THERE'S AN APP FOR THAT... TESTING GEOLOGIC SMARTPHONE APPS AGAINST THE BRUNTON POCKET TRANSIT

In geological mapping, attitudes of rock strata are described by measuring strike and dip. In the field, the locations and attitudes of strata can make measurements difficult, even dangerous, to make. Recently, smartphone apps have been developed that take strike and dip measurements quickly and easily, and even map them using GPS with the option to include notes or photographs. This has provoked debate among geologists as to their utility, especially regarding the quality of the measurement. It is expected that a conventional magnetic compass will be more precise, as well as accurate, but there is an argument for being able to take measurements quickly and easily, especially in physically challenging situations. Since the app reads the phone’s accelerometer to orient itself, the choice of app should not influence the results, but the device itself may. Therefore, we tested one application each on an Android phone, an iPhone, and an iPad for accuracy and precision versus the Brunton compass. Results confirm that the compass gives more precise results when used correctly. While the precision of the compass is to be generally preferred, these tests also show that the variance in readings given by the app can be acceptable for geologic mapping, where the natural variability of plane orientations often exceeds the error of the mobile phone. This is expedited by the app’s ability to make many measurements quickly, as well as its virtually nonexistent learning curve. While it is unlikely that the compass will soon be replaced, the speed, convenience and safety offered by the smartphone app are appealing enough to warrant its use in certain situations.