTO:WGS84” from authority “AUTO” found for object of type “ProjectedCRS”.

I used to use SNAP desktop to process Sentinel-1 Data.
I’m now writing a batch processing tool.
The required zone number is for UTM Zone 49/ WGS 84.

does this answer your question? Map Projection "UTM / WGS84 (Automatic)" for Terrain Correction processing with gpt

if you always need UTM Zone 49, you can as well use EPSG:32649 https://epsg.io/32649

I cloned source code from GitHub and I find code snippet below:
public static final int PCS_WGS84_UTM_zone_49S = 32749;
but the Number you provided is 32649.

The code 32649 is for the northern hemisphere the code 32749 is for the southern hemisphere.

You can have a look into the Reprojection processor.

Under ‘Predefined CRS’ you can see the possibilites you can enter.