Opened 3 years ago

## #678 new bug

# projected pixel size goes to zero in -x, +y and -y, +x quadrants in resolution calculation

Reported by: | Brian B. Maranville <brian.maranville@…> | Owned by: | srkline |
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Priority: | minor | Milestone: | |

Component: | SANS Reduction | Keywords: | |

Cc: | Blocking: | ||

Task: |

### Description

in get2DResolution function, line 324 of NCNR_User_Procedures/Reduction/SANS/NCNR_utils.ipf (version 7.94) the projected detector size is calculated as

// the detector pixel is square, so correct for phi proj_DDet = DDet*cos(phi) + DDet*sin(phi)

but this will have the desired behavior (proj_DDet=DDet along x and y, but bigger in between the axes) only where x,y are both positive or both negative. Where the sign of x and y differ, the sign of cos and sin in the expression will differ and you will get a subtraction where you I think always want an addition.

In particular, when x = -y you will get complete cancellation, and proj_DDet will be zero! (at an angle of 3*pi/4 and 7*pi/4)

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