MODIS-based Cropland Classification in North America Teki Sankey and Richard Massey Northern Arizona University

Outline Datasets chosen for processing: 2000 and 2007 Preprocessing Classification Spatial and temporal extrapolation Crop type labeling

Preprocessing workflow MODIS data Re-projection Mosaicking Layer stacking NDVIBand 1 (RED)Band 2 (NIR) Min-value 16-day Composite Max-value 16-day Composite Cloud Filtering/smoothing 47 tiles, 8-day composites (Feb 2000 to Feb 2001) (Feb 2007 to Feb 2008)

Composites Cloud-covered pixels make up for most of the noise in the data stack 16-day minimum value composites for band 1 and band 2 as cloud reflectance is higher 16-day maximum value composite for NDVI as cloud NDVI is lower NDVI maximum value composite is more useful in classification

Cloud filtering NDVI Days NDVI Days Return Value Difference Direction Return Value Difference Direction NDVI Days NDVI Days Thresholds:- Return Value < 0.20 Difference > 0.15

Cloud filtering NDVI Days NDVI Days Difference NDVI Days NDVI Days Thresholds:- Difference > 0.15

Cluster computing workflow The NAU computing cluster has 32 cores each with 500 nodes, shared memory of 1.5 TB per node ENVI services engine and ENVI version 5.1 Master C Program Batch file for execution IDL code for each process Batch file for IDL process Node Allocation IDL parallel process

NDVI stack

Year 2007 No existing crop type map for classification needs labeling 2007 = 2000 in region-wise annual precipitation NASS CDL available for year 2007 Assumption: Similar spectral signatures between the two years

Region-wise annual precipitation statistics US ( , National Climatic Data Center)

NASS CDL availability for conterminous US

Spatial and Temporal Extrapolation USA  North America 2007  2000

Spatial extrapolation: GCE v1.0 Most accurate irrigated class = AOI-1 (4/4 maps) ( 63,102,129 acres) Further split: Agro-Ecological Zones

Agro-Ecological Zones based on length of growing period (GAEZ-FAO)

GCE v1.0 AOI-1 and Agro-Ecological zones

MODIS-based US Irrigation map, 2001 (Ozdogan and Gutman, 2008)

GCE v1.0 AOI-1, Agro-Ecological Zones, and Irrigated map

Irrigated map 2001 (US) GCE v1.0 Class1GCE v1.0 Class3 AEZ 1AEZ 2 AEZ 3 AEZ 14 AEZ 1AEZ 2AEZ 3 AEZ 14 ISODATA Classification Overlay …… Irrigated map 2001 (US) GCE v1.0 AOI-1GCE v1.0 AOI-3 AEZ 1AEZ 2 AEZ 3 AEZ 14 AEZ 1AEZ 2AEZ 3 AEZ 14 Class 1Class 2 Class 25 Class 1Class 2 Class 25 Group 1 Group 2 Group 3 Group 4Group 5 Group 6 Group 100 ISODATA Classification Class Grouping Overlay ……….. …… …… Spatial extrapolation: Spatial subsets

Spatial extrapolation

Spatial extrapolation: Labels Spectral correlation matrix Classes are grouped together (R 2 > 0.98)

Temporal extrapolation: 2007  AOI + Irrigated map + Agro Eco zone2007 NASS CDL 2007 AOI + Agro Eco zone Labeling of classes using NASS CDL 2007

Master-file Primary layers – Cropland extent – Crop type – Crop intensity – Irrigated/Rainfed Secondary layers – Temperature – Precipitation – Elevation AttributeNameValue Cropland ExtentNon-Cropland0 Cropland1 Irrigated/RainfedRainfed0 Irrigated1 Crop TypeNon-Cropland0 Wheat1 Rice2 Corn3 Barley4 Soybean5 Pulses6 Potatoes7 Cotton8 Others9 IntensityNo crop0 Single crop1 Double crop2 Double+ crop3 TemperatureCelsius-value- PrecipitationCentimeters-value- Elevationmeters-value- NASS CDL 2007 MIrAD US 2007 NCEP NARR 2007 SRTM DEM

Spectral database Isodata classification for each AOI Class comparison with master-file Group classes based on attributes Group member classes lie in ± 0.1 buffer of the group mean spectra for more than 80% of bands Spectral database for each attribute combination Corn: Irrigated, Single crop Wheat: Irrigated, Single crop Soybean: Irrigated, Single crop

Spectral database AttributeNameValue Cropland ExtentNon-Cropland0 Cropland1 Irrigated/RainfedIrrigated0 Rainfed1 Crop TypeNon-Cropland0 Wheat1 Rice2 Corn3 Barley4 Soybean5 Pulses6 Potatoes7 Cotton8 Others9 IntensitySingle crop0 Double crop1 Triple crop2 Triple+ crop3 TemperatureCelsius-value- PrecipitationCentimeters-value- Elevationmeters-value- Class IDBand 1Band 2………Band N Class ………0.60 Class ……… ……… ……… ……… ………0.61 Class M ………0.63 Cropland attributes Grouped classes for one set of attributes

Extrapolation rules: Correlation Spectral match between classes in 2007 and 2000 ISOdata classification 2007 result ISOdata classification 2000 result

Extrapolation rules: Buffer If the input spectra lies within ± 0.1 buffer of the database spectra for more than 80% of bands it is assigned the same label If secondary parameters indicate Drought or Abundance, buffer is adjusted accordingly Overall validation threshold: 90% Buffer

Extrapolation Generation of NDVI stack for non-US region Spatial extrapolation of labels to non-US region using updated spectral database Input spectra is assigned the same label if lies within ± 0.1 buffer of the database spectra for more than 80% of bands it Verification of extent using GCE v1.0 and secondary parameters

Class Labels Irrigated map 2000 (US) GCE v1.0 Class1GCE v1.0 Class3 AEZ 1AEZ 2 AEZ 3 AEZ 14 AEZ 1AEZ 2AEZ 3 AEZ 14 Class 1Class 2 Class 25 Class 1Class 2 Class 25 ISODATA Classification Class Grouping and Labeling: 2007 Overlay Label 1 Label 2 Label 3 Label 4Label 5 Label 6 Label 100 Temporal Extrapolation: 2007  2000 ……….. …… …… Cropland map 2000 (US) Cropland map 2007 Cropland map 2000 (North America) Spatial Extrapolation: US  non-US

Thank you!

Class labeling 2007 classes are labeled by geolocating at least 10 random points within the 2007 CDL class Classes between 2000 and 2007 are matched together via correlation (R 2 >0.98) Labeled as crop type ‘A’

Spatial and temporal extrapolation US classesNA_class1NA_class2NA_class3NA_class4NA_class5NA_class6NA_class7NA_class8NA_class9NA_class10NA_class11NA_class12NA_class13NA_class14NA_class15NA_class16NA_class17NA_class Spectral correlation matrix

Validation Preprocessing of MODIS data for validation year (2009) Generation of NDVI stack Generation of validation-file using spectral database Validation-file has same structure as master-file of normal year (2008) Comparison of NASS CDL for 2009 with the validation file