[Gdal-dev] how to translate .asc files (Info ASCII Grid) to .dem files (USGS ASCII DEM)

[maestrini_andrea at virgilio.it]

Hello gdal-dev,
I'm very new to gdal so please cope with my ignorance.
I have two questions for you

1.  .dem files are same things SRTM files 
(used by Radio Mobile Radio Propagation tool)???

2. when I invoke the 
command:

./gdal_translate -of USGSDEM input.asc output.dem

I have 
this error:
Input file size is 6592, 5728
ERROR 1: DEM Default Setup: 
Importing source dataset projection failed

what it means?

Is the 
command right?
Can I translate a file .asc into a file .dem and How I 
can do it????

Thank you,
Andrea