- From: Rick Waldron via GitHub <sysbot+gh@w3.org>
- Date: Tue, 08 Nov 2016 21:23:34 +0000
- To: public-device-apis-log@w3.org
> temperature of the pressure sensor in an altimeter Can you give an example of this? I've implemented drivers for many sensor packages that include temperature, pressure and altitude and I don't recall encountering anything like "temperature of the pressure sensor in an altimeter"—but I obviously haven't worked with _every_ sensor package. Generally, an altimeter uses barometric pressure to calculate the altitude: pressure at sea level, the pressure as measured by the barometer at the place being measured, and the temperature at the place being measured. These three values are then used to produce the altitude/elevation _from sea level_. To get the relative local altitude, the present geographical elevation must be known; eg. I'm on the top floor of a 100 story building in Denver, Colorado: the relative local is just the 100 stories, and does not the geographic elevation. (I'm not really on the top floor of a 100 story building in Denver, in fact: no such building exists). On the other hand, `bias` is an interesting data point. [In the recent discussion about raw magnetometer readings](https://github.com/w3c/magnetometer/issues/16), it was implied that the individual bias for each axis would be available, however that't not true for all magnetometer platform APIs (as later stated by @riju) or ICs on the market. For example, the HMC5983 has a two configuration bits that allow setting one of two bias modes (negative or positive) that are handled by the IC itself (ie. it will apply a positive or negative bias current across the axis). If a device is made with that chip, or similar, then bias defined as a value that is "measured" is not something the sensor is aware of. -- GitHub Notification of comment by rwaldron Please view or discuss this issue at https://github.com/w3c/sensors/issues/151#issuecomment-259263942 using your GitHub account
Received on Tuesday, 8 November 2016 21:23:40 UTC