Prototype and description of the function convelev03ascii2bin()

(Function of the unlock requiring group "Elevation calculations")

 

convelev03ascii2bin()
Convert ASCII file of the 3 sec. elevation model CGIAR to binary.

Prototype of the DLL function in C++ syntax (attend lower case!):
extern "C" __declspec(dllimport) unsigned long __stdcall convelev03ascii2bin(
     char *pszFileAscii);

Prototype of the DLL function in Visual Objects syntax:
_DLL function convelev03ascii2bin(;
     pszFileAscii AS PSZ);                    // 4 Byte, char*
as logic pascal:geodll32.convelev03ascii2bin  // 4 Byte


The function converts an ASCII file of the 3 sec. elevation model
(90 m raster) CGIAR to a more efficient binary file, which can be used for
elevation calculations.

You can download the data of the 3 seconds elevation model from the Internet
site of the "CGIAR Consortium for Spatial information". The current Internet
address is "http://srtm.csi.cgiar.org/". Click in the navigation column on
the link "SRTM Data Search and Download". Activate the radio buttons
"Multiple Selection" and "ArcInfo ASCII". Click inside the world raster map
on the segments, from which you need elevation data. Confirm your
selection with the Button "Search". In a new window the segments you
selected are arranged for the download. Click on one of the links "Data
Download (FTP)" or to "Data Download (HTTP)" for each data segment you need
to copy the data to your computer.

After unpacking the ZIP compressed data they are present as ASCII data
files. To be able to use the data with GeoDLL functions, first they must be
converted to the substantially more efficient and more compact binary data
format. The conversion is done either automatically with first access by the
function getelevation03() or independently with the function
convelev03ascii2bin(). The conversion can take a long time up to a half
minute.

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 conversion may contain a
drive letter and a directory path. The ASCII file must have the file name
extension ".ASC". The produced binary file has the same name as the ASCII
file, but without the file name extension. It is produced in the same
directory.
Example:
ASCII file  "c:\program_elevation\03_sec\SRTM_38_02.ASC"
Binary file "c:\program_elevation\03_sec\SRTM_38_02"
Attention, in C syntax double backslashes must be used!

ASCCI files of the CGIAR versions 2 through 4 are supported. This fle
formats are possible:
Example of a file name in CGIAR V2 syntax:        Z_38_2.ASC.
Example of a file name in CGIAR V3/V4 syntax: SRTM_38_02.ASC.
The file names are not upper or lower case sensitive.

You can order CD-ROMs, DVDs or an external hard disk with already to the
binary data format converted elevation data directly from KilletSoft.
Internet address: http://www.killetsoft.de/p_gdlfhb_e.htm.
Thereby the elevation data are passed free of charge. They are subject to
the copyright of the "CGIAR Consortium for Spatial information". Only a
small copying fee and the costs of the data medium must be paid.


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 and the directory path.
              The file name extension must read ".ASC".

returnVal     In case of an error the function returns FALSE, otherwise TRUE.


Unlocking
This function is a component of the unlock requiring function group
"Elevation calculations". 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.