Item I. Inconsistent photography

The use of consistent photography is a crucial factor in providing a precise estimate of wetland loss. Due to lack of availability, two types of photography had to be used to analyze the study area—Lamberts and DOQs. This posed the problem of inconsistent time frame comparisons. The portion of the study area using the lamberts compared an approximate 7-8 year wetland difference. The DOQs, on the other hand, were flown in 1995. This provided only a 2 year wetland difference. This difference became very obvious during analysis. There are seven years of development missing from the eastern portion of the study area. This factor can be assumed to have minimized the estimate of wetlands loss.

Item II. Water intrusions due to subsidence

The amount of wetlands loss by water intrusion due to subsidence cannot be determined from this study. In order to estimate this loss, the reference photography (DOQs and Lamberts) would have to be taken at the same tide level, season, lunar cycle, etc., as the original photography the NWIs were developed from. This is a virtually impossible task using remotely sensed data.

Item III. Scale differences

Scale differences between the original photography used to develop the NWIs and the reference photography (Lamberts and DOQs) created a conflict with varying levels of detail. The NWIs were developed from 1:65,000 scale photography. Digitizing from this scale of photography cannot produce the same level of detail that can be derived from the larger scale Lamberts and DOQs. This made it difficult to differentiate between wetland loss and digitizing errors from the use of small scale photography when the NWIs were developed.