GPS Approach App

GPS based CDI, HSI and 2x2D Visualization for ILS and self defined Approaches

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This application is not certified for flight guidance!

GPS data accuracy is limited due to the device capabilities!

DO NOT USE AS SINGLE SOURCE OF GUIDANCE!

Any liability of the developper is excluded!

Concept

This App provides a guidance tool to train Approaches in General Aviation Airplanes or for Flight Simulators.

Approaches

You can creat your own approaches, with touch down area, elevation, bearing and glide path angle.
This enables you:

Visualization

For visualization while flying the approach you can use the aviation standards HSI and CDI but also a very useful 2x2D Visualization with a lot of handy features. Check this Out!!

Toggle between the visualizations by tapping the top area of the HSI, CDI or 2x2D view.

DME

At the bottom of the visualisation Page you find two also two DMEs which gives you the Distance to the selected DME (it shows the DME distance as 'slant range' and it is calculated trigonometrically upon the aircraft altitude above the DME as well as the ground distance)

Android GPS altitude issues - Geoid Correction

The Android API has some issues with the implementation of the GPS altitude.
On some devices the altitude provided by the device is only the height above the WGS84 ellipsoid and not corrected by the Geoid Height and therefore don't provide the right altitude above the main sea level.
So check this for your device!!!
If the displayed altitude is not correct, check the Geoid Height of the Approach you want to fly and insert and save this correction in m(meter) under the settings.
For Geoid Height calculation you can use e.g. the UNAVCO website
In Central Europe the correction is typically between 40m and 55m.

GPS altitude Errors

Be aware that the GPS altitude measurement of a smart phone is typically less reliable than the horizontal position, because it needs more Satellites to calculate.
Especially in Aircraft Cockpits the GPS Signal might not be perfect.
Therefore cross check the altitude with the barometric altitude and add some margin.
It might also be a good idea to use an external GPS Source with better reception.


Use with Flight Simulators

You can use the app also with a flight simulator like X-Plane. You only have to use the GPS output of X-Plane for your GPS Source. The App "X-Plane to GPS" is a great tool for this. You should set the Geoid Correction to 0 because X-Plane provides the right altitude already.

HSI

Typical "Glas" HSI

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HSI

This is a typical "Glas"-Type HSI

The HSI Page displays a rotating compass card in a heading-up orientation.
Letters indicate the cardinal points and numeric labels occur every 30°. Major tick marks are at 10° intervals and minor tick marks at 5° intervals.
The HSI also presents course deviation
(in Approach Mode 1° per Dot and Full scale deflection is 2.5°)
The following information is presented as Text:
Distance to Waypoint (Threshold)
GPS Groundspeed
Course of the course line
GPS Altitude
Target Vertical Speed (to follow Glide Path)

Vertical Deviation (Glideslope) Indicator

The Vertical Deviation (Glideslope) Indicator appears to the right of the compass rose. A magenta diamond acts as the VDI, like a glideslope needle on a conventional indicator. Glidepath Deviation is shown as 0.28° per dot and Full scale deflection is 0.7°

CDI

Typical old fashion CDI

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CDI

This is a typical analogue-Type CDI

The CDI Page displays a rotating compass card in a course-up orientation.
The two needles show the lateral and glideslope deviation angle.
The lateral deflection is shown in Approach Mode as 0.5° per Dot and Full scale deflection is 2.5°
The Vertical Deviation (Glideslope) deflection is shown as 0.14° per dot and Full scale deflection is 0.7°

2x2D

The 2x2D is a special Visualization

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2x2D View

This is special visualization, very helpful and with a lot of features

Top 2D View: Vertical Deviation (Glideslope) Visualization

This displays a side view, where you see the target Glideslope and the aircraft in relation to it.
The horizontal scale is depending on the zoom mode (automatic or fixed distance to threshold). In the top bar you see on the left side the threshold of the approach (0NM) and the threshold altitude in ft. On the right side you see the actual scale in NM and altitude of the Glideslope at this distance. A light blue bar visualizes the actual scale (4NM: long bar, 11NM mid bar, 20NM small bar).
Below the aircraft at the bottom you see the actual distance of the aircraft to the threshold (moving with the aircraft).
Above the aircraft in the second top bar you see a moving indication of the target altitude, which the aircraft should have, if it were on the Glideslope (cyan) and the actual altitude (in green near the target altitude, otherwise in some red colors ). On the left side the following information is presented as Text:

  • Target Vertical Speed(cyan): Target Vertical Speed for the Glideslope at the actual Ground Speed.

Bottom 2D View: Horizontal Deviation (Localizer) Visualization

This displays a top view, where you see the target approach course and the aircraft in relation to it.
On the top you see the approach course and the actual offset of this 2D view
On the bottom you see the counter approach course and the scale distance to the threshold
This top view have to modes (you can toggle between them by tapping this top view area):

  • Linear View: you see the full area from threshold (0NM) to the scale distance (4NM, 11Nm or 20NM).
    x,y Axis are equally scaled.
  • Dynamic Dist Scale: the area is a 4NMx2NM rectangle detail. x,y Axis are equally scaled. The Center of this detail rectangle is the aircraft. To visualize the aircraft position in relation to the threshold, the center of the 4NMx2NM rectangle is moving with the aircraft to the top of the view
    It is hard to describe-try it!
    But it helps to use the turn guidance(see below) if you are turning to final in 10NM distance.

If scale permits in front of the Aircraft a Turn Guidance Line (yellow) is depicted. The end of the line indicates where the aircraft would reach the final approach course if a standard rate turn with the actual ground speed would be executed now. So, if you want to perfectly align with the final course, just start your turn, when the yellow line reaches the magenta course line.

On the left side the following information is presented as Text:
  • Actual Ground Speed(magenta )

Load, Add, Edit

Load Approaches and DMEs

Approaches

You change Approaches by tapping the Approach Button.
In the appearing List you can search an approach and select it by short tapping on the approach item.
By long taping an Item you can edit it
You also can add a new Item (it is prefilled with some data).

Import/Export

In the Settings Menu you can Import and Export Approaches via a semicolon separated text file to the app directory (normally found under Android/data/de.yconsult.GPSApprApp/files/)
By hitting the Import button it will delete the Approaches stored in the app and replace it by the approaches defined in the ApprData.txt file.
By hitting the Export button it will export all Approaches stored in the app to the ApprDataOut.txt file.

The line structure in the file should be as followed:
EDDW;Bremen;RWY 09;53.046574;8.774452;13;87.84;3.3
Where the Items are:
ICEO Identifier;Description;Runway;latitude;longitude;altitude in ft;runway true bearing;glideslope angle
The last line should be followed by a new line.

DMEs

You change Approaches by tapping the Approach Button.
In the appearing List you can search an approach and select it by short tapping on the approach item.

Import

In the Settings Menu you can Import DMEs via a semicolon separated text file to the app directory (normaly found under Android/data/de.yconsult.GPSApprApp/files/)
By hitting the Import button it will delete the DMEs stored in the app and replace it by the DMEs defined in the DMEData.txt file.

The line structure in the file should be as followed:
AGD;DME;ED;Altenburg DME;50.98277778;12.51222222;0;115.3
Where the Items are:
ICEO Identifier;DME;Country;Name;latitude;longitude;altitude in ft;frequency
The last line should be followed by a new line.

Generate

Generate Approaches

To generate an Approach Google Earth is good tool.
In Google Earth use the ruler and move to the threshold you want to generate a Approach for.
You see on the bottom right corner the latitude, longitude and altitude for the selected point, which you can use for the approach app.
Now use the ruler to set a second point on the counter threshold.
In the ruler window you can now read the exact heading for your approach.
For the glideslope you have to figure out what is the best for your approach. The standard ILS Approach is 3°. For a VFR field 4° might be more convenient.