Tru-Path

Row, row, row your boat gently up / down the stream???

Purpose: This blog post is created to help readers a) better understand electronic compass [smartphone or rangefinder] residual azimuth deviation errors b) quantify the errors, c) model the errors, d) compensate for [correct] the errors, and e) influence the app vendors to apply the correction method within their own affected smartphone app. Basically, we need to know (accurately) whether to go up / down the stream (path) we are traveling on.

Goal:  The goals of this blog post are to prove a) the usefulness of an accurate smartphone compass app for practical applications, b) the manufacturer’s recommended calibration procedures work just fine to address/correct errors due to magnetic influences within the phone itself, c) residual [after calibration] smartphone compass deviation errors exist due to external/environmental magnetic influences beyond the reach of the calibration procedures, and d) residual compass azimuth deviation errors can be corrected [effectively compensated] to provide “just-good-enough” compass azimuth accuracies sufficient to “get-the-job-done” – in all but the most demanding circumstances.

Background:

This post introduces and presents the Android / TruPath Compass recommended compass calibration procedure.  TruPath Compass is the ONLY smartphone compass app that compensates (corrects) residual azimuth deviation errors – at this time.

If you’ve ever used a smartphone compass app, you have experienced azimuth errors.  Smartphone compass apps are notoriously inaccurate!  This fact is well documented over the past several years.

Also, like thousands of other users of smartphone compass apps (as evidenced by user complaints/questions on multiple internet forums) you have sought answers about how to “correct the azimuth errors”.  TruPath Compass provides the answer for correcting smartphone compass azimuth errors – residual (after calibration) azimuth deviation errors.  The answer comes in a two parts.

• Perform the recommended smartphone compass calibration procedure – as needed.
• Use the TruPath Compass app to identify, quantify, resolve, and compensate those residual azimuth deviation errors caused by external environmental influences – beyond the reach of the calibration procedures.

Internet “experts” have recommended everything from a) using the well-known “figure 8” pattern (fast; but just-good-enough) to b) some more effective multi-step process of rotating about the three [3] principal axes of the smartphone – to even more elaborate 3-step or even 11-step processes; which do not work for correcting residual azimuth deviation errors.  In fact, all the “expert recommended” processes ONLY deal with the calibration/re-calibration of the smartphone with respect to the internal placement of the components of the smartphone itself – and to some minor extent those magnetic/electromagnetic influences which may exist on (or in the immediate vicinity of) the person of the user.

To be certain, the digital compass within your device needs to be recalibrated regularly.  It is a 3-axis sensor that measures the magnetic field around us. You should recalibrate it after charging, travelling in a vehicle, or leaving the device stationary on a desk for any appreciable amount of time.

To recalibrate, rotate the device about each axis 2 or 3 times to detect the min and max field strengths.  Each rotation should take 3-5 seconds. When using the digital compass, avoid areas where there are likely to be extraneous magnetic fields (e.g. adjacent to power lines, transformers, vehicles etc.).  To be safe, use the TruPath Compass app to work in conjunction with the recalibration procedure and compensate errors associated with these extraneous magnetic/electromagnetic influences.

Recommended Calibration / Recalibration Procedure

• Orient yourself so that you are facing north, roughly aligned with the earth’s magnetic field.
• Using portrait (orientation) mode with the display facing towards you. Imagine an axis extending to the left and right parallel to the screen. Rotate about this horizontal axis.
• Using landscape (orientation) mode with the display facing towards you. Imagine an axis extending to the left and right parallel to the screen. Rotate about this horizontal axis.
• Using portrait (orientation) mode with the display facing to your right. Imagine an axis extending to the left and right orthogonal to the screen. Rotate about this horizontal axis.
• Finally, hold your device flat with the display facing up. Imagine an axis extending vertically upwards through the center of the screen.  Rotate about this vertical axis.

You should be rewarded for your calibration efforts; and you should receive the best performance possible from your smartphone sensors – but alas, these have little regard for the existence of residual (after calibration) azimuth deviation errors caused by external environmental influences.  TruPath Compass provides a feature which indicates the calibration health (status) of the smartphone’s calibration status – good and not-so-good.

Take advantage of TruPulse Compass’ ability to identify, quantify, resolve, and compensate those residual azimuth deviation errors.  Your operational status will be the best it can be.

Conclusions:

• The TruPath Compass app is intended to work in conjunction with good vendor-recommended calibration/recalibration procedures (which deal with the internal placement of the device’s sensors).
• The TruPath Compass app is intended to compensate residual (after calibration) azimuth deviation errors caused by external environmental influences.
• The TruPath Compass app is easy-to-use in either handheld or tripod-mounted data collection methods.
  • The TruPath Compass app (currently in prototype/beta test versions) requires about 4 minutes to collect the “measured” azimuth readings necessary to identify, quantify, resolve, and compensate residual azimuth deviation errors – very efficient.
  • The TruPath Compass app can be effectively used by younger (less experienced) and older (more experienced) individuals – it’s quite intuitive to use.
• The TruPath Compass app can be used over a wide range of geographic locations – in both the northern and southern hemispheres.
• The TruPath Compass app makes the smartphone “compass survey” method plausible in field data collection situations.
• The TruPath Compass app (once released) will be capable of:
  • Compensating residual (after calibration) azimuth deviation errors for its host smartphone.
  • Determining the necessary compensation parameters for any third-party smartphone compass app; and these compensation parameters will be available for correcting the third-party compass app’s residual azimuth deviation errors – if the third-party vendor elects to do so.
  • Determining the necessary compensation parameters for any third-party rangefinder compass; and these compensation parameters will be available for correcting the third-party rangefinder compass’ residual azimuth deviation errors – if the third-party vendor elects to do so.
  • Determining the necessary compensation parameters for any third-party electronic compass; and these compensation parameters will be available for correcting the third-party electronic compass’ residual azimuth deviation errors – if the third-party vendor elects to do so.

Preview: In upcoming blog posts, the author will deal with the accuracy (or lack thereof) other Android/iPhone compass apps.  As with previous tests involving the Android/iPhone compass apps, the same rigorous methods will be used to collect, analyze, and present the results.

The next blog post is planned to deal with the Android/TruPath Compass app’s repeatability when collecting “measured” azimuth data.  Also, in the near future, the author plans to deal with the issue of compensating residual azimuth deviation errors in crowded parking lots and other areas where significant magnetic/electromagnetic influences exist.