Note on DSS Version 6 versus DSS Version 7 grid records.

[ktarbet]

The DSS C/Fortran library hec-dss does not support writing DSS6 Grids. However, hec-dss has some support for Reading DSS6 grids. That same limitation is passed onto pydsstools, or any Non-Java tool or application. The intent is for hec-dss to focus on DSS Version 7 and retire the DSS 6 Java/Fortran based file format.

Tools such as HMS, DSSVue, and Vortex use underlying Java libraries that support both DSS6 and DSS7 files. The feature of Writing DSS6 girds is performed with both Java and hec-dss . For DSS6 grids Java defines the byte order of data and hec-dss performs the disk IO. For DSS7 grids hec-dss performs all the steps.

Developers seeking a pure C, or non-Java stack have used a pattern of working with DSS 7 files, and converting to DSS 6 only as needed. For example Cumulus uses DSS7 for cloud based processing of grids, and relies on Windows client side apps to convert to DSS6 when needed.

[gyanz]

@ktarbet Thanks for posting this useful information. I am curious about your statement that HMS supports both DSS6 and DSS7. Does this mean HMS is able to read DSS7 grid data?

[ktarbet]

I think HMS can read DSS 7 grids. @tombrauer would you please confirm?

[tombrauer]

HEC-HMS can read both 6 and 7. HEC-HMS will write in DSS version 6 by default. We are working on a full adoption of DSS 7 where we would write to DSS 7 by default, rather than 6.

[gyanz]

@tombrauer What is the minimum HEC-HMS version that supports DSS 7?

[tombrauer]

@gyanz I can't say with certainty without doing some testing. I would guess v4.4. Could be v4.3.

[tombrauer]

From the commit history, it looks like DSS7 read capability started in v4.3, released in September 2018.

[gyanz]

@ktarbet In your earlier statement, you mentioned that a Java library defines the byte order, and hec-dss manages the input and output operations for DSS6 grid in HEC's application. Is the source code of the Java library publicly accessible? If so, could you share it with me, as I would like to incorporate it into pydsstools?