Converting a NEXRAD Rainfall Map into a Flood Inundation Map by ...

Figure 4.12 HMSCaller Model ComponentMap2Map requires the launching and monitoring of external programs toexecute a hydrologic simulation and to determine if the launched application hasterminated and fully completed its output generation before continuing processingand executing the next line of code or the next process in line.The ability to externally call and execute an existing HEC-HMS model iscritical for Map2Map. DOS-based programs have traditionally been called byCommand-Prompt statements that include the name of the application, some typeof execution mode index (switches), and the required arguments representing theinput and processing options. To execute DOS-based programs from an externalapplication, programmers normally use special programming functions (e.g., theShell function in Visual Basic) in charge of launching the external application.For the Map2Map application we are interested in calling an externalprogram from a VB DLL that can be incorporated in as a script tool inside ModelBuilder. Obviously, if the standard ESRI geoprocessing tools (hammer icons)cannot do the required task (a complete hydrologic simulation), an externalprogram needs to be invoked performed a job that is not inherent to GISfunctionalities.103