Observations and Measurements

Transcription

1 Observations and Measurements issues and upgrades Simon Cox CSIRO Exploration & Mining

2 Goal of Observations and Measurements Information model for Sensor Web Enablement consistent with Measurement Theory GML encoding for observations consistent with OGC Feature Model Examples for implementers 5/09/2003 2

3 The Observation Feature 5/09/2003 3

4 Views of the same information 1. Observation event 2. Coverage aggregate values one observation, vector result coverage = composite results of many observations 3. The target feature many observations on a single subject values of many properties These views may be obtained by suitable transformation of the same source information 5/09/2003 4

5 A Coverage Feature may be an observation Coverage == Observation with extensive target result varies across target other observation properties constant == coverage metadata Typical view of frame cameras surveys of time-invariant phenomena 5/09/2003 5

6 An observation array may form a coverage Observation-array Observation location time Value component Value component Value component Value component represents the information in row-order Multi-geometry or Grid + Value Array (of vector values) Discrete coverage represents it in column-order Observation array == Coverage complementary views each (position,value) pair could be modelled as a Feature 5/09/2003 6

7 Observations may evaluate Feature properties A Feature has many properties Observed phenomenon == Property name Result of an observation == property value Other observation properties == metadata for a single property value Should procedure, quality, etc be packaged for easy re-use in this context? Visible via WFS? 5/09/2003 7

8 Information models and service interfaces An information model addresses a particular point of view or context Observation = data collection event, procedures and quality Coverage = data analysis, anomaly (i.e. feature) detection Feature = description of an object in the world Each information model might have a corresponding service interface SCS, WCS, WFS the operation signature should match the information model systematic design technique? 5/09/2003 8

9 The Observation Feature SWE-services should exploit the relevant information model SCS operations should mirror the components of an observation feature Do they?? 5/09/2003 9

10 Measurements vs observations Conventional wisdom: distinguish evidence vs. inference Objective measurements made by sensors and instruments, from interpretations and classifications made by algorithms and people But: is any measurement truly primitive? temperature vs length, resistivity, brightness generalise sensor procedure procedure = algorithm + inputs Use a single observation model regardless of position in processing chain Observation act of estimating a value of a phenomenon, involving a procedure, instrument or algorithm 5/09/

11 Harmonisation with external standards Vocabularies for observables, units, reference systems UCUM definitions and codes for uom units & kind of quantity e.g. meter, length EDCS (ISO 18025) vocabulary for Environmental Data attributes and their equivalence classes e.g. wavelength, length Classifications e.g. Glacier, Golfcourse, Guided Missile Destroyer units, quantities, and their equivalence classes e.g. meter, mean-free-path, length EDCS metamodel can be partially mapped to Feature model, O&M Nothing comparable to O&M constrained and composite phenomena 5/09/

12 Some other issues Harmonisation with WCS Phenomenon + scale encoding needed to serve as range-parameters description scale associated with scalar, base phenomena Dimensionality of phenomena Sequence rules for associating result components with composite phenomena + composite target components Tuples & tables could follow GML pos-crs pattern More work on reference systems needed CRS GML CRS schemas uom GML units.xsd, UCUM nominal & ordinal GML dictionary.xsd, other lists?, hierarchical systems? 5/09/