as above
topo data is normally in 16 bit SIGNED LSB format with sealevel set to ZERO
-- but some is in 16 bit signed MSB !!! ( older apple ppc cpu's )
all intel X86 CPU's are LSB!!!!
so a 16 bit signed image has pixel values from -32767 to +32768
and a UNsigned image has values from 0 to +65536
a lot of image editors can find the min/max , for 16 bit data i like Nip2 ( been using it for almost 10 years so...)
it has built in MATH functions
find the min
then subtract the negative value
this moves the min. to 0
to normalize it
you then find the new MAX
divide by that value and then multiply that image by 65536
or use a comandline tool like Gmic
to normalize it and convert it to UNSIGNED
Code:
gmic inputSIGNED.tiff -n 0,65536 -o outputUNsigned.tiff,ushort