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### 4. Ground to Grid Angle

To convert angle *B7-Jerry-A1* to grid, we need the arc-to-chord correction for lines *Jerry-A1* and *Jerry-B7*. We have the former, now must compute the latter. Line *Jerry-B7* is longer and oriented more east-west than *Jerry-A1* so the magnitude of its arc-to-chord correction should to be larger.

We've shown that both arc-to-chord equations give the same results so we'll use Equation H-10.

The correction forJerry-B7is larger thanJerry-A1's as expected.

At *Jerry* the correction to *A1* is negative (angle left) and to B7 positive (angle right). The angle and corrections are shown in Figure K-7.

Figure K-7 Angle Corrections |

The grid angle *B7'-Jerry-A1', β _{G} , *is:

The user must decide if combined bascksight and foresight arc-to-chord correction is significant.