Usage of the iHUD Multi Function Display (MFD)
iHUD depicts real-time visualization of attitude, attitude changes, heading, altitude, and velocity information in an aerospace inspired graphical display, known as Glass Cockpit (EFIS/AHRS). iHUD makes use of the internal 3-axes accelerometer sensors and the on-board GPS receiver of the genius iPhone 3G.
iHUD depicts an extraordinary graphic interface with a simulated horizon and a vehicle reference symbol, dynamic speed, altitude, and vertical velocity ribbons and digital display window, rotating compass card with compass bug, slip/skid ball, and an accelerometer (G-meter).
iHUD offers a fantastic way to teach, see, and learn EFIS and partially AHRS on-the-fly.
Important Note: An important limitation of this basic version of iHUD is that the horizon depends on the on-board accelerometers only. This means that the horizon does not display the earth horizon as a reference of a vehicle in an accelerated attitude. It will display the acceleration of the vehicle only. Therefore, never ever use iHUD in its present release for in-flight operations to visualize attitude. We are currently studying the possibility to mathematically model an algorithm to address this situation.
Note: Based on the fact that iHUD makes use of the accelerometer sensor and GPS receiver, expect higher drainage of the internal battery for extended use. We suggest that you plug the iPhone 3G into an external power source in your vehicle (cigarette lighter adapter).
Note: At startup of iHUD, data are gathered from the GPS for recalculation. Please be aware that up to 10 seconds, the displayed data might not be accurate until data smoothing delivers reliable display.
iHUD 2.0 main window
The new features are:
- Augmented reality (AR) with camera overlaid by the HUD spatial motion visualization (devices with camera only)
- iHUD spatial motion dispaly projection to windshield for night reflective vision
- Alternative use of onboard magnetic compass or GPS for heading information (for iPhone 3GS and newer), switchable.
- Dramatically improved speed dynamic display using the new capabilities in the CoreLocation framework.
- Sky color gradient provides a beautifully realistic sky.
- Minor adjustments and detailing
- A MODE button has been added for the three modes: EFIS - Reflective vision - Augmented Reality (AR)
- Double tapping in the center of the compass rose will toggle between the heading source, or selectable in SETTINGS (GPS/Compass option)
New additional view modes (toggle the MODE button for the different views)
Augmented Reality view (AR)
Use of the iPhone camera allows to simultaneously observe real-time visualization of attitude, attitude changes, heading, altitude, and velocity information (HUD) and the camera view.
If enabled, the on-board magnetic compass shows heading even when not in motion. Just turn with the iPhone 360º and you will see the change in heading.
You make take a snapshot any time by pressing the ''home' button and quickly press the on/off button of the iPhone.
In the picture you have a shot during a flight - cool!
Always check proper attitude calibration (CAL) for accurate visualization
The reflective view is used to project on a reflective surface at dark. Works best on a tinted windshield or tinted area of the windshield. Clear glass area might produce a double image.
Note that the status ribbon is kept in normal view for better manipulations.
Important: Before use, always check for proper attitude calibration (CAL) of the device position to be used for projection, otherwise attitude may not display correctly.
The picture above shows a typical iHUD screen while in operation with full signal.
Glass Cockpit visualization regions explained
|iHUD 2.0 utilizes the onboard magnetic compass feature as an alternative data input to the GPS heading information. Please note that the magnetic compass is only available on iPhone 3GS|
Both compass inputs can be selected on the fly by double tapping in the center of the compass card, or selected in the SETTINGS area (GPS/ Compass Options).
If the magnetic compass is selected, a white flag with the letter 'M' is displayed on the right side of the heading window.
The on-bored magnetic compass is highly susceptible to magnetic disturbances such as in a car or UFO. Calibration may be needed or, if calibration does not lead to good results, GPS compass will be needed (device must be in motion for GPS data!)
|The calibration procedure is the built-in routine on the iPhone 3GS. It is invoked when data are inconsistent. The heading window will be crossed and the HDG flag will turn red. If calibration is successful then the the HDG flag changes to green and the heading window displays the heading value.|
MENU strip with Buttons and Status
The screenshots below represent various stages from start-up, calibrations, settings, and operation.
|Start-up screen.||This is the WARNING screen, which you have to acknowledge.|
|After touching SETTINGS button, these are the available options.||iHUD 2.0 GPS/ Compass Options. ONly the iPhone 3GS features the on-board magnetic compass.|
|iHUD 2.0 INFO window with selection. Except for 'Warning', allother choices leave iHUD and invoke SAFARI web browser.||Slider for manual seletion of accelerometer smoothing parameter. Higher settings means stronger smoothing but also display lag. Optimize for your needs. 3GS best in upper range.|
|IMPORTANT: This calibration will correct for sensor offset values of the accelerometer data. Do it if in doubt!||After completion of the calibration, a sound alert!s you and it is shown on the screen. You are ready to use the iHUD.|
iHUD screen examples
|From SETTINGS you can access the user selectable display options. Input the value for the heading bug, or you can do it on- the-fly on the Glass Cockpit screen by touching the bug and moving it around the compass rose. Sample shows input.||From SETTINGS you can access the user unit selections as shown on the screen. Any combination above is possible.|
|Acquiring GPS signal. No GPS data for speed, heading, altitude, and vertical speed.||Selective GPS signal available, no altitude and vertical velocity yet.|
|Fully operational sample screen. Note: speed ribbon||High-speed low-pass and gentle vehicle pull-up|
Setup, Settings & Calibration
Initial Setup and Calibration
Before use, the iPhone or iPod Touch needs to be calibrated in two steps. First, any accelerometer offsets in the device need to be corrected. The accelerometer used in the iPhone and iPod touch typically has ± 0.04g to 0.06g of offset per axis from the factory. This can be corrected out by using the "Advanced Calibration" option in iHUD settings ‘Offset Calibration’, with the device placed face up on a flat level horizontal surface. Under normal circumstances, this particular calibration only needs to be performed once, but is recommended when in doubt.
Next, for operation the device needs to be placed in a vehicle and iHUD needs to be calibrated for position with the vehicle at rest and level. Position and mount the device always horizontally level (like wings level in an airplane). See example of the iPhone in a car with alignment arrow below. The display face can be at any tilt angle for best view, vertical ± any angle. Now use the CAL function on the main display (Glass Cockpit) and calibrate the pictorial horizon such that it is perfectly lined up with the reference target cross when the device is level.
Ready - go!
|iPhone with iHUD physical position requirements for accurate display.|
The device must be positioned along the lateral axes and perpendicular to the longitudinal axes. Any tilt angle is acceptable.
|iPhone with iHUD shows the striking similar display characteristics of an actual EFIS/AHRS display in a airplane (RV8, Larry O'Brien). Note the superb screen of the iPhone!|
Accelerometer sensor offset calibration
Before the first time usage for accurate readings, accelerometer sensor offset calibration is recommended. While operation iHUD, calibrate as needed for best accuracy. See initial setup and calibration for details.
iHUD offers standard USA and metric units. Under ‘Units’ select and combine frequently used units of your preference.
GPS speed display selection
iHUD allows you to select four speed ranges displayed in the speed ribbon as white/green, green, yellow, and red moving ribbons with white/green as the lowest. You find this under ‘Display Options’. This emulates speed indicator in airplanes. Fun!
Heading or Compass Bug
The Heading Bug or compass bug can be set to show the desired heading (track). On the EFIS/AHRS screen, touch the yellow big (double triangle) and drag it around the compass to set the desired heading. Alternatively, set the heading bug in the provided data field in SETTINGS under ‘Display Options’.
GPS options (release 1.1)
Since smooth graphics and realistic data of speed, heading, altitude, and vertical speed depends entirely on the accuracy of the GPS (or tower availability), we decided to implement a user selectable accuracy threshold in terms of horizontal error margin (feet, m).
This threshold simply rejects values that have greater error than the selected for the smoothing algorithm.
GPS satellites in line of sight and more than 3 satellites in view will give the best accuracy of approx. 60 feet on the iPhone. On the ground, this might not be achievable everywhere. We found that 600 feet to 800 feet threshold works quite well in most cases. If no GPS is available, then it is best to set the threshold to 'All'. We recommend to play with these settings.
Accelerometer smoothing (release 2.1)
Users can now set the smoothing value for display of the attitude (horizon) that fits best their needs. This is provided by a slider in the SETTINGS window. Higher value means more smoothing (less jitter) but also higher lag of the display. Users have to select the optimum setting according to their application. It also depends on the processor speed of the iDevice (3GS is faster than the 3G).
The iHUD is intended to for education, entertainment, and recreation use only. Please read warning information click here.
The iPhone 3G integrates a high performance AGPS (assisted GPS receiver) baseband processor and a low-noise GPS RF front end. It comes packed with new software features such as advanced multi-path mitigation that avoid large errors in urban environments caused by reflected signal in buildings and other structures. Data provided by the iPhone interface are coordinates of the position (longitude and latitude) each with a unique time stamp from the iPhone system clock. Displayed speed, heading, altitude, and vertical speed are significantly depending on accuracy of the position data form the GPS and the time stamp delivered by the iPhone. We observed that erratic date supplied by the interface are not uncommon. Therefore, you may observe variation on the graphical display of the parameter mentioned.
Note that for best GPS data signal, line of sight to the GPS satellites is required!
The accelerometer used in the iPhone and iPod touch typically has ± 0.04g to 0.06g of offset per axis from the factory. This can be corrected out by using the "Advanced Calibration" option in iHUD settings ‘Offset Calibration’.
Attitude indication (AHRS)
The AHRS in the present form of iHUD has an important limitation. Since we have only the three-axes accelerometer information for measuring loads acting on the iPhone and not angular rate of changes (like a stabilized gyro) means that the horizon display depends solely on the on-board accelerometers. Thus the horizon can not display the earth horizon as a reference for a vehicle in an accelerated motion (iPhone device).