scope:

This document presents guidelines for testing z-axis (i.e., altitude) accuracy for systems that use barometric pressure-based sensors in the handset. Focus is placed on systems where the measured altitude is derived from compensated barometric pressure measurements, i.e., where the error sources in the pressure measurement are compensated for by the location system under test and where the altitude result is expressed in units of distance, i.e., in meters, rather than a raw measurement in units of atmospheric pressure, e.g., hectopascal or millibar.

This document clearly identifies the various salient sources of barometric pressure measurement errors and proposes test methods that ensure that those effects are accounted for in the design of the tests and that their effects are manifested in statistically representative test samples.

Non-barometric pressure z-axis or altitude measurement systems, which are currently less likely to be relied upon in the near to intermediate term, or are less mature than barometric pressure systems are not addressed in this document, and they may be addressed in future ATIS test methodology standardization efforts as the need arises.

Purpose

The purpose of this document is to provide broad guidelines for testing barometric pressure-based altitude (zaxis) measurement systems, which are being proposed to enable more accurate and more actionable indoor wireless 911 location. This document is not intended to provide detailed test procedures but rather creates the framework upon which such detailed, technology specific z-axis test procedures can be readily developed. A primary purpose for this document is to enable technologist, wireless carriers and test organizations to create consistent, representative test procedures that appropriately capture the key environmental and operational effects impacting the accuracy of altitude (z-axis), barometric pressure-based solutions in the context of indoor wireless E911.