DESCRIPTION OF FILES: "WW15MGH.EXE" = self extracting file (compressed via "lha" utility), world-wide 15 minute gridded geoid heights. The extracted name is "WW15MGH.GRD"., "WW15MGH.GRD.Z" = UNIX compressed version of the worldwide 15 minute gridded geoid heights. The uncompressed name is "WW15MGH.GRD"., "INTPT.F" = FORTRAN program to interpolate values from "WW15MGH.GRD"., "OUTINTPT.DAT" = test output data to check "INTPT.F"., "INPUT.DAT" = test input data to check "INTPT.F" and "F477.F"., "F477.F" = FORTRAN program designed for the calculation of a geoid undulation at a point whose latitude and longitude is specified. The program is designed to use the potential coefficient model EGM96 and a set of spherical harmonic coefficients of a correction term ("CORRCOEF")., "OUTF477.DAT" = test output data to check "F477.F"., "EGM96.EXE" = self extracting file (compressed via "lha" utility), NASA/NIMA spherical harmonic potential coefficient set, complete to degree and order 360. The extracted name is "EGM96"., "EGM96.Z" = UNIX compressed version of the NASA/NIMA spherical harmonic potential coefficient set, complete to degree and order 360. The uncompressed name is "EGM96"., "CORRCOEF.EXE" = self extracting file (compressed via "lha" utility), Spherical harmonic coefficients of a correction term, complete to degree and order 360. The extracted name is "CORRCOEF"., "CORRCOEF.Z" = UNIX compressed version of the spherical harmonic coefficients of a correction term, complete to degree order 360. The uncompressed name is "CORRCOEF"., "README.TXT" = the file you are currently reading. ------------------------------------------------------------------------------- For MS-DOS users, the world-wide file containing a 15 minute grid of point geoid heights is: "WW15MGH.EXE" This is a self extracting compressed file. To uncompress this file after downloading to your PC, just type "WW15MGH.EXE" at your command line. The resulting "uncompressed" file is: "WW15MGH.GRD" For UNIX users, the world-wide file containing a 15 minute grid of point geoid heights is: "WW15MGH.GRD.Z" This is a UNIX compressed file. To uncompress this file after downloading to your PC, just type "uncompress WW15MGH.GRD.Z" at the command line. The resulting "uncompressed file is: "WW15MGH.GRD" This file contains 1038961 point values in grid form. The first row of the file is the "header" of the file and shows the south, north, west, and east limits of the file followed by the grid spacing in n-s and e-w. All values in the "header" are in DECIMAL DEGREES. The geoid undulation grid is computed at 15 arc minute spacings in north/south and east/west with the new "EGM96" spherical harmonic potential coefficient set complete to degree and order 360 and a geoid height correction value computed from a set of spherical harmonic coefficients ("CORRCOEF"), also to degree and order 360. The file is arranged from north to south, west to east (i.e., the data after the header is the north most latitude band and is ordered from west to east). The coverage of this file is: 90.00 N +------------------+ | | | 15' spacing N/S | | | | | | 15' spacing E/W | | | -90.00 N +------------------+ 0.00 E 360.00 E ------------------------------------------------------------------------------- The program to interpolate point values from "WW15MGH.GRD" is: "INTPT.F" This program interpolates point values from a given gridded file using bilinear or spline interpolation depending on the value of parameter "IWINDO". Check the subroutine "INTERP" within the body of "INTPT.F" for more information concerning the setting of "IWINDO". "INTPT.F" requires two files to run. The first file is the gridded data file, in this case, "WW15MGH.GRD", and is described above. The second file is a file containing the latitude and longitude (in decimal degrees) corresponding to the location of desired interpolation. The input file should be in the following form (cf. "INPUT.DAT"): 38.628155 269.779155 -14.621217 305.021114 46.874319 102.448729 -23.617446 133.874712 38.625473 359.999500 -00.466744 0.002300 LATITUDE LONGITUDE decimal degrees NOTE: "INTPT.F" reads this file in free-format. After running "INTPT.F" a third file is created and is named "OUTINTPT.DAT". This file contains the interpolated geoid heights from "WW15MGH.GRD" at the locations in the file "INPUT.DAT". A sample output (cf. "OUTINTPT.DAT") is given as: 38.6281550 269.7791550 -31.628 -14.6212170 305.0211140 -2.969 46.8743190 102.4487290 -43.575 -23.6174460 133.8747120 15.871 38.6254730 359.9995000 50.066 -.4667440 .0023000 17.329 LATITUDE LONGITUDE GEOID HEIGHT decimal degrees meters ------------------------------------------------------------------------------- The program "F477.F" is provided to compute point geoid height values using the "EGM96" spherical harmonic potential coefficient set and the "CORRCOEF" spherical harmonic correction coefficient both complete to degree and order 360. Both coefficient files have compressed versions for either MS-DOS or UNIX. To uncompress these files, use the method appropriate to your operating system as described for the 15 minute gridded geoid height file "WW15MGH.GRD". The input files consist of: correction coefficient set ("CORRCOEF") => UNIT = 1 potential coefficient set ("EGM96") => UNIT = 12 points at which to compute (INPUT.DAT") => UNIT = 14 The output file is: computed geoid heights ("OUTF477") => UNIT = 20 Files "INPUT.DAT" and "OUTF477.DAT" are in the same format as described above. ------------------------------------------------------------------------------- Files "INPUT.DAT", "OUTINTPT.DAT", and "OUTF477.DAT" are provided to check that programs "INTPT.F" and "F477.F" are operating correctly on your machine. To run the programs: "INTPT.FOR" 1. Create an input data set named: "INPUT.DAT" This file should be in the previously mentioned format. 2. Compile the program using a FORTRAN compiler. 3. Execute the program. 4. The results should be in file: "OUTINTPT.OUT". "F477.F" 1. Create an input data set named: "INPUT.DAT" This file should be in the previously mentioned format. 2. Compile the program using a FORTRAN compiler. 3. Execute the program. 4. The results should be in file: "OUTF477.OUT". Using the provided file named "INPUT.DAT" as input data, your results should match those in the provided sample output files.