Proxy Yield Map Tutorial

Sample farm

For this tutorial we are going to use a sample farm in the Province of Buenos Aires, Argentina.

The crop is sunflower, and the NDVI reference layer was generated from an image acquired on December 27th, 2011, while the harvest was done during the first week of March 2012 (thus, the NDVI was acquired more than 60 days prior to harvest).

The purpose of the exercise is to:

• simulate that we're on the date that the NDVI image was taken
• apply 3 different sets of parameters to generate the corresponding proxy yield maps
• the points yield map is provided as a reference of the actual yields

To Enter the farm:

1. go to www.geoagro.com, click on 'Farm Services Center' on the upper right.
2. Login with user: [email protected], password: demo
3. click on Farms shared with me
4. Select farm: Demo_ProxyYield
5. You should see the main screen of this farm:
   
   

Reference layers 

We are going to use as Reference layers:

• Normalized Differential Vegetation Index (NDVI), generated from a Rapideye image (5mt resolution), on Dec. 27th, 2011
• Yield points map, corresponding to harvest done on the first week of March, 2012.

To review these layers:

1. Click on the   Navigation button
2. In the references panel turn on the NDVI20111227 'layer, under the InfoGIS group
3. In the references panel turn on the YieldsP_Sunflower_Field_1 'layer, under the Yields group
   
   
   

By turning on/off both layers, we can see the similar growth/yield patterns from the NDVI and Yield Points map

NDVI - 5mt. resolution - 12/27/2011	Yield Points - 1st week of March/2012

Warning:

The Farm Service Center does not show layer's symbology in the current version, this feature will be added soon. To view a layer's symbology, you can download it to a desktop GIS as shown in the Section below

Output layers 

We are going to generate three examples of proxy yield maps based on the NDVI map. We are going to review 3 cases, with:

• Mean yield of 2.257 tons/ha, and minimum/maximum yields of +/- 20%,
• Same mean yield, +/-30%,
• Same mean yield, and minimum, maximum yields corresponding to the min./max. values from the actual yield points map.

In a real case, these values are provided by the farm manager based on past experiences, and current crop conditions. 

The adopted mean/min./max. yields for the three cases are shown in the following table:

Field 1	NDVI	Mean Yield +/- 20% [tn/ha]	Mean Yield +/- 30% [tn/ha]	With min/max actual yield values [tn/ha]
Min	0.2	1.80	1.575	0.56
Mean	0.537	2.257	2.257	2.257
Max	0.66	2.70	2.925	4.65

To generate the proxy yield maps, we are going to apply a linear interpolation function, matching NDVI values with the linear function, to obtain the proxy yield values. The following figure shows the linear functions, for the 3 cases, for Field 1

The reference symbology applied is this: 

The generated proxy yield maps are shown below

Mean Yield +/- 20% [tn/ha] (layer Proxy_Yield_20pc_1)	Mean Yield +/- 30%  (layer Proxy_Yield_30pc_1)	With min/max actual yield values  (layer Proxy_Yield_Real_Field_1)

Download sample data to a desktop GIS

You can load this sample dataset to a desktop GIS, including:

• Download to shapefile format (for ArcView, ArcGIS users)
• Download to .lay or .gis file format (for GeoAgro GIS users)

In order to download:

1. click on the farm's name in the path in the upper right 
   
2. click on the service that you want to download (e.g.: Yield map, NDVI)
3. click on the download button
4. select the format to which you want to download (.lay, .gis, .shp)