Figure 5: Example of impact of field of view shifts on camera imagery and derived GCC time series for a site with mixed vegetation.
From: Tracking vegetation phenology across diverse North American biomes using PhenoCam imagery
Field of view shifts in imagery (site: “monture”, Lolo National Forest, Ovando, Montana, year: 2004) were detected on April 20 (day 111), September 8 (day 252), October 5 (day 278), November 3 (day 308), and November 23 (day 327). (a-c) Sample images are from April 16, May 6, and October 23. Note the changing position of the small, evergreen conifer right of centre. (d) Composite image, in which field of view shifts are easily identified. Asterisks along the bottom of the image denote the dates of the 5 shifts that were detected. (e) Time series of GCC, the green chromatic coordinate, showing the difference in the inferred grassland seasonality when the region of interest (ROI) mask is corrected for shifts in the field of view. The corrected mask includes only grassland vegetation, while the uncorrected mask includes a mix of grassland as well as deciduous or evergreen tree foliage. Artifacts are visually apparent in the data derived from the uncorrected ROI mask. The y-axis ticks and labels have been omitted from (e) to facilitate alignment with (d). The y-axis range is approximately 0.32 to 0.44 GCC units.
