Altitude 'Dead Reckoning' for Casio Triple Sensor v.3
DR-Altimeter predicts how much the indicated altitude will deviate due to changing weather in the vicinity of a Wunderground.com station. By subtracting the predicted altitude change, to remove its influence, one can greatly improve the accuracy of the Casio Pro Trek wristwatch altimeter. Depending on the accuracy of the weather forecast, the indicated altitude can follow true altitude well within a ± 5 meters error margin.
- Fully configurable with an .ini file
- Predictions both produced in graphical and text format
- Adaptive multilingual interface. English [en] and français [fr], so far
- Text results can be automatically posted to a Slack chat room, therefore to a smartphone
- Command line options, useful notably to create shortcuts and scheduled tasks (Windows equivalent of a cron job)
- Graphical User Interface (GUI) with zoom and pan functions, to export portions of the graph that interests you specifically
The altimeter determines the altitude at your current location based on accumulated atmospheric pressure changes measured by the pressure sensor. Setting the altimeter at a location where you know the precise altitude before starting your ascent enables it to take even more precise altitude measurements.
Setting the altimeter at a location where you know the precise altitude enables you to determine the elevation of your current position with respect to sea level. If you come across a marker indicating 400 meters above sea level while hiking or climbing, for example, simply set the altimeter at 400 meters. This enables you to obtain more accurate readings with respect to sea.
Dead Reckoning is the process of calculating one's current position by using a previously determined position, or fix, and advancing that position based upon known or estimated speeds over elapsed time and course.
Altitude dead reckoning uses the same principle as dead reckoning but applies it to the vertical plane. Whilst standing still at a fixed altitude, you'll notice that the altimeter perceives atmospheric pressure variations due to weather changes as altitude changes as if you climbed or descended. DR Altimeter displays in brackets [] the expected contribution of weather changes to the indicated altitude.
H PRESSURE ALT ALT/hr
===============================================================================
13h05 1019.98 hPa 13h12[fix], 13h29[1], 13h56[2]
-------------------------------------------------------------------------------
14h 1019.80 hPa 1.5m 1.5m 14h20[3], 14h43[4]
-------------------------------------------------------------------------------
15h 1019.50 hPa 4.0m 2.5m 15h07[5], 15h33[6]
-------------------------------------------------------------------------------
16h 1019.20 hPa 6.5m 2.5m 16h05[7]
-------------------------------------------------------------------------------
17h 1019.00 hPa 8.1m 1.7m 17h04[8], 17h35[7]
-------------------------------------------------------------------------------
18h 1019.10 hPa 7.3m -0.8m 18h34[6]
-------------------------------------------------------------------------------
19h 1019.40 hPa 4.8m -2.5m 19h05[5], 19h30[4], 19h52[3]
-------------------------------------------------------------------------------
20h 1019.61 hPa 3.1m -1.7m 20h14[2], 20h35[1], 20h57[0]
-------------------------------------------------------------------------------
21h 1019.87 hPa 0.9m -2.2m 21h21[-1], 21h52[-2]
-------------------------------------------------------------------------------
22h 1020.20 hPa -1.8m -2.7m
At 13h12, you determine that you are at a known altitude of 450 meters above mean sea level. This is your reference or initial [fix].
13h12[fix] = 450m ASL
Later, at 13h56, your watch indicates an altitude of 476 meters. And since, between 13h12 and 13h56, the expected contribution of weather is 2 meters (see Figure 2), you can estimate your true altitude to be 476 - 2 = 474 meters above sea level.
13h56[I] = 476m, indicated
13h56[DR] = 476m - 13h12[2] = 474m ASL, compensated for forecasted weather
On the same trek (see above), at 19h52, you reach a point of known altitude (523m ASL). You recalibrate your watch to match this known altitude. Here and on after, this new [fix] becomes your new reference.
19h52[fix @ 3] = 523m ASL
Later that evening, at 20h22, your watch indicates an altitude of 478 meters. Since your last fix was taken at the [3] compensation level (19h52[3]) and you are current at the [2] compensation level (20h22 ≈ 20h14[2]), your deduced altitude is 478 + @[3] - [2] = 479 meters.
20h22[I] = 478m, indicated
20h22[DR] = (478m + @ 19h52[3]) - 20h14[2]
= 481 - 2
= 479m ASL, compensated for forecasted weather
See INSTALL.md
See CONFIG.md
See COMMAND.md
- Walter Wlodarski - Creator - Wlodarski
This project is licensed under the MIT License - see the LICENSE.md file for details
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