View source for How are productivity maps generated?

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== Remote Sensing basics  ==

Please review the following articles, to get familiar with the basics on Remote Sensing for Agriculture. This is recommended to understand how Productivity Maps are generated 

*'''[http://www.extension.org/pages/Agricultural_Remote_Sensing_Basics Remote Sensing Basics]''' (extension.org) 
*'''[http://extension.missouri.edu/publications/DisplayPub.aspx?P=EQ453 Precision Agriculture: Remote Sensing and Ground Truthing]''' (University of Missoury Extension) 
*'''[[NDVI - Vegetation Index|Normalized Differential Vegetation Index (NDVI) Maps]]'''

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== Methodology - combining NDVI from past seasons  ==

Productivity maps are generated based on the combination of Vegetation Index maps, through geo-statistical analysis. It's&nbsp;is an automated and objective, that allows to compare the field production and variability in different times, in a single map. 

Remote sensing imagery is selected in key dates, when crops are vigorous, and Vegetation Index (NDVI) maps are generated on those dates. These layers are then normalized, and integrated in the productivity map.&nbsp; It's also possible to include information from previous yield monitor maps if available. 

The following sample images and corresponding NDVI illustrate this process: 

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{| cellspacing="1" cellpadding="1" border="1" width="200"
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| [[Image:MZ landsat 8mar04.jpg|thumb|center|200px|MZ landsat 8mar04.jpg]]Landsat Image - Jan. 25, 2006 
| [[Image:MZ NDVI 8mar04.jpg|thumb|center|200px|MZ NDVI 8mar04.jpg]]NDVI - Jan. 25, 2006
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| [[Image:MZ landsat 6jan05.jpg|thumb|center|200px|MZ landsat 6jan05.jpg]]Landsat Image - June 1, 2005<br> 
| [[Image:MZ NDVI 6jan05.jpg|thumb|center|200px|MZ NDVI 6jan05.jpg]]NDVI - June 1, 2005
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[[Image:MZ landsat 25jan06.jpg|thumb|center|200px|MZ landsat 25jan06.jpg]] 

Landsat Image - Aug. 3, 2004 

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[[Image:MZ NDVI 25jan06.jpg|thumb|center|200px|MZ NDVI 25jan06.jpg]] 

NDVI - Aug. 3, 2004 

|}

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These images are integrated by analyzing each pixel, defining homogeneous production areas, and obtaining the productivity map. [[Image:MZ management zone map.jpg|frame|left|500px|MZ management zone map.jpg]] 

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== When is the right time to select imagery?  ==

NDVI values are closely related to phenological vegetation patterns. The&nbsp;phenological pattern describes the functioning of vegetation and allows understanding<br>its geographic variations, while the NDVI determines vegetative activity. 

the following figures show the relationship between NDVI evolution and crop phenology, in different research experiences 

{| width="200" border="1" cellpadding="1" cellspacing="1"
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| [[Image:NDVI Phen1.jpg|400px|NDVI Phen1.jpg]] 
| [[Image:NDVI Phen2.jpg|400px|NDVI Phen2.jpg]]
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| Effect of nitrogen levels on NDVI (cotton) <ref>''Spectral response of nitrogen fertilization in cotton (Gossypium species)'' Ansari, Mahey, et. al.</ref> 
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//put figures 

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A second aspect to consider is that in the maturity stage, and depending on the type of crop, there is a close correlation between NDVI values and actual yields. Thus, images to produce Productivity Maps are selected during that stage, to show yield variability. 

A third aspect is that&nbsp; 

Thus, the right time &nbsp;to...&nbsp; 

The Crop History is very important to evaluate the history and variability of the fields, when processing and interpreting NDVI maps, Producitivity maps, or other layers derived from remote sensing processing. This information includes the following, for each of the last crop seasons: If there was any extraordinary event, such as hail, drought, floods, etc. The crop planted in each field, with planting and harvesting date. 

Why is crop history important to analyze NDVI and Variability? 

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== How often should Productivity Maps be updated?  ==

La definición de ambientes se inicia en una campaña determinada pero es un proceso que permite mejorar continuamente especialmente al finalizar la primer campaña con la obtención de mapas de rendimiento. A partir de ellos se puede obtenerse información valiosa para retroalimentar el mapa de ambientes original. 


== References ==
<references /> 

[[Category:Productivity_maps]]