The listerCompass is an advanced compass designed to allow a field geologist to take advantage of the iPhone's capabilities.
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Orient the compass with the bottom of the compass parallel to the surface you want to measure.
If you are under an overhang, hold the compass upside down.
The same reading should be obtained.
Hold the long edge of the compass parallel to the trend of any lineation or striation you want to measure. It does not matter whether the compass points up along the lineation or down. The answer should be the same.
Once it stabilizes, hit "Stop" or tap the screen. Double tap to record the data. Data is collected, averaged, and presented in a standard format (mean ± standard deviation). If the error is too large, then repeat the measurement. Data is provided relative to magnetic north - because you can always add the declination later.
If you want to measure a surface, put your iPhone anywhere on it.
If you want to measure the surface, and a lineation on that surface, orient the iPhone on the surface so that it is oriented with its long axis parallel to the lineation.
To measure both together place the iPhone on gthe surface, with its long edge parallel to the lineation. Upside down is also OK.