here's my best guess based on your post's info:

i'm explicitly aliasing the target table, so it might make it a little clearer:

UPDATE MyTarget

SET MyTarget.updtbl_lat = i.infotbl_lat,

MyTarget.updtbl_long = i.infotbl_long

FROM UPDTABLE MyTarget

INNER JOIN INFOTABLE i

ON MyTarget.updtbl_number = i.infotbl_number

INNER JOIN DTLTABLE d

ON d.dtltbl_group = i.infotbl_group

INNER JOIN DTLTABLE e

ON e.dtltbl_code = MyTarget.updtbl_code