Timing and frequency. Repeat photography visits should be conducted on days with favorable weather and good visibility and should coincide with the late-summer end of the ablation season when the maximum area of snow-free ice is exposed (Fountain et al., 1997). Under ideal circumstances, terminus monitoring and mapping should occur on an annual basis. If yearly photography is not practical, monitoring should generally occur on a five- to ten-year schedule. It is important to note that the terminus position of calving glaciers can change significantly over a brief period and may require a shorter (one- to five-year) monitoring interval (Post, 1975). Conversely, a longer (five- to ten-year) monitoring interval may be adequate for small cirque glaciers (Fountain et al., 1997). If significant changes are observed during the interim period between monitoring visits, a more frequent monitoring schedule may be appropriate. Timing and frequency. According to Fountain et al. (1997), satellite or aerial photographic surveys should occur “late in the summer so the terminus will be in its most retracted position; the transient snowline nearest its final, seasonal position; and the accumulation- rea ratio at its seasonal minimum.” The satellite or aerial surveys should generally be conducted on a five- to ten-year schedule. It is important to note that the terminus position of calving glaciers can change significantly over a brief period and may require a shorter (one- to five-year) monitoring interval (Post, 1975). Conversely, a longer (five- to ten-year or longer) monitoring interval may be adequate for small cirque glaciers (Fountain et al., 1997).
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