Lateral deviation - Runway
Christian Reinecke
Chant, Adam
Chris,
To calculate lateral deviation from the runway centerline using DGPS position data in IADS, you will need to define the runway centerline and then use that definition to calculate the lateral deviation. Here's how you can approach this, combining information
from the sources:
- Define the Runway Centerline:
- Using Markers: You can use markers to define the runway centerline, especially if you're using an image like an airfield or satellite image that doesn't have lines of latitude and longitude.
o Create markers at each end of the runway.
o Use a program like Google Earth to get the exact latitude and longitude of the runway ends.
o Position the markers on the ends of the runway and enter the known lat/lon values for each marker.
- Using Georeferenced Maps: If you have a georeferenced map, you can use the map's coordinate system directly.
o Define the Latitude of Origin and Longitude of Origin which represent the center of the Lambert Conical Conformal projection on the map. This is essentially the horizontal and vertical center of the map.
o Define the 1st and 2nd Parallels, which are two latitude values that are closest to the top and bottom of the chart.
o Estimate the coordinates for the corners of your map.
- Calculate Lateral Deviation:
- Coordinate Transformation Functions: IADS includes functions for coordinate transformations that can be used to perform the necessary calculations.
o LLAtoECEF: Convert your DGPS latitude, longitude, and altitude to Earth-Centered, Earth-Fixed (ECEF) coordinates using the CoordinateTransformationFuncs.LLAtoECEF_X, CoordinateTransformationFuncs.LLAtoECEF_Y, and CoordinateTransformationFuncs.LLAtoECEF_Z functions.
o You will need to convert your latitude and longitude to decimal degrees, and altitude to meters.
o Define Centerline: Based on the runway end-point coordinates, calculate the coefficients of a line equation.
o Calculate Deviation: Calculate the lateral deviation by computing the shortest distance between the current ECEF position and the runway centerline vector you defined above. You can use a combination of functions such as CoordinateTransformationFuncs.ECEFLookAngles_Az , CoordinateTransformationFuncs.ECEFLookAngles_EL, and CoordinateTransformationFuncs.ECEFLookAngles_Range to determine the location of the aircraft in relation to the runway, then compute the lateral deviation. The TerrainFuncs also offer similar calculations.
o Great Circle Azimuth and Distance: You can use TerrainFuncs.GreatCircleAzimuth to get the azimuth of the runway and TerrainFuncs.GreatCircleHav or TerrainFuncs.VincentyInverse to get the distance to the runway centerline.
o Vincenty Direct: TerrainFuncs.VincentyDirectLat and TerrainFuncs.VincentyDirectLon can help calculate the coordinates of a point along the runway centerline based on starting point, azimuth, and distance.
- Derived Parameters: Create derived parameters in IADS to implement these calculations.
o Use the functions from CoordinateTransformationFuncs or TerrainFuncs as the Data Source Argument for these derived parameters.
o Ensure that the ParamType for the output parameter is set correctly (i.e., iadsFloatingPoint).
- Display and Verify:
- Cross Plot: Use a cross plot to show the lateral deviation over time, or to compare lateral deviation to another parameter.
o You can use the Cross Plot to clamp data to the min/max of the axes.
o You can also use the Cross Plot's envelope feature to track operating limits.
- Moving Map: You could display the aircraft's position and the runway centerline using a Moving Map display.
o Import overlay information using an external overlay text file to the MovingMapOverlays table in the Configuration Tool.
- Text Display: Use a text display to show the numerical value of the lateral deviation.
- Parameter Analysis Tool: Use the IADS Parameter Analysis Tool to debug the derived parameter to ensure your calculation is working correctly.
By following these steps, you should be able to accurately calculate and display the lateral deviation from the runway centerline using DGPS data in IADS.
Thank you,
Adam Chant
Project Engineer, IADS
Curtiss-Wright
190 Sierra Court A-3 Palmdale, CA 93550
T: 661.273.7003 x 2210
ach...@curtisswright.com
From: 'Christian Reinecke' via IADS <ia...@googlegroups.com>
Sent: Friday, January 24, 2025 11:12 AM
To: IADS <ia...@googlegroups.com>
Subject: [IADS] Lateral deviation - Runway [EXTERNAL]
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