Calculate MSAVI2 in Raster Calculator

[HarmenHuigens]

I would like to calculate a Modified Soil-Adjusted Vegetation Index 2 on the basis of Landsat 8 OLI imagery, bands 5 (NIR) and 4 (RED), using the Raster Calculator. The formula should be:

I have tried to convert this using the following map algebra expression in the Raster Calculator:

MSAVI2 = (2 * "NIR layer" + 1 - SquareRoot((2 * "NIR layer" + 1) ^ 2  - 8 * ("NIR layer" - "RED layer"))) / 2

The returned values are between 0.5 and 58113.5. They should be between -1 and 1 though, so something is not right.

Any ideas about what is going wrong here?

Thanks!

[DanPatterson_Retired]

^ is a boolean xor

Raster Calculator—Help | ArcGIS for Desktop

use pow or ** (I think)

is SquareRoot chosen from the list of operators or did you type it in

[HarmenHuigens]

Thank you; ** is indeed the power operator.

SquareRoot is chosen from the operators list.

The result seems to be better although I still get values between -202.015 and 1.00195, with a mean of 0.12. The formula should give values only between -1 and 1.

[DanPatterson_Retired]

2 * "NIR layer" .....    - 8 * ("NIR layer" - "RED layer"))) / 2

make sure you make judicious use of floating point values

2.0 * "NIR layer" ......- 8.0 * ("NIR layer" - "RED layer"))) / 2.0

[HarmenHuigens]

Thanks; this also helps: Max value is now at 1.0

The minimum value, however, is still at 202.015.

[DanPatterson_Retired]

sorry... can you re-write the latest incarnation and check the reference formula...it wouldn't be the first time that I saw one of those wrong