How to combine a set of adjacent raster maps

HELP !!!!!!!

     Our Lab. is trying to use GRASS4.1 to implement some researches.

The primary job is to append the CHINESE process functin into the GRASS.

We have completed two programs about this job :

  (1) CXDRIVER : we modify XDRIVER and support some
            Chinese Hersh Fonts (Chinese vector fonts).

  (2) Chterm : is a xterm with Chinese input and output function.

     Now we will try to do some samples such as the "Spearfish Sample

Database" supported by USACERL. But we have a problem :

     We have a set of low altitude aerial photographs, which are translated

to raster map files by scanner and "r.in.tiff" (a command).

     How can I combine (or say match) a set of adjacent photographs (raster

map) in GRASS ??? (Is there some existent GRASS tools or functions can do

this work ? of course, this work must include some rectification jobs.)

as follows :

  +-------+ +-------+ +-------+-------+
  | | | | | | |
        | 1 | + | 2 | | 1 | 2 |
        | | | | | | |
  +-------+ +-------+ = +-------+-------+
              | | |
      + + | 3 | 4 |
              | | |
  +-------+ +-------+ +-------+-------+
  | | | |
  | 3 | + | 4 |
  | | | |
  +-------+ +-------+

     Thanks a lot !!!

     My e-mail address : jay@flower.amath.nchu.edu.tw
     1995/1/19 jay in TAIWAN