Editing SD card partition recovery

Create an image of /dev/sdb called sdb.img
 dd if=/dev/sdb of=sdb.img

Mount the dd disk image

Establish sector size. Establish where the partition starts
 fdisk -l sdb.img

Calculate the offset
 startsector*sectorsize
 63*512=32256

Mount the disk image
 losetup --offset 32256 /dev/loop0 sdb.img

Fix the partition in the disk image
Use the appropriate version of fsck and switches
 e.g.  fsck.reiserfs --fix-fixable /dev/loop0

Mount the partition in the disk image (optional)
 mount /dev/loop0 /mnt/image

Also possible as
  mount -oloop,offset=32256 sdb.img /mnt/image

Restore the disk image to a new physical drive (ensure it is unused and not mounted)
Unmount the partition, if mounted
 umount /mnt

Unmount the disk image
 losetup -d /dev/loop0

Restore the fsck'd disk image
 dd if=sdb.img of=/dev/sdb