According to the wiki, this is what the symbols mean:
The map is an overview of the playing field from the top down. If there is a building with a yellow roof it would show up as a yellow shape on the map, and thus might give away your position. Choose your colors wisely.
The map has several icons:
The teal circle with the line through it represents the player. The line points in the direction they are currently facing. Remember that the map is 3D so if you are looking up or down, the line in the circle will be pointing up or down and might make yourself harder to spot on the map.
A square represents the intel. The intel is coloured to represent which team it belongs to
A "plus" represents the HQ. It too is coloured to represent the team it belongs to
A white triangle above or below the Intel or base represents that the intel or base is ABOVE or BELOW the player in height.
A circle represents your team mates. They are always white. When your team captures the intel, red circles appear on the map for 1 minute. These represent enemies.