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West Shoa area frame project – experiences in using of the GPS technology for area estimation

West Shoa area frame project – experiences in using of the GPS technology for area estimation. Experiences in using of the GNSS technology in agriculture in Europe. In the presentation. Agriculture Unit Area-based subsidy in Europe - numbers Why to test tools?

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West Shoa area frame project – experiences in using of the GPS technology for area estimation

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  1. West Shoa area frame project – experiences in using of the GPS technology for area estimation Experiences in using of the GNSS technology in agriculture in Europe

  2. In the presentation • Agriculture Unit • Area-based subsidy in Europe - numbers • Why to test tools? • Validation of the tools on example of Garmin GPS72 • Conclusions

  3. Who we are? MARS-PAC (GeoCap) → Direct Payments to Farmers FOODSEC ↓ Crop monitoring outside EU Agri4Cast ↓ Crop Yield Forecasting for EU

  4. Area-based subsidy controls in 2008 GeoCAP (MARS PAC): Compliance and Control of Area-based subsidies in Agriculture and Regional Policies • 8.6 Million applications for 155 Million ha in 27 MS • area of ~12.8 Million hectares controlled/measured • 8.1 Million hectares measured on the satellite images (CwRS) • 4.7 Million hectares measured in the field using GPS receivers, tapes and other tools

  5. Introduction: Area measurement validation scheme • Purpose of the scheme • to define an approach for the validation of area measurement methods for agricultural parcels, • mainly using (but not restricted to) GPS equipment. • Motivation • The availability of relatively low-priced GPS tools • However, both the EC and Member States need assurance that the tools on offer are able to perform to acceptable standards.

  6. Why validation? • Assessment of precision of the tool (random error) • Assessment of accuracy of the tool (a systematic error) • Evaluation of the time effectiveness of the tool • Feeling on a general performance of the tool (practical issues, batteries life etc.) Decision: is the tool suitable for the needs of the project?

  7. Assessment of precision and accuracy of Garmin 72. Test design West Shoa area frame project – experiences in using of the GPS technology for area estimation.

  8. With what we measured? Garmin GPS 72 GeoXT -Trimble

  9. Test site 6 fields – representation of the landscape(shape, size, obstructions of horizon (borders)) • Flat ~0.31 ha • Flat ~0.04 ha • Moderate slope ~0.15 ha • Forest on a slope ~0.10 ha • Steep slope, border with a forest ~0.21 ha • Flat ~0.57 ha

  10. Field A: ~0,31ha, flat

  11. Field B: ~0,04ha, flat

  12. Field C: ~0,15ha, moderate slope

  13. Field D: ~0,10ha, Forest on a slope

  14. Field E: ~0,21ha, steep slope, border with the forest

  15. Field F: ~0,57ha, flat

  16. Artificial borders clearly marked:

  17. How to measure? How many times?: 5 runs with 4 repetitions = 20 measurements of one field with one receiver When?: 1 run 4 measurements in row for a field = repeatability conditions (influence of the satellite system limited) runs should start at different time of the day = reproducibility conditions (influence of the satellite system taken into account)

  18. Practical issues: • Within one run walk clockwise and anti-clockwise, • Try to have one operator per field, • Make the border of the field comfortable for walking, • GPS receivers give the projected (horizontal) area, • GPS area measurements are only comparable with rope & compass on flat fields!!!

  19. Statistics • Reference area (GeoXT with data post-processing) • Outliers detection (Grubbs’ and Cochran’s tests) • Repeatability standard deviation • Reproducibilitystandard deviation • Bias of the measurements • Additionally: ANOVA to analyze influence of factors like: operator, field, size, border type etc.

  20. Assessment of precision and accuracy of Garmin GPS72

  21. Conclusions: • The CSA have capacity to design and run validation tests of the GNSS receivers, • Garmin GPS72 is a user-friendly tool, easy to handle even for absolute beginners, • Garmin GPS 72 seems not to give any significant systematic error with random errors (1σ) below 3.4% for fields >0.2ha, • Time-efficiency has been proven during the tests (up to 20 fields per hour)

  22. Conclusions: • Impact of usage of the projected area instead of the sloped should be analyzed, • Storing results of the measurements in a database could benefit and support spatial and temporal analysis of the data • Other GNSS receivers owned by the CSA should be tested before using them for area measurements.

  23. Thank you for your attention!

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