topic Re: Raster Calculator - applying the following formulae for MODIS NDVI in Data Management Questions

Raster Calculator - applying the following formulae for MODIS NDVI

JonathanMcCloskey — Mon, 24 May 2010 08:15:49 GMT

Hi,

I am trying use MODIS Surface Reflectance Bands 1 and 2 rasters to calculate my own daily NDVI products using the following formula

NDVI = (Raster 1 - Ratser 2)/(Raster 1 + Raster 2);

The pixel values should be in decimals but when I run through Raster Calculator I get whole numbers and everything is zero. Does anyone know off a way to get the results in decimals?

Many thanks

Jon

Re: Raster Calculator - applying the following formulae for MODIS NDVI

DanPatterson_Retired — Mon, 24 May 2010 09:38:11 GMT

did you copy and paste the equation from the raster calculator? the first subtraction says Ratser 2
also, did you type in the equation or did you select rasters and the operands to form the expression?

Re: Raster Calculator - applying the following formulae for MODIS NDVI

JonathanMcCloskey — Mon, 24 May 2010 09:46:29 GMT

Dan,

Nope the equation was just typed in and is short names for the actual layers, everything i sselected from the layers. The formulae works but I get the values in whole numbers ie -1, 0, 1 (this is the range of NDVI values) however I need to know the decimal figures to 2 decimals points. ie 0.23, 0.47.......... etc.

Raster calculator seems to automatically round the decimals to the nearest whole number which is casuing me the problem.

Many thanks

Jon

Re: Raster Calculator - applying the following formulae for MODIS NDVI

JonathanMcCloskey — Mon, 24 May 2010 11:31:15 GMT

sorted, just have to add float to the start of the equation

thanks

Re: Raster Calculator - applying the following formulae for MODIS NDVI

Khairul_AzwanMohamad — Wed, 01 Dec 2010 07:08:51 GMT

http://scienceray.com/earth-sciences/ndvi-a-vegetative-index/