The middle of the app's main screen displays a compass, with multiple display and unit options (see "Preferences" below). In all modes, the compass shows both magnetic and true bearing. The outer true ring is automatically adjusted for local magnetic declination.

Tapping once on the center of the compass will set a yellow marker, known as a compass "bug", for the current bearing. To clear the bug, double tap the center of the compass. This bug comes in handy when you need to mark and/or follow a bearing of interest for navigational purposes.

The top part of the app's main screen displays bearing information, giving both magnetic and true bearing in degrees, mils, and quads. In the middle of the bearing display, under the compass arrow, the current magentometer hardware accuracy is shown.

The bottom part of the app's main screen displays GPS information, including position and altitude, as well accuracy for both.

Under the bearing display, two dials display vertical (V) and horizontal (H) inclination in degrees. The vertical angle refers to the angle between the long axis of the device and a level reference (i.e., tilt front to back to vary vertical angle). The horizontal angle refers to the angle between the short axis of the device and a level reference (i.e., tilt side to side to vary horizontal angle). The compass dial contains two independent bubble levels corresponding to vertical and horizontal inclination as well as a combined bullseye level.

Tap the "PREF" button in the lower right corner of the screen. The app includes settings for the compass style, compass units, length units (used for altitude and position/altitude errors) and position format. The preferences section also provides access to inclinometer calibration and this help page.

Tapping the "MAP" button will bring up a map with standard, satellite, and hybrid view options. An arrow button in the lower left corner will center the map on the current location. Access to map tiles requires an internet connection.

Pro Compass 1.1 introduced an optional Datum Pack, which adds over 230 new geodetic datums to the app, covering regions around the world. These datums are used to compute position from GPS data. The Datum Pack is available with an additional one-time in-app purchase of $2.99 (or equivalent) through the App Store.

The default datum used by iOS location services, and Pro Compass, is WGS-84 (WGS stands for "world geodetic system" and 84 refers to "1984", the year of this standard). WGS-84 is an ellipsoidal model that approximates the surface of the Earth.

While WGS-84 is a good worldwide compromise for a datum, any datum that attempts to model the entire Earth with a single ellipsoid will have errors in regions where the Earth's actual surface deviates from the ellipsoidal shape. For that reason, local datums are often used in navigation and surveying. These allow a more accurate representation of the Earth surface over smaller regions of interest. Well known datums in North America are NAD-27 and NAD-83, which have subsets covering specific regions like Alaska, Canada, Mexico, and other regions and countries in North America. In Europe, OSGB-36 is well known in the United Kingdom, and ED-50 is commonly used in other European countries.

The optional Datum Pack includes over 230 additional datums, covering regions and countries on all continents around the world. You can browse this list by opening the Pro Compass preferences screen via the PREF button and tapping on the "Geodetic Datum..." button. You can purchase the Datum Pack, which includes all datums shown in the list (as well as any future additions), by selecting any non-default datum in the list. You will be prompted to complete a one-time in-app purchase through the iTunes App Store to install the Datum Pack feature. This purchase is transferable to all of your devices running Pro Compass under your iTunes account.

Once installed, you can select any datum that is part of the Datum Pack, and Pro Compass will use the datum to convert raw GPS data into position and altitude. Most regional datums have a limited range of applicability; if you are in a position outside of that range, the datum status indicator on the main screen (to the right of the position and altitude accuracy) will show "ERR". This doesn't necessarily mean that computed position and altitude are wrong, but it does suggest that the active datum is not going to provide accurate results, so another datum is likely more appropriate.

The Datum Pack has an architecture that will easily accept additional datums in future releases (at no extra charge). If you would like to use a datum that is not currently included, or have any other feedback on datums, please let us know.

Note: if you have a question/issue not addressed by the FAQ, please contact the developer.

First, try rebooting your device. If that doesn't solve the problem, delete the app and reinstall it. This is an App Store issue, and not specific to Pro Compass.

Pro Compass requires a device with built-in magnetometer (compass) hardware and iOS 11.4 or later. If your device does not meet these requirements, you cannot purchase or install Pro Compass.

Please check iOS System Settings App under "Privacy > Location Services" and make sure you are allowing Pro Compass to use location data. Many people turn this off without realizing it. Be aware that you need a clear line of sight to the sky to receive GPS location data, and a network connection is required for fast GPS refinement. Without a network connection, GPS location data is still available, but the initial location fix will take much longer (tens of seconds or even minutes). This behavior is characteristic of the device's location services implementation and not controlled by Pro Compass itself.

Only iPhones and iPads with cellular can display altitude. For these devices to receive proper altitude data from GPS, they must have a clear line of sight to four satellites in the sky. Altitude may not be available if you are indoors or if your view of the sky is obscured. In marginal cases, you may receive position data but no altitude.

If your compass-equipped device is not showing compass data, or the data is not updating, your device is probably being affected by electromagnetic interference. The magnetometer is susceptible to interference inside cars, near metal objects/structures, or near electronic equipment. Try moving to a different location, and wave the device in a figure eight motion to recalibrate the magnetometer.

Try running the inclinometer calibration (accessed via the app's preferences). Position the device on a flat, level, stable surface, and the calibration process will associate this with zero elevation and pitch.

The app's accuracy is limited by what the hardware can provide. For good GPS data, make sure you have a clear line of sight to the sky. For good compass data, be sure you are away from any sources of electromagnetic interference. Note that the device corrects altitude data based on a very simple model of the Earth's surface, so altitude is only approximate in most cases. This is an inherent limitation of the device and SDK.

Position coordinates can be displayed in several ways. The two options on the left of the "Position Format" control in preferences are for an absolute reference system given in degrees, with North latitude and East longitude taken as positive directions. The first option gives position in decimal degrees, while the second option gives position in degrees-minutes-seconds. The third option uses the Military Grid Reference System (MGRS), and the final options are standard and banded UTM.

The GPS and location hardware in all iOS devices (and most consumer GPS devices) defaults to the WGS-84 ellipsoid. Pro Compass 1.1 and later offer an optional Datum Pack that includes over 230 additional datums that can be used in the app.

First of all, make sure the real compass is not near your device, as it can interfere with the compass needle and throw it off. Then make sure you are comparing magnetic direction from the app so that it will be consistent with a real compass. Device compass accuracy is generally in the range of 2 to 10 degrees, but can be as poor as 20 or 30 degrees if there is electromagnetic interference.

Go into your device's settings, under "Location Services". Scroll to the bottom, and select "System Services". Make sure that the "Compass Calibration" option is turned on. This is required in order for Pro Compass to get magnetic declination information from GPS, which is used to compute a true direction. If you have this turned off, only magnetic direction can be shown in the app.

On a "direct read" compass, the needle tracks the north/south magnetic poles and the bearing is indicated by the north pointer on the needle. This convention requires that east and west be reversed for display/reading purposes. All direct read compasses use this convention, and most professionals are trained in it. The classic Brunton "Pocket Transit" is a direct-read compass, as is the well known US military "M2 Compass".

If you need assistance or have feedback, please contact:

dev@hunter.pairsite.com
Feature requests, comments, and suggestions are welcome.

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