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Experience with GPS Technology for Area Estimation in Agriculture: Validation & Conclusions

Learn about using GPS technology in agriculture for area estimation, validation, and conclusions drawn regarding tool accuracy and efficiency. The text delves into the West Shoa area frame project's experiences with GPS and GNSS technology and the validation of the tools used.

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Experience with GPS Technology for Area Estimation in Agriculture: Validation & Conclusions

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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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