Opened 6 years ago

Closed 5 years ago

## #3385 closed task (fixed)

# Typo in the i.vi man page

Reported by: | micha | Owned by: | |
---|---|---|---|

Priority: | normal | Milestone: | 7.2.3 |

Component: | Docs | Version: | 7.2.0 |

Keywords: | Vegetation Index | Cc: | |

CPU: | Unspecified | Platform: | All |

## Description

I think there's a small error in the equation for MSAVI2 in the man page for i.vi.
Here's what appears:
MSAVI2 = (1/2)*(2(NIR+1)-sqrt((2*NIR+1)^{2-8(NIR-red)))
}

Should be (incorrect parentheses):

MSAVI2 = (1/2)*(2*NIR+1-sqrt((2*NIR+1)^{2-8(NIR-red)))
}

Can anyone verify?

### Change History (7)

### comment:1 by , 6 years ago

### comment:2 by , 6 years ago

it might be a typo indeed. can you correct the source code and submit a revision?

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I see that the source for MSAVI2 in i.vi is consistant with the docs. The equation in the source is:

result=0.5*(2*(nirchan+1)-sqrt((2*nirchan+1)*(2*nirchan+1)-8*(nirchan-redchan)));

whereas in:

Qi, J., Chehbouni, A., Huete, A.R., Kerr, Y.H., Sorooshian, S., 1994. A Modified Soil Adjusted Vegetation Index. REMOTE SENS. ENVIRO 48, 119–126.

The MSAVI2 equation is slightly different. There it's 0.5*(2*nir + 1 - sqrt(...))

??