Prototype and description of the function convntvascii2bin() (Function of the unlock requiring group "NTv2 grid data")
 convntvascii2bin() Convert ASCII file with NTv2 grid data to binary. Prototype of the DLL function in C++ syntax (attend lower case!): extern "C" __declspec(dllimport) unsigned long __stdcall convntvascii2bin( char *pszFileAscii); Prototype of the DLL function in Visual Objects syntax: _DLL function convntvascii2bin(; pszFileAscii AS PSZ); // 4 Byte, char* as logic pascal:geodll32.convntvascii2bin // 4 Byte The function converts an ASCII file with NTv2 grid data to a more efficient binary file, which can be used for Reference System Transitions using grid shift data. You can download the NTv2 files supported by GeoDLL directly from the KilletSoft Internet site "http://www.killetsoft.de", product descriptions of "TRANSDAT" or GeoDLL" or use the download links to the original sources there. After unpacking the ZIP compressed data they are present as ASCII data files or ready for use as binary files. To be able to use an ASCII file with GeoDLL functions, first it must be converted to the substantially more efficient and more compact binary data format. The conversion can take time up to 10 seconds. Since the function due to the extensive calculations is time-consuming, the event handling during the calculation by interrupting the processing loop can be are allowed bei calling the function seteventloop(). The file name of the ASCII file needed for the Reference System Transition may contain a drive letter and a directory path. The ASCII file may also contain a file name extension. The produced binary file has the same name as the ASCII file, but with the file name extension "gsb". It is produced in the same directory. Example: ASCII file "c:\programm_ntv2daten\BeTA2007.gsa" Binäry file "c:\programm_ntv2daten\beta2007.gsb" Attention, in C syntax double backslashes must be used! The parameters are passed and/or returned as follows: pszFileAscii File name of the ASCII file which is to be converted. The file name may contain a drive letter, a directory path and a file name extension. returnVal In case of an error the function returns FALSE, otherwise TRUE. Deviation from the NTv2 standard inside the NTv2 ASCII file: 1. Anything following a # will be considered a comment and will be ignored. 2. Maximum line length including comments and CRLF is 82 characters. 3. Whitespace is used to delimit tokens in each line, but leading and trailing whitespace is ignored. 4. Blank lines are discarded. This is done after removing any comments and all leading and trailing whitespace. 5. Grid mesh records contain either two or four floating point values: Lat-shift Lon-shift [Lat-accuracy Lon-accuracy]. If the accuracies are not specified, they are assumed to be 0.0. 6. GeoDLL supports Polygonal Validity Scopes. thus grid mesh records may contain the exopolygonal entries -99/-99 in their shift or accuracy values. Detailed information can be found in the help section "Polygonal Validity Scopes". Unlocking This function is a component of the unlock requiring function group "NTv2 grid data". It is unlocked for unrestricted use together with the other functions of the group by passing the unlock parameters, acquired from the software distribution company, trough the function setunlockcode(). Without unlocking only a few function calls for test purposes (shareware principle) are possible. It should be noted that in addition the function group "Coordinate Transformations" must be unlocked.