# Reverse calculation

 Definition / notice: The use of the terms initial and terminal speed relates to the position within the calculation and the calculation direction in this calculation dialog. If you start off with collision speed at the starting point of the coordinates in the scope of a reverse calculation, then in this case, the initial speed is identical to the impact speed. If you then calculate back over a certain braking distance, then the terminal speed reached is the same as the initial braking velocity in the interval looked at.

The driving and movement lines in the distance-time diagram are calculated in intervals and displayed graphically in the scope of a reverse calculation.

In the first movement section, 6 intervals are offered, this certainly being sufficient for a variety of calculations without impairing the clarity. In the case of more complex sequences of accidents events, you can freely define further calculation intervals by attaching further calculation intervals to the respective last calculated position and the current speed there.

The input in the respective interval concerned takes place row by row and from left to right, beginning in the top left hand corner of the calculation table. As soon as you have entered 3 of 5 values in the first input line, the missing values ware calculated and displayed. If you have made a typing error, your attention will be drawn to more or less meaningful suggestions.

This is how the calculation dialog looks for the reverse calculation:

You can switch between mph and ft/s at any time using this box - even whilst calculating.

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Enter three of the possible five values, the missing ones will be calculated. The input values are highlighted in white, calculated ones in gray. In the example above, a collision speed of 3 mph was entered whereby there was a deceleration prior to the collision over a distance of 60 ft with -26 ft/s². The speed at the beginning of the deceleration results in 38.2 mph.
Here you can label a calculated interval that will also be printed in the protocol later on.
The calculated path of the vehicle can be given a speed scale. which is set in this box. In addition to the time and position input, with this option, you also see the current speed at that position in the diagram.
This option enables you to set the direction of the vehicle or the object examined in relation to the starting point of the coordinates.
Here you can enter labels for the individual calculation intervals which, for example, describe the current driving maneuver. This data is adopted in the protocol and alleviates the allocation.
This function adopts the current calculation and the dialog is closed. In the distance-time diagram, the calculated path of the vehicle is now attached to the cursor and can be placed in the desired position (e.g. the starting point of the coordinates) by clicking the mouse.
This button enables you to open a PDF in which your current calculations incl. the calculation equations used are documented.

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Here, the distance-time or distance-speed course is displayed in relation to the current ststus of calculation.

Remember that you can edit the course of movement adopted in the diagram at any time: If you click on the course of the vehicle and have thus selected it, you can change the line type, line thickness, the color of the graph or the font and size under Select font and color. After a right-click, select 'Properties' from the context menu, which will open the original calculation dialog. You can now edit or correct your calculation, add comments, select or deselect the speed scale or change the direction of movement. You can also copy the graphs from the context menu, in order to, for example, work on them in a different calculation with different deceleration values without having to enter the entire interval again. Finally, the entire calculation  with the graph can be deleted via the menu item 'Delete'.

And this is how the example above looks in the drawing window: