Normally, to mount VMDK on Linux, you can follow these steps 

But what if the VMDK in question contains GPT with NTFS inside?  How do you find the offset and mount it?

#first losetup the raw disk
losetup /dev/loop0 ./file-flat.vmdk

#to find out offset do this
parted /dev/loop0
unit s
print
#find the start offset of the partition you're looking for and multiply by 512 (mine was 135266304 - yours will likely differ)

#use the offset to mount the actual partition
losetup -o 135266304 /dev/loop1 /dev/loop0

#now mount it
mount.ntfs-3g /dev/loop1 /mnt/vmdk