# Volume Difference of an Area Surveyed over different Time Periods

Pix4Dmapper can be used to calculate the volume difference of an area surveyed at two moments in time. The images of each flight need to be processed in a separate project, in which the volume of the area at this moment in time is computed. Then, the results of these computations can be used to calculate the difference of volume of an area.

The following table describes different examples of Cut and Fill volumes. These are computed using Pix4Dmapper for a mining area that has been surveyed with two flights (flight1: before excavation / deposit, flight2: after excavation / deposit).

Legend
Black line: The stockpile volume that is drawn in the Volumes view.
Before: The project made using the first flight.
After: The project made using the second flight.
Cut: The Cut volume as calculated by Pix4Dmapper (positive value).
Fill: The Fill volume as calculated by Pix4Dmapper (negative value).
Total: The Total volume given by Pix4Dmapper. It is computed by adding Cut and Fill volumes (Total = Cut + Fill).

 Figure 1. Total Volume as calculates by Pix4Dmapper.

Case A: cut volume only, extracted material Case B: cut volume only, added material

Cut Before                                      Cut After

Cut volumes have positive value.

Cut Before                                      Cut After

Cut volumes have positive value.

Volume Difference = Cut After - Cut Before.

Volume Difference has negative value: material was extracted.

Volume Difference = Cut After - Cut Before.

Volume Difference has positive value: material was added.

Case C: fill volume only, extracted material Case D: fill volume only, added material

Fill Before                                       Fill After

Fill volumes have negative value.

Fill Before                                        Fill After

Fill volumes have negative value.

Volume Difference = Fill After - Fill Before.

Volume Difference has negative value: material was extracted.

Volume Difference = Fill After - Fill Before.

Volume Difference has positive value: material was added.

Case E: cut and fill volume

Cut and Fill Before                                                                    Cut and Fill After

Cut volumes have positive value, Fill volumes have negative value.

Volume Difference = (Cut After - Cut Before) + (Fill After - Fill Before) =  (Cut After + Fill After) - (Cut Before + Fill Before) = Total After - Total Before

Volume Difference has negative value: material was extracted.

Volume Difference has positive value: material was added.