1. EOFI Service Trial 1: UN-IFAD – Crop Acreage
ESA request D2.3 (19 Oct) to clarify discrepancies between EOFI results and IFAD statistics
Explain discrepancy in the absolute area covered by irrigated crops (rice & irrigated crops classes) compared to IFAD figures
Specifically provide reasoning for the different level of observed irrigated crops area in 1996
Response by GeoVille on 29 Oct
Today’s telco important to...
Improve mutual understanding in interpreting IFAD’s area statistics
Put benefits & limitations of satellite based monitoring in context

2. EOFI Service Trial 1: UN-IFAD – Crop Acreage
Benefits of satellite-based monitoring
Synoptic views over large areas
Time series with flexible time intervals
Uniform scale and content
Guaranteed quality levels
Low cost compared to terrestrial measurements
1996
2000
2007
2010

3. EOFI Service Trial 1: UN-IFAD – Crop Acreage
1996 irrigated area
IFAD: 1,061 ha irrigated land in IFAD statistics
UNOPS mission report 2001: 3,200 ha of irrigated rice fields in 1996
EOFI: 6,230 ha rice + 2,713 irrigated crops from EOFI)
EOFI Service Trial 1: UN-IFAD – Crop Acreage
Can we compare the area figures?
What are possible reasons for the “delta”?
Methods of data collection (terrestrial sampling vs. blanket satellite coverage)
Reference area
Definition of features
Accuracy / error margins of land cover maps
Others?
IFAD
EOFI
1,061 ha  5,230 ha ha
8,943 ha  11,612 ha ha
Sources:
Joint verification of area figures required

4. EOFI Service Trial 1: UN-IFAD – Crop Acreage
#1: Are the figures representative for the same area?
EOFI covers entire PHBM project area (8,300 km²) for
IFAD coverage depends on project phase – is this correct?
Phase 1 ( ): 3,200 km² (4 northern communes of Tsivory, Elonty, Mahaly and Marotsiraka)
Phase 2 ( ): 8,300 km² (11 communes)
EOFI
Reduction to 4 communes of PHBM-I leads to a decrease from 8,943 ha to 5,290 ha irrigated land
Sources:

5. EOFI Service Trial 1: UN-IFAD – Crop Acreage
#2: How shall the IFAD area figures be interpreted?
Was IFAD’s 4,169 ha increase achieved by establishing new irrigated land or by rehabilitating existing irrigation schemes or both?
Where does the 1996 value (1,061 ha) originate? Is our assumption correct, that this value only represents actively managed irrigated land?
An UNOPS mission report of PHBM-I states 3,200 ha of irrigated rice fields for 1996 – how does this relate? See below IFAD weblink
Has the area of 5,230 ha irrigated land for 2007 been measured with terrestrial methods?
Terrestrial field measurements provide more accurate area figures, but are more expensive and time-consuming
Sources:

6. EOFI Service Trial 1: UN-IFAD – Crop Acreage
#3: What exactly is measured?
IFAD reports 32 irrigation schemes rehabilitated from and further 39 from (total: 71), leading to an area of 5,230 ha irrigated land:
Does this figure represent the irrigated land from 71 rehabilitation projects or the total irrigated land in the entire PHBM area?
Is it valid for the PHBM-I or PHBM-II area?
Selected locations of rehabilitation projects (Perimétres irrigués)
PHBM evaluation report states that only larger irrigation schemes are adressed:
“Petits Perimetres irrigues” (PPI) larger 100ha
“Microperimetres irrigues” larger 10 ha
Is this correct?
Satellite-based monitoring detects much smaller cropland patches with an object size of > 1ha – thus increasing the total mapped area
Sources:

7. EOFI Service Trial 1: UN-IFAD – Crop Acreage
#4: What about rice fields under dry conditions and irrigated cropland in remote locations?
Main focus on the PHBM projects were irrigated rice and crops
Do the area statistics only cover managed irrigated land or also dry rice fields or abandoned irrigated land?
PHBM evaluation reports state the “inaccessibility of the project zone” and the “insufficient coverage of villages outside the main towns”
Are existing rice fields and other irrigated cropland in remote regions covered?
Irrigated cropland in remote location
Dry / abandoned rice field
Sources:

8. EOFI Service Trial 1: UN-IFAD – Crop Acreage
#5: Information content of available data not optimal for detecting small-scale irrigation structures
Poor availability of multi-temporal / multi-polarisation radar data
Sometimes ambiguous differentiation of crop types due to imagery from different seasonal dates (dry vs. wet season)
Limited availability of ground-truthing data
EO imagery used for mapping
High-res imagery for validation
 Technical infrastructure for irrigation (incl. dams, narrow water channels) not visible in 10-30m satellite imagery
 Irrigated cropland contains actually irrigated cropland PLUS in many cases also potentially irrigated cropland predominantly along water courses

9. EOFI Service Trial 1: UN-IFAD – Crop Acreage
#6: Resulting area statistics have a defined level of reliability with known error margins
Error margin of area statistics
Requirement
Achieved accuracy
Rice
90%
80-85%
Irrigated crops
n.a.
60-70%
Rainfed crops
70%
70-75%
Forest
80%
>85%
Grassland
Bare area
Urban
Water
Margin 15-20%
Margin 30-40%
Overall accuracy: 80-85%
Validation analysis shows a slight tendency towards overestimation of rice and irrigated crops
- high level of completeness
- lower level of correctness

10. EOFI Service Trial 1: UN-IFAD – Crop Acreage
Summary of evaluation – assumptions
Direct comparison of area figures is hardly possible
Assumptions need to be verified in collaboration with IFAD
IFAD
Satellite-based monitoring
1996
1,061 ha
(PHBM-I area)
Existing managed irrigated land
5,290 ha
Managed + abandoned + potentially irrigated land + dry rice fields
All patches > 1 ha
2007
5,230 ha
(PHBM-II area)
Managed irrigated land from rehabilitation projects > 10 ha
11,612 ha
Could the outline of the areas surveyed by IFAD be delivered?
Shall we eliminate all patches <10 ha and re-compare?