Time Traveler

I run to the South along the bank of the river, but it quickly turns to the Southeast. The forest is thick here. I find a place to hide and gather my wits. After a moment I decipher the message. PHULGLDQXV deciphers as MERIDIANUS. That means noon, or to the south, since the sun is always to the south at noon. That means Caesar's army must be either farther Southeast or due East of my location.