What is used to indicate the angular relationship of true north in land navigation?

The correct answer is the declination diagram. In land navigation, the declination diagram presents crucial information about the angular relationship between true north and magnetic north. It is typically found on maps and helps navigators understand the difference in degrees between true north, which is the direction along the earth's surface towards the geographic North Pole, and magnetic north, which is where a magnetic compass points.

By using the declination diagram, navigators can perform accurate conversions between true bearing and magnetic bearing, ensuring that their navigation techniques are reliable. This is particularly important in areas where the magnetic declination (the angle between true north and magnetic north) varies significantly due to geographic location.

Other options might relate to navigation but do not serve the specific purpose of indicating the angular relationship of true north. Azimuth charts can provide bearings but lack the clarity of a declination diagram regarding the relationship with true north. Topographic maps depict terrain features and elevations rather than specific navigational angles. Orientation tools assist in the navigation process but do not inherently convey the angle between true north and magnetic north. Therefore, the declination diagram is the optimal choice for this purpose.