## 3 Results
### Relationships between Time-Series SAR Signatures and the Timing of Field Activities
Using the aforementioned interpretation rules, the seeding date for the barley field was determined to be between May 6 and 18, because coherence of the pair of SAR images acquired on these two dates was much lower (\(-\)0.23) than that of the next image pair (\(-\)0.56), acquired between May 18 and 30 (Figure 6a), which indicated that a great change (i.e., seeding) had happened between the first time window. The harvest date for the field was between August 10 and 22 because there was a big increase in coherence from 0.22 for the August 10 and 22 image pair to 0.44 for the August 22 and September 3 image pair, suggesting that the change (harvest) happened in the first time window. This is in conformity with the observed seeding date on May 18 and harvest date August 15, respectively. In accordance to the low coherence for the August 10-22 InSAR pair, the VH dropped greatly during this period. The low-high coherence transition was also observed afterwards, between September 3 and September 15, and between September 27 and October 9. By referring to the field photo (Figure 7a), we speculate that residue removal might have happened during this period. For the canola field, the observed seeding date was within the time window (May 5-18) determined from time-series InSAR coherence, whereas the observed harvest date (September 9) was earlier by one satellite repeating cycle than the window with the largest InSAR coherence increase (September 15-27 from 0.21 to 0.69) (Figure 6b). It is possible that there is inaccuracy in the reported harvest date by the producer. The smaller InSAR coherence increase during the mid-season is not well understood and will require further study with the  
Figure 7: Pre-harvest (**a–b**) and post-harvest (**c–f**) photos for the four example fields shown in Error! Reference source not found. Note: no photo was taken in the soybean and canola fields before harvest. support of detailed field observations. For the soybean field, the observed seeding date (May 13) was within the SAR image pair May 6-18, whereas the harvest was captured by the third InSAR coherence increase after late July, i.e., the SAR pair September 27-October 9 (Figure 6c). VH could be inspected to preclude the SAR pairs of July 29-August 8 and September 3-15, based on their relatively higher backscattering coefficients. For the oats field (Figure 6d), VH was large on May 6 and decreased to a lower level on May 30, while coherence increased from May 6 to May 18, and dropped to the lowest level on May 30. This suggests that seeding could have happened during the May 30-June 11 time window, in conformity with the observed seeding date on June 6. It is likely that the field either had cover crop or significant amount of standing residue left from the previous season before seeding. The observed harvest date (September 25) was between the September 15 and 27 time windows. Given the small increase of InSAR coherence (0.04) and a relatively higher level of VH (\(-\)14.2 dB) and VV (\(-\)9.4 dB), harvest could be during this period, but with less confidence in interpretation.