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iHUD

iHUD basic


Glass cockpit iHUD - EFIS AHRS motion visualization on the iPhone - iHUD app suite

iHUD suite - Your mobile spatial motion visualization on the iPhone / iPad


iHUD is an app that turns the iPhone (3G and higher), iPhone 4, iPad 3G, and - with limited features the iPod touch 2nd generation and higher *) - into an aerospace-inspired mobile Glass Cockpit.  iHUD derives its name from Head-Up Display, which depicts motion and flight-related pertinent guidance information and data for optimal situational awareness.

A Glass Cockpit usually features an AHRS and an EFIS for visualization of position, attitude, attitude changes, track and acceleration of the vehicle in space and time.  AHRS means Attitude and Heading Reference System.   AHRS delivers primary spatial motion information to the pilot.  EFIS means Electronic Flight Information System, which displays the obtained information in the Glass Cockpit, also known as a Multi Function Display (MFD).

In aerospace, EFIS/AHRS is a cost-effective replacement for traditional vacuum-powered mechanical gyros (steam gauges! Just kidding). Without mechanical gyros, no maintenance is required, and the resulting system is much lighter and way more powerful and very reliable. In addition to the primary flight information, power plant sensor data, and maps for guidance (moving map) may also be displayed. There are many Glass Cockpit variants - from very simple (starting price of ± $2000.-) to amazingly complex (> $100,000.-) - but they have in common all the basic information of attitude, attitude changes, heading, speed, vertical speed, and acceleration.  Imagine all this information is simulated by iHUD, made possible by the iPhone’s on-board accelerometer and GPS sensors.

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 user selectable heading bug, slip/skid ball, and an accelerometer (G-meter). iHUD is a fun experience for everybody who likes to see motion and forces acting on the vehicle they are riding on. Try it on a giant roller coaster (just don't let go of the iPhone!).

iHUD offers a fantastic way to teach, see, and learn EFIS and partially AHRS functionality in the classroom on-the-fly.

*) The iPod touch has no on-board GPS receiver, therefore only accelerometer based information (attitude with pitch and roll, and G-load) is operative.

Glass Cosckpit iHUD - EFIS artificial horizon motion visualization in operation

PILOTS!

iHUD Remote for pilots:

iHUD Remote on the App Store

a portable EFIS display linked by Wi-Fi to external AHRS modules

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HUD operating manual

Warnings & Limitations:

Please use the iHUD responsibly. iHUD is not intended for steering airplanes, helicopters, boats, motorcycles, and other powered vehicles, and UFO's. It is for entertainment and educational purposes only

A limitation of this basic iHUD is that the horizon is evaluated by the on-board accelerometers. This means that the horizon cannot display the earth horizon as a reference of a vehicle. It will display the acceleration of the vehicle only and the forces acting on the vehicle. Therefore, never ever use this version of iHUD for in-flight operations to visualize attitude (artificial horizon).



GETTING YOU STARTED QUICKLY

-> Start iHUD - Fig.16

-> Main iHUD window (EFIS), Fig.1
- Check for green GPS status indicator (make sure Location Services are turned on)

->
Main iHUD display (EFIS) features and actions
- Speed ribbon, altitude, vertical speed, heading, slip/skid, g-load, Horizon
- Double click on the compass rose for toggling in sequence compass source (GPS or magnetometer)
- Turquoise diamond shows magnetic declination based on GPS location
- Day/night button (left upper window corner) will a red filter (dimmable)
- Move the heading bug, yellow double triangle on the compass (with finger, hold and move around)

-> Make yourself familiar with all iHUD features
- Check MODE (Main EFIS, Reflective view, Augmented Reality view - AR), Fig.1
- Check SETTINGS (All user selectable Settings in various pages), Fig.2
- Check INFO (Warning screen, Quick Start Briefing, and more), Fig.3


TERMINOLOGY

HUD Head Up Display
EFIS Electronic Flight Information System
MFD Multi Function Display
AR Augmented Reality (iHUD display with camera view overlay)
M Magnetic heading Magnetometer or GPS)
T True or geographic heading (Magnetometer or GPS)
IAS Indicated Air Speed

DISPLAY & OPERATION - Fig.1

-> iHUD main EFIS Screen parameter presentation

-> Simulated Pitch and bank from the onboard accelerometers.

-> Heading (M or T) on a compass rose with user selectable heading bug.

-> Toggle (four states) between GPS true heading (T GPS) and GPS magnetic heading (M GPS), or magnetometer
magnetic heading (M Magnetometer) and magnetometer true heading (T Magnetometer).

-> Select heading source by double tapping on the compass rose for sequencing the four states (M GPS, T GPS, M Magnetometer,
T Magnetometer).

-> Calculation between true (geographic) and magnetic heading is based on the magnetic declination algorithm of the World
Magnetic Model (WMM) and is automatic, no user interaction is needed.
-> A turquoise colored diamond icon on the compass rose
indicates the declination value calculated from the current iDevice GPS
location, altitude, and date, continuously updated.

-> Airspeed (AD) or GPS speed on a moving Speed Ribbon with a digital speed window.

-> GPS altitude shown by a moving Altitude Ribbon.

-> Vertical Speed (VS) is shown with a moving VS-indicator window (GPS).

-> G-load positive or negative with respect to gravity (accelerometer based).

-> Ball shows slip/skid, cornering g-load for cars (accelerometer based).

->Day/Night button for night dimming the EFIS display (not AR or Reflective view).

-> iHUD Status Indicators show:
SPD (Speed), ALT (Altitude), HDG (Heading).
green- signal available and usable
yellow- signal strength marginal
red- signal/sensor not available or not responding (triggers red crosses where applicable)


MODE button

Toggle between:
->EFIS view (standard) - Fig.1
-> Augmented reality with camera (AR) overlaid with iHUD information - Fig.4
-> iHUD reflective projection to windshield for night operation as HUD (reverse iHUD screen) - Fig.5


INFO button

Link to:
-> Warning screen - Fig.17
-> Quick Start Briefing - Fig.6

-> Terms of Use / EULA
-> iHUD Web Site (Internet needed)


SETTINGS buttonFig.2
Note:
From any nested settings menu, you can backtrack (back button) or directly return to the main iHUD Remote screen (blue iHUD display button)

Display Options - Fig.2
Device Display Options - Fig.7
-> Device Orientation -> Landscape Left or Right, default is ‘Right’
-> Day/Night Dimming -> Slider allows lighter or darker, default 35%

Data Display Settings - Fig.8
-> Units - Fig.9
Speed, Altitude, Vertical Rate -> in aviation common units
-> V-Speeds - Fig.10
Select speeds for:  VS0  VFE   VS1   VNO   VNE in units selected
-> Declination - Fig.11
Declination Info -> Value (N, E) based on GPS location & altitude       
-> Declination Calculator - Fig.12
Offline magnetic declination calculator we used for testing, it may be useful

GPS / Compass Options - Fig.13
-> T GPS  or  M GPS  or  M Magnetometer  or  T Magnetometer selection
-> Compass Heading Bug -> set desired value
-> GPS Horizontal Accuracy Threshold -> Slider (default set to high)

Accelerometer Smoothing - Fig.14
-> Slider provides low to high smoothing value, default setting at about 70%

Offset Calibration - Fig.15
-> Initial iDevice accelerometer offset evaluation procedure. Needs to be done only once, or as needed

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START & USAGE

Initialization & Calibration

Before the first time use and later for accurate readings, the iDevice accelerometer needs to be calibrated in two steps. First, any accelerometer offsets in the device need to be corrected. The accelerometer used in the iPhone, iPod touch, and iPad typically has ± 0.04 g to 0.06 g 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). The display face can be any angle for best display, vertical, ± any angle. Now use the CAL function on the main display (Glass Cockpit) and calibrate the horizon such that it is perfectly lined up with the reference target cross when the device is level.

Ready - go!  


positionong the iPhonw with iHUD
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.
Positioning the iPhone with iHUD in airplanes
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!




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Usage Briefing

CAL

The CAL button is used to calibrate the Glass Cockpit for level conditions in any position, can be applied any time while using iHUD (see step 2 above).

MODE
Toggle between EFIS view (standard), iHUD reflective projection to windshield for night operations (inverse), and Augmented reality with camera (AR) overlaid with iHUD information. Note: Using screen shots with the AR options allow to record certain motion situations.

SETTINGS

Allows various user selectable inputs, setup, and offset calibration Status lights (3) - show conditions of GPS signal (speed, altitude, heading) with colors (red –yellow- green)


INFO

Link to the Warning screen, Information Page, EULA, and i-HUD.com web site.



Notes on each Settings option:

Units

HUD Remote offers standard USA and metric units.  Under ‘Units’ select and combine frequently used units of your preference. Under ‘Data Display Settings’.

V-Speeds

iHUD Remote allows you to select the most common V-Speed ranges displayed in the speed ribbon as white/green, green, yellow, and red line moving ribbons. 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 ‘‘Data Display Settings’. This emulates speed indicator in airplanes. By use of the most common V-Speeds, VS0  VFE   VS1   VNO   VNE in units selected.  Under ‘Data Display Settings’.

Declination

Declination is evaluated on the basis of the iDevice GPS location and altitude and is constantly updated while in motion. Please check that Location Services is set to ON, and also set to ON for iHUD Remote. Declination is automatically calculated based on the WMM (World Magnetic Model) and is applicable worldwide. The declination values can be positive (E) or negative (W). Declination is displayed on the compass rose represented by a turquoise colored diamond. Under Data Display Settings’.

Display Compass Heading

Select compass heading source by using provided desired button. Choose between T GPS  or  M GPS  or  M Magnetometer  or T Magnetometer. Note that GPS delivers geographic (true, T) headings, and the iDevice magnetic compass delivers magnetic headings (M). To be found under ‘GPS / Compass’ Options.


GPS Horizontal Accuracy Threshold

Since smooth graphics and realistic data of speed, heading, altitude, and vertical speed depend 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 50 feet to 500 feet threshold works quite well in most cases. For later iDevice models, higher accuracy seems better. If no GPS sensor is available, then it is best to set the threshold to 'All'. We recommend playing with these settings.

You may toggle between the two sources by double tapping on the center of the compass rose. A flag (M) appears on the right of the heading window if the magnetic compass is activated. GPS input is only meaningful if the device is in motion, the magnetic compass is very susceptible to disturbances form any metal and electronics. If the magnetic compass is erratic, the heading window is crossed and the heading indicator on the status line changes to red. Built-in magnetometer calibration is provided.  To be found under ‘GPS / Compass’ Options.


Accelerometer Smoothing

Users can set the smoothing value for display of the attitude (horizon) that fits best their needs. A slider in SETTINGS provides this feature. 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, iPhone 4S is faster than iPhone 4).


Offset Calibration

Before the first time use and later for accurate readings, the iDevice accelerometer needs to be calibrated in two steps. First, any accelerometer offsets in the device need to be corrected. The accelerometer used in the iPhone, iPod touch, and iPad typically has ± 0.04 g to 0.06 g of offset per axis from the factory. Detailed instruction on the calibration page. To be found under ‘GPS / Compass’ Options.



GPS accuracy threshold and GPS remarks

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 playing with these settings, especially for older Devices.

GPS is only meaningful, if the device is in motion, the magnetic compass is very susceptible to disturbances form any metal and electronics. If the magnetic compass is erratic, the heading window is crossed and the heading indicator on the status line changes to red. Built-in magnetometer calibration is provided.

iHUD Remote offers the useful feature for selecting at any time GPS derived parameters  in the case that AHRS connection is not available or temporarily lost by using the iDevice internal GPS receiver for speed, altitude, heading, and vertical speed.

GPS reception needs GPS satellites in line of sight and more than 4 satellites (more is better) in view will give the best accuracy of < 60 feet on the iDevice. On the ground, this might not be achievable everywhere. We found that 60 feet to 600 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 playing with these settings.

Device Orientation

The iDevice can only be used in a preselected orientation. If the iDevice would automatically flip the orientation, the data used for iHUD from the accelerometers would be undefined and in a complete roll or pitch situation (loop, roll) the display would show a wrong attitude.

We have selected landscape right (home button is on the right side) as the default orientation (landscape right) and have added the orientation (landscape left), switchable by the user. This can be changed in ‘Data Display Settings’.

Day/Night Dimming

The Day/Night button  on the main window has a preset dimming value. This can be changed in ‘Device Settings’ by use of a slider (lighter <--> darker). A red filter is applied as the basis for dimming, Fig.15.



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Limitations

GPS
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:For best GPS data signal, line of sight to the GPS satellites is required!

Accelerometer sensors
The accelerometer used in the iPhone and iPod touch typically has ± 0.04 g to 0.06 g 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 (artificial horizon)
The 'artificial horizon' 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). It will display the acceleration forces acting on the vehicle only. Therefore, never ever use this version of iHUD for in-flight operations to visualize attitude (except pitch and bank in a un-accelerated vehicle). We are currently studying the possibility to mathematically model an algorithm to address this situation.

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Knowledge base

Explanations of terms:

A Glass Cockpit usually features an AHRS and an EFIS for visualization of position, attitude, attitude changes, track and acceleration of the vehicle in space and time.  AHRS means Attitude and Heading Reference System.   AHRS delivers primary flight information to the pilot.  EFIS means Electronic Flight Information System, which displays the obtained information in the Glass Cockpit, also known as a Multi Function Display (MFD).

Attitude and Heading Reference Systems or better known as Attitude Heading Reference System (AHRS) are 3-axis sensors that provide heading, attitude and yaw information for aircraft. AHRS are designed to replace traditional mechanical gyroscopic flight instruments and provide superior reliability and accuracy.

AHRS consist of either solid-state or MEMS gyroscopes, accelerometers and magnetometers on all three axes. Some AHRS use GPS receivers to improve long-term stability of the gyroscopes. A Kalman filter is typically used to compute the solution from these multiple sources. AHRS differ from traditional inertial navigation systems by using magnetometer and/or GPS data to correct the raw gyroscopic data.

AHRS have proven themselves to be highly reliable and are in common use in commercial and business aircraft. Recent advances in MEMS manufacturing have brought the price of FAA certified AHRS down to below $15,000. AHRS are typically integrated into Electronic Flight Information Systems (EFIS), which are the central part of so-called glass cockpits. AHRS are often combined with air data computers to form an "air data, attitude and heading reference systems" (ADAHRS), which provide additional information such as airspeed, altitude and outside air temperature.

The EFIS/AHRS is a cost-effective replacement for traditional vacuum-powered mechanical gyros (steam gauges! Just kidding). Without mechanical gyros, no maintenance is required, and the resulting system is much lighter and way more powerful and very reliable. In addition to the primary flight information, power plant sensor data, and maps for guidance (moving map) may also be displayed.

In Aerospace, there are many Glass Cockpit variants - from very simple (starting price of ± $2000.-) to amazingly complex (> $100,000.-) - but they have in common all the basic information of attitude, attitude changes, heading, speed, vertical speed, and acceleration.

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Glass cockpit iHUD - EFIS AHRS motion visualization on the iPhone

Apple, the Apple logo, iPod, iPhone, and iTunes are trademarks of Apple Inc., registered in the U.S. and other countries.
iPhone is a trademark of Apple Inc
.

For more information contact AVI by e-mail



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AVI
Aero Visions Intl. Inc., 312 W Fourth Street, Carson City, NV 89703, USA
Aero Visions International Inc iPhone app developments

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