NewGamePhysics.Physics.GravityEarthGfcGrid Class Reference

Grid interpolator of earths gravity based on data from the International Center for Global Earth Models (ICGEM). Reference: http://icgem.gfz-potsdam.de/ICGEM/ICGEM.html. More...

List of all members.

Public Member Functions
	GravityEarthGfcGrid ()
	Constructs an uninitialized gravity earth object.
	GravityEarthGfcGrid (string gridFilename)
	Constructs a gravity earth object and initializes it by loading a model.
double	Calculate (double lat, double lon, double h)
	Calculate the acceleration g from grid using bicubic interpolation. Requires a map file to be loaded.
void	LoadGravityMap (string gridFilename)
	Populate the gravity value map from an external file. Assumes the grid is in .gdf format from over the value range lat [-90,90] and long [0,360] in one degree steps.
void	UnloadGravityMap ()
	Dispose of the current gravity map.
Properties
int	Size [get]
	Gets the number of gridpoints loaded.

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Detailed Description

Grid interpolator of earths gravity based on data from the International Center for Global Earth Models (ICGEM). Reference: http://icgem.gfz-potsdam.de/ICGEM/ICGEM.html.

Definition at line 19 of file GravityEarthGfcGrid.cs.

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Constructor & Destructor Documentation

NewGamePhysics.Physics.GravityEarthGfcGrid.GravityEarthGfcGrid

(

)

Constructs an uninitialized gravity earth object.

Definition at line 55 of file GravityEarthGfcGrid.cs.

        {
        }

NewGamePhysics.Physics.GravityEarthGfcGrid.GravityEarthGfcGrid

(

string

gridFilename

)

Constructs a gravity earth object and initializes it by loading a model.

Parameters:

modelFilename

The gdf grid file to load.

Definition at line 64 of file GravityEarthGfcGrid.cs.

        {
            this.LoadGravityMap(gridFilename);
        }

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Member Function Documentation

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

Calculate the acceleration g from grid using bicubic interpolation. Requires a 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 86 of file GravityEarthGfcGrid.cs.

        {
            if (null == this.grid)
            {
                throw new ApplicationException(
                    "Gravity 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;
                    int indexLon = LonWrap(intLon + j) - LonMin;                    
                    G[i+1,j+1] = grid[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
            g *= 1e-5;

            // Adjust for elevation
            g -= (3.086e-6 * h);

            return g;
        }

void NewGamePhysics.Physics.GravityEarthGfcGrid.LoadGravityMap

(

string

gridFilename

)

Populate the gravity value map from an external file. Assumes the grid is in .gdf format from over the value range lat [-90,90] and long [0,360] in one degree steps.

Parameters:

gridFilename

The grid file to load.

Definition at line 146 of file GravityEarthGfcGrid.cs.

        {
            // Create new grid 
            size = 0;
            grid = new double[(LatMax - LatMin + 1), (LonMax - LonMin + 1)];

            // Prep data reader
            Scanf scanf = new Scanf();
            FileStream fileStream = null;
            StreamReader streamReader = null;
            try
            {
                fileStream = new FileStream(gridFilename, FileMode.Open);
                streamReader = new StreamReader(fileStream);
                string line;
                while ((line = streamReader.ReadLine()) != null)
                {
                    object[] o = scanf.Scan(line, " %lf %lf %lf");
                    if ((null != o) && (o.Length == 3))
                    {
                        int lon = (int)Math.Truncate((double)o[0]);
                        int lat = (int)Math.Truncate((double)o[1]);
                        double g = (double)o[2];

                        // Check if the grid indices are in the right range
                        if ((lat < LatMin) || (lat > LatMax) || (lon < LonMin) || (lon > LonMax))
                        {
                            throw new Exception("Invalid data: " + line); 
                        }

                        int latIndex = lat - LatMin;
                        int lonIndex = lon - LonMin;

                        // Make sure we don't double write a grid point 
                        if (grid[latIndex, lonIndex] != 0.0)
                        {
                            throw new Exception("Double grid value: " + line);
                        }

                        // Store value in grid                        
                        grid[latIndex, lonIndex] = g;
                        size++;
                    }
                }
            }
            finally
            {
                if (null != streamReader)
                {
                    streamReader.Close();
                }
                if (null != fileStream)
                {
                    fileStream.Close();
                }
            }
        }

void NewGamePhysics.Physics.GravityEarthGfcGrid.UnloadGravityMap

(

)

Dispose of the current gravity map.

Definition at line 207 of file GravityEarthGfcGrid.cs.

        {
            this.grid = null;
        }

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Property Documentation

int NewGamePhysics.Physics.GravityEarthGfcGrid.Size [get]

Gets the number of gridpoints loaded.

Definition at line 73 of file GravityEarthGfcGrid.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/GravityEarthGfcGrid.cs