NewGamePhysics.Physics.GravityMarsMroModel Class Reference

Model of earth's gravity g based on Mars Reonnaissance Orbiter (MRO) measurements and a higher-order gravity anomaly expansion model represented by a gridded map. Loader only supports GGMRO files. More...

List of all members.

Public Member Functions
	GravityMarsMroModel ()
	Constructs an uninitialized gravity mars object.
	GravityMarsMroModel (string mapFilename)
	Constructs a gravity mars object and initializes it by loading a anomaly map.
double	Calculate (double lat, double lon, double h)
	Calculate the acceleration g from the normal gravity and anomaly map of Mars at the surface. (height is ignored) Requires a mro map file to be loaded.
void	LoadAnomalyMap (string mapFilename)
	Load the GGMRO anomaly map file.
void	UnloadAnomalyMap ()
	Dispose of the current anomaly map.
Public Attributes
const double	Gal = 0.01
	Unit of acceleration, name: Galileo, 1cm/sec^2.
const double	G = 6.67428E-11
	Gravitational Constant (m^3 kb^-1 s^-2).
const double	GM = 42828.35796
	Mars Gravity Constant (G * M) in km^3/s^-2 Reference: ggmro model parameter file.
const double	R = 3397.0
	Mars Equatorial Radius in km. Reference: ggmro model parameter file.
const double	omega = 7.088218081e-5
	Mars's rotational speed in rad/s^-1. Reference: ggmro model parameter file.

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Detailed Description

Model of earth's gravity g based on Mars Reonnaissance Orbiter (MRO) measurements and a higher-order gravity anomaly expansion model represented by a gridded map. Loader only supports GGMRO files.

Definition at line 20 of file GravityMarsMroModel.cs.

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Constructor & Destructor Documentation

NewGamePhysics.Physics.GravityMarsMroModel.GravityMarsMroModel

(

)

Constructs an uninitialized gravity mars object.

Definition at line 79 of file GravityMarsMroModel.cs.

        {
        }

NewGamePhysics.Physics.GravityMarsMroModel.GravityMarsMroModel

(

string

mapFilename

)

Constructs a gravity mars object and initializes it by loading a anomaly map.

Parameters:

modelFilename

The anomaly map file to load.

Definition at line 88 of file GravityMarsMroModel.cs.

        {
            this.LoadAnomalyMap(mapFilename);
        }

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Member Function Documentation

double NewGamePhysics.Physics.GravityMarsMroModel.Calculate	(	double	lat,
		double	lon,
		double	h
	)

Calculate the acceleration g from the normal gravity and anomaly map of Mars at the surface. (height is ignored) Requires a mro map file to be loaded.

Parameters:

	lat	Latitude (deg) in the range [-90,90]
	lon	Longitude (deg) in the range [0,360]
	h	Height (m) above sealevel in the range [0,100000].

Returns:

Acceleration g.

Definition at line 102 of file GravityMarsMroModel.cs.

        {
            if (null == this.map)
            {
                throw new ApplicationException(
                    "Anomaly map not initialized. Load one first.");
            }

            if ((lat < -90.0) || (lat > 90.0))
            {
                throw new ArgumentOutOfRangeException("lat");
            }

            if ((lon < 0.0) || (lon > 360.0))
            {
                throw new ArgumentOutOfRangeException("lon");
            }

            if ((h < 0.0) || (h > 100000.0))
            {
                throw new ArgumentOutOfRangeException("h");
            }

            // Calculate index position
            int intLat = (int)Math.Truncate(lat);
            int intLon = (int)Math.Truncate(lon);

            // Create bicubic interpolator matrix
            double[,] G = new double[4, 4];
            for (int i = -1; i <= 2; i++)
            {
                for (int j = -1; j <= 2; j++)
                {
                    int indexLat = (LatWrap(intLat + i) - LatMin) % 180;
                    int indexLon = (LonWrap(intLon + j) - LonMin) % 360;
                    G[i + 1, j + 1] = map[indexLat, indexLon];
                }
            }

            // Interpolate over grid
            Bicubic bicubic = new Bicubic(G);
            double x = Math.Abs(lat - (double)intLat);
            double y = lon - (double)intLon;
            double g = bicubic.Calc(x, y);

            // Scale from mgal units
            // One milligal equals 0.01 mm/s/s.
            g *= 1e-5;

            // Add normal gravity
            double g0 = GravityMarsNormalModel.Calculate(lat);
            g += g0;

            return g;
        }

void NewGamePhysics.Physics.GravityMarsMroModel.LoadAnomalyMap

(

string

mapFilename

)

Load the GGMRO anomaly map file.

Parameters:

filename

The mro anomaly map file to load.

Definition at line 162 of file GravityMarsMroModel.cs.

        {
            // Load binary data
            FileStream fileStream = new FileStream(mapFilename, FileMode.Open, FileAccess.Read);
            BinaryReader binaryReader = new BinaryReader(fileStream);
            long totalBytes = new FileInfo(mapFilename).Length;
            byte[] byteArray = binaryReader.ReadBytes((Int32)totalBytes);
            binaryReader.Close();
            fileStream.Close(); 
            
            // GGMRO Image format
            // LINES                      = 180
            // LINE_SAMPLES               = 360
            // SAMPLE_TYPE                = IEEE_REAL
            // SAMPLE_BITS                = 64
            this.map = new double[180, 360];
            int startIndex = 0;
            byte[] tempArray = new byte[8];
            for (int lat = 0; lat < 180; lat++)
            {
                for (int lon = 0; lon < 360; lon++)
                {
                    // Get sample
                    // See: http://pds.jpl.nasa.gov/documents/sr/Chapter03.pdf
                    // and http://pds.jpl.nasa.gov/documents/sr/stdref2003/AppendixC.pdf
                    double sample;
                    if (BitConverter.IsLittleEndian)
                    {
                        for (int i = 0; i < 8; i++)
                        {
                            tempArray[7 - i] = byteArray[startIndex + i];
                        }

                        sample = BitConverter.ToDouble(tempArray, 0);
                    }
                    else
                    {
                        sample = BitConverter.ToDouble(byteArray, startIndex);
                    }

                    // Data format
                    // OFFSET                     = 0.0E+00
                    // SCALING_FACTOR             = 1.0E+00
                    // The values can be obtained by multiplying the sample in
                    // the map by SCALING_FACTOR and then adding OFFSET.  
                    double value = (1.0 * sample + 0.0);
                    this.map[lat, lon] = value ;

                    // Update source index
                    startIndex += (64 / 8);
                }
            }
        }

void NewGamePhysics.Physics.GravityMarsMroModel.UnloadAnomalyMap

(

)

Dispose of the current anomaly map.

Definition at line 219 of file GravityMarsMroModel.cs.

        {
            this.map = null;
        }

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Member Data Documentation

const double NewGamePhysics.Physics.GravityMarsMroModel.G = 6.67428E-11

Gravitational Constant (m^3 kb^-1 s^-2).

Definition at line 50 of file GravityMarsMroModel.cs.

const double NewGamePhysics.Physics.GravityMarsMroModel.Gal = 0.01

Unit of acceleration, name: Galileo, 1cm/sec^2.

Definition at line 45 of file GravityMarsMroModel.cs.

const double NewGamePhysics.Physics.GravityMarsMroModel.GM = 42828.35796

Mars Gravity Constant (G * M) in km^3/s^-2 Reference: ggmro model parameter file.

Definition at line 56 of file GravityMarsMroModel.cs.

const double NewGamePhysics.Physics.GravityMarsMroModel.omega = 7.088218081e-5

Mars's rotational speed in rad/s^-1. Reference: ggmro model parameter file.

Definition at line 68 of file GravityMarsMroModel.cs.

const double NewGamePhysics.Physics.GravityMarsMroModel.R = 3397.0

Mars Equatorial Radius in km. Reference: ggmro model parameter file.

Definition at line 62 of file GravityMarsMroModel.cs.

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The documentation for this class was generated from the following file:

• C:/Users/Andreas Schiffler/Desktop/SVN/NewGamePhysics/NewGamePhysics/Physics/GravityMarsMroModel.cs