The Use of the International Hydrographic Organisation's 'Standards for Hydrographic Surveys' As a Measure of Depth Accuracy in Continental Shelf Determinations

Article 76 of UNCLOS requires the determination of depths of 2,500m to establish the position of one of the two alternative components of the Outer Constraint to the Continental Shelf. Recognising the water depth’s possible role, the Guidelines produced by the Commission on the Limits of the Continental Shelf (CLCS) specify the types of depth-measuring instrumentation that can be used, the types of analysis to transform bathymetry data into a bathymetric model, and the type of database and supporting information to be provided. Included in the latter is the requirement to provide A priori or a posteriori estimates of random and systematic errors’, where a priori errors may be calculated using the International Hydrographic Organisation's (IHO's) S44 Standard for Hydrographic Surveys. Having the CLCS refer to this internationally accepted standard as the most appropriate for UNCLOS purposes imposes a responsibility on the IHO to ensure that S44 does provide an appropriate, up to date and achievable standard for 2,500m water depths. This paper shows how S44 could be revised to make it fully suitable for this new task, one that for which it was not originally designed . S44 defines total error as the Root Sum of Squares (RSS) of the constant and variable depth errors. Marine areas are divided into zones according to their use by surface shipping, and a table provides the values to be substituted in the RSS equation for each area. While this approach has proven useful for transportation purposes, it is not necessarily applicable to deep-water contours, in that it does not take into account the magnitude and impact of the many factors that influence the uncertainty of location of deep water contours. These differ greatly in their magnitude and influence as the sea floor deepens beyond navigation depths, and are explained in this paper. We conclude with a firm suggestion to the IHO to undertake production of a new edition of S44 and include information on how it can be expanded to become more applicable to deep water

Validation of a Scale to Measure Patient-Perceived Barriers to Medication Use

AIMS: Medication adherence may explain why patients show very different clinical outcomes. Previous assessments of adherence have used refill rates and pill counts. Few studies have investigated patient-identified barriers to using medications as prescribed. This is particularly true for persons with diabetes, most of whom are using poly-pharmacy regimens. We created a questionnaire to measure patient perceptions of barriers to medication adherence (PBMA) targeting a predominately low income, inner-city minority population. METHODS: Twenty items (Likert scale) leading with "I sometimes don't take my diabetes medicines because..." were developed from 5 focus groups (N=48). A questionnaire including these items was mailed to 1000 patients who have diabetes. RESULTS: Using data from 267 respondents (Mean age=58, 74%female, 43% non-Hispanic Caucasian, 77% income<$15,000), exploratory factor analyses with varimax rotation identified 5 factors, that may contribute to poor medication adherence: personal access to medications (F1); communication with providers (F2); understanding or appropriately following the prescribed regimen (F3); side effects (F4) and system factors that inhibited access to medication (F5). Cronbach alphas ranged from .73 to .83 for the five factors and was .92 for total scale score. No relationships were found between total scores and gender, race, or income. Greater perception of barriers was significantly (p<0.01) associated with being younger (r= -0.21), being bothered more by physical (r= -0.40) and emotional side effects (r= 0.43), and less satisfaction with control of blood sugar by diabetes medications (r= 0.45). CONCLUSIONS: This instrument is reliable, factorially valid, and consistent with clinical observation regarding factors known to be associated with patient medication adherence. Although study participants were patients with diabetes, the PBMA may be applicable to other therapeutic areas

Introduction: Surveillance Studies as a Transdisciplinary Endeavor

Introduction to Surveillance Studies: A Reader