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14 ARSPC, Land Cover Mapping Session
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Harmonic analysis of time-series MODIS vegetation index data for monitoring winter
crops in the Wimmera-Mallee region of
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
crops in the Wimmera-Mallee region of Victoria
Medhavy Thankappan1, Kenton Lawson2, Shanti Reddy1 and Phil Kokic2
1Geoscience Australia2Australian Bureau of Agricultural and Resource Economics
Acknowledgments
Geoscience Australia
Lan-Wei Wang
Bill Levett
Anis Islam
Alan Forghani
APSRU DPIF-QLD
Andries Potgieter
NLR Netherlands
Wout Verhoef
Albert van der Kamp
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
Alan Forghani
ABARE
Chun Liang
Milly Lubulwa
Albert van der Kamp
Agricultural Statistics
• Crop type, area & production: Ag Census and Survey (ABS), Farm surveys (ABARE)
• NAMS, SPREAD II: regional ag. land use mapping with satellite derived information and ABS statistics (BRS)
• Pastures from Space (CSIRO, WA Agric,
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
• Pastures from Space (CSIRO, WA Agric, Landgate)
• RCFS: shire-wise yield model for wheat and sorghum (QDPI&F)
• GAP: near-real-time crop-specific area and pre-harvest or in-season production estimates not available
Method
Study Area• Mallee and Wimmera Statistical Divisions comprising 16 SLAs in north western Victoria
• Predominantly agricultural, cereal crops, legumes and oilseeds
RS / Ancillary Data
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
RS / Ancillary Data• 16-day composite MODIS EVI at 250 m (2000 – 2006)• Land-use and very limited ground truth
Approach• HANTS-Harmonic ANalysis of Time Series (each crop year)• Non-agricultural pixels (water bodies / forests) masked• Unsupervised classification of HANTS outputs (ISOCLASS)• Aggregation of crop class area at SD and SLA levels
Study Area (Mallee & Wimmera SDs)
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
Harmonic Analysis
• Decomposes periodic phenomena into a series of functions (terms)
• Each term is defined by a unique amplitude / phase value
• Identification of land cover types is possible using values of
Amplitude
Phase
002π2π
Seasonal VI series
Time
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
is possible using values of phase, amplitude & additive term
Am
plitu
de
Re
sc
ale
d V
I
0 + 1
0 + 1 + 2
0 + 1 + 2 + 3
Adding successive terms to produce final curves
Decomposition of VI series into component terms
Why Harmonic Analysis?
• Vegetation exhibits distinctive seasonal patterns of variation with periodic characteristics
• Potential for significant data reduction (time-series)
• Not biased by data set (size, range or
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
• Not biased by data set (size, range or dominance of spectral features
• Acts as a noise filter for non-periodic influences introduced by processing or cloud
• Has been applied successfully to land-use / land cover studies including crops
HANTS Outputs A1A1
A2A2 P2P2
P1P1
A0A0
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
P3P3A3A3
Raw versus HANTS VI Profiles
0
1000
2000
3000
4000
5000
6000
7000
1 3 5 7 9 11 13 15 17 19 21 23
EV
I
Wheat
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
1 3 5 7 9 11 13 15 17 19 21 23
16-day period
0
500
1000
1500
2000
2500
3000
3500
4000
4500
1 3 5 7 9 11 13 15 17 19 21 23
16-day period
EVI
Original
HANTS
Field Peas
HANTS Partial Variance 2004
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
Am
plitu
de
1st term 2nd term 3rd term
HANTS Partial Variance 2004
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
Am
plitu
de
1st term 2nd term 3rd term
Clustering HANTS outputs
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
Results : Statistical Divisions (2000 - 2005)Mallee Statistical Division
0
200
400
600
800
1000
1200
1400
1600
2000 2001 2002 2003 2004 2005
Win
ter
Cro
p A
rea (
'000 h
a)
Wimmera Statistical Division
0
200
400
600
800
1000
1200
1400
1600
2000 2001 2002 2003 2004 2005
Win
ter
Cro
p A
rea (
'000 h
a)
MODIS-HANTS
ABS (crops)
ABS (+ pasture)
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
Crop Year Crop Year
Relative deviations are generally higher in Mallee for all years
The largest RD for Mallee (22.9%) and Wimmera (16.7%) was observed in 2000 (smaller time series?)
0
50
100
150
200
250
300
350
400
SLA
Win
ter
Cro
p A
rea (
'000 h
a)
ABS Ag Census
MODIS-HANTS
400
450
500
Win
ter
Cro
p A
rea (
'000 h
a)
2000
Results : SLAs (2000 & 2005) • Relative deviations for SLAs are higher (than SD) for both 2000 and 2005
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
0
50
100
150
200
250
300
350
400
Bu
loke N
ort
h
Bu
loke S
ou
th
Gan
naw
arr
a
Hin
dm
ars
h
Ho
rsh
am
Bal
Ho
rsh
am
Cen
tral
Mild
ura
Pta
Mild
ura
Ptb
NG
ram
pia
ns S
tArn
au
d
NG
ram
pia
ns S
taw
ell
Sw
an
hill B
al
Sw
an
hill C
en
tral
Sw
an
hill R
ob
invale
West
Wim
mera
Yarr
iam
bia
ck N
ort
h
Yarr
iam
bia
ck S
ou
th
SLA
Win
ter
Cro
p A
rea (
'000 h
a)
2005
• MODIS HANTS crop area estimates higher than ABS for most SLAs
SD25 (Wimmera)1,346,793 ha 1,187,276 ha 13.4
SD30 (Mallee)1,260,091 ha 11.9
7.8
1,125,256 ha
1,168,633 ha*
Summary Results Winter Crop Area 2000
ABS Ag Census 2001 RD (%)
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
1,346,793 ha 1,187,276 ha
1,238,317 ha*13.48.7
SD30 + SD252,606,884 ha 12.7
8.3
*Crops for pasture and hay included
2,312,532 ha
2,406,950 ha*
SD25 (Wimmera)1,222,260 ha 1,125,041 ha 8.6
SD30 (Mallee)1,312,896 ha 7.6
3.7
1,220,517 ha1,265,171 ha*
Summary Results Winter Crop Area 2005
ABS Ag Census 2006 RD (%)
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
1,222,260 ha 1,125,041 ha1,201,299 ha*
8.61.7
8.12.8
2,345,558 ha2,466,470 ha*
SD30 + SD252,535,156 ha
*Crops for pasture and hay included
Summary of Key Findings
• Winter crop area results for Mallee and Wimmera SDs comparable to ABS estimates, potential of HA for time series applications involving crop monitoring
• Significant reduction of time-series data volumes
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
• Significant reduction of time-series data volumes and noise, better classification results using EVI compared to NDVI
• Application areas that could benefit from HA include land-use / land-cover mapping
Thank you Questions ?
14th Australasian Remote Sensing & Photogrammetry Conference, Darwin 29 Sep – 3 Oct 2008
Questions ?
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