There are many ways to express the direction, so similar as to be easily confused.
Especially the Prepositions (prep.), which makes the beginners be at a loss as to what to do exactly. In some cases, the difference lies in a single word, but a miss is as good as a mile. For this purpose, I collect some examples about directions, and here I want to share with you.

1. The difference between the use of “in the west” and “on the west”.

A．”in the west” shows the absolute direction in our life and geographic position.
Take the following sentence for example: The sun rises in the east and sets in the west.

B．”on the west” indicates one thing locates on the direction of another thing, the direction here means the relative direction. For example: Thailand is on the east of Laos.

2. in (to，on，at) the east of

A．To express “A” locates on the east of “B”, that is, if “A” is in the range of “B”, we say “A is in the east of “B”, for example:
Japan is in the east of Asia. Italy is in the south of Europe.

B．Suppose “A” locates on the east of “B”, if “A” is in the range of “B”, we say “A is in the east of “B”, for example:

A is outside the pale of B, and a certain distance apart, we use “A” lies to the east of “B”, sometimes there is an ellipsis of “to the” in that sentence.
e.g. France lies (to the) east of England.

C．On the understanding that “A” locates on the east of “B”, and if “A” adjoins “B”, the sentence “A is on the east of B” express it to the point. For example,
Guangdong is on the south of Hunan.

D．supposing that we see the position words as a single entity or one point, we can use “A” is at the east of “B” e.g. There was a big battle at the north of the Liaodong Peninsula.

E．If we want to give expression to “A locates on the east of B and they are l00km apart”, we can say “A lies l00km to the east of B”，as well as “A lies 100km east of B”. The latter is more common in the United States. e.g. The plane crashed 30 miles south of the city.

3. In China, we express the directions which are opposite to the “north, south, east, west”.

And thus we have the following expression differences between Chinese and English.

东南方：southeast 西南方：southwest

西北方：northwest 东北方：northeast

take these two sentences as examples:

The Ming Tombs are located about 50 km to the northwest of Beijing.

Tiajin is situated l20 km southeast of Beijing.

4. We usually use ” by ” to express the ” deviation “.

正东偏北： east by north

正南偏西： south by west

正北偏东： north by east

正南偏东： south by east

e.g. We are sailing in the direction of east by north.

The island lies south by east from here.

5. Some other words which are very common.

front left 左前 rear left 左后

front right 右前 rear right 右前