FD2ADDTOPO

Basic Information

Name of Program

FD2ADDTOPO

Version-Date

October 2021

Description-Date

June 2019

Catchwords

finite differences grid (type FIDISOR/FIDIRB)
update of topography
echo soundings

Short Description of Functionality

The program FD2ADDTOPO creates a difference topography from echo soundings in the format of the given example topography (type FIDISOR/FIDIRB). This difference topography (after optional interpolation) is used to update the grid cells of the original topography with new values through direct replacement. The last difference topography can be written into new ASCII files. The program contains three components:

1. procedure GITGENER creates a new difference topography from echo soundings.
2. procedure GITPOL interpolates an already existing or just created difference topography.
3. procedure ADDTOP updates an old topography with values of an already existing or just created difference topography.
4. procedure STORERAS stores the calculated grid cell center points into new ASCII-files (x,y,z). Two modi are possible: the first stores all data into a single file, the second creates a file for each window of one square kilometer size..

With the help of automatically generated input control and batch files it is possible to estimate the quality of echo soundings. For further information please contact the developer of this method.

Input-Files

1. input control file fd2addtopo.dat
   It is possible to generate input control files for the procedure GITGENER automatically. The program gen_fd2addtopo_single.hp generates files that control the procedure for single echo sounding files. The program gen_fd2addtopo_cover.hp generates files that control creating a topography out of echo sounding files that cover the area of a reference topography.
2. (when GITGENER shall be executed or a topography shall be updated with ADDTOP) (example) topography (type topo.bin).
3. (when GITGENER shall be executed) files which contains echo soundings (type geom.dat or FORTRAN format '(2(f10.2,1x),f6.2)'. Other formats with separating blanks are supported too. Packed files are allowed (GZIP, COMPRESS, ZIP)!
4. (when GITPOL or ADDTOP shall run independently from GITGENER) difference topography (type topo.bin).
5. (when GITPOL or ADDTOP shall run independently from GITGENER) compatible mask file for difference topography (type topo.bin.log).
6. (optional) digitized structures (file type digi.gkk). Packed files are allowed (GZIP, COMPRESS, ZIP)!

Output-Files

1. after GITGENER) difference topography (type topo.bin)
2. (after GITGENER) compatible mask file for difference topography (type topo.bin.log).
3. (after GITPOL) interpolated difference topography (type topo.bin)
4. (after GITPOL) compatible mask file for interpolated difference topography (type topo.bin.log).
5. (after ADDTOP) updated topography (type topo.bin).
6. (after STORERAS) one ore several files of type geom.dat or any other (xyz) format.
7. printer output file fd2addtopo.sdr

Methodology

In a first step ( GITGENER ) the program FD2ADDTOPO creates a FIDISOR/FIDIRB topography file which contains actual depth values. The user can define how many echo soundings have to exist at least in a grid cell in order to assign a depth value. To cells with less echo soundings a default value is assigned. Furthermore a histogram with the number of echo soundings per cell is evaluated. The printer output file contains the histogram. Additionally a mask file will be created which contains the information whether a depth value is assigned to a grid cell or not. All cells which are not updated contain the value -99.9 as a dummy depth. The filenames of echo sounding data have to be specified with or without a preceeding sign. The meaning of the sign is as follows: If the sign is "-", the depths are multiplied by -1, otherwise the depths are used as they are given. An avaraging is done for all data which are located in the same grid cell. The following averaging methods can be used:

• 0: alle data are weighted equally with 1.0
• 1: the weightning of data decreases linear with increasing distance to the center of the cell. data points outside the correlation radius have no influence.
• the weightning of data decreases exponentially with increasing distance to the center of the cell.

During the second step ( GITPOL ) depth values for further cells will be interpolated from cells, which contain already a real depth. This step eventually has to run twice for situations with a very scattered distribution of the echo soundings. The step can be suppressed by setting the count of interpolations to 0 inside the input control file. By this interpolation cells are searched inside a region of neighbourhood, which contain valid depths. The search is done radial in eight directions (north, northeast, east, southeast, south, southwest, west, northwest). Then a inverse distance weighted average of the found depth values is calculated (simple Shepard interpolation). During the third step ( ADDTOP ) depth values of the (example) topography are updated where they exist.

Remark: Coordinates of raw data files are now transformed to a user defined coordinate reference systen (CRS) if necessary. To support this feature, the user must include a magic comment with the content "C CRS=xxxxx" at the beginning of the file. Here "xxxxx" stands for the EPSG code of the CRS. Additionally the user has to set the environment variable BAWCRS to a valid CRS. All Input files of type topo.bin must be realized in this user CRS.

For supported EPSG codes see GEOTRANSFORMER! For the coordinate shift from DHDN/STN to ETRS89 the NTv2 method is used with the grid shift files, which are defined by NTV2GRID (DHDN) and NTV2STN (STN).

Program(s) to run before this Program

Digitizer (PC), FD2BASIS, FDGITTER05

Program(s) to run after this Program

FD2DEL, FD2TRIM, FDGITTER05, GISMO

Additional Information

Language

Fortran2003

Additional software

-

Original Version

M. Boehlich, G. Seiß

Maintenance

working group PRE

Documentation/Literature

$PROGHOME/examples/fd2addtopo/*

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