YTGen (Yield Table Generator) is software for generating yield estimates in a production forestry
context. The prediction of yields by log grade often referred to as MARVL* (Method for Assessment of Recoverable Volume by Logtype) and is based on a forest inventory. Many decisions require estimates of yield and YTGEN provides this data to allow decisions to be made.


The following steps are required to generate forest yields:

  1. Measure & describe a sample of trees in plots (forest inventory)
  2. “Grow” plots and the trees in them
  3. Convert trees into logs
  4. Add the logs up by plot
  5. Average the plots across strata and populations

YTGEN provides the functions for completing steps 2-5, as outlined below:


The primary output is a set of estimates of yield for user defined log grades for one or more periods. Optional detailed output includes the input tree list, adjusted for growth and thinning effects, with individual logs generated by the bucking algorithm.

Here are some of the key design philosophies behind YTGEN :

  • Do a few things well: grow trees, cut them up and add them up.
  • Separate yield generation from inventory data collection because:
    • The operational aspects of data collection are organization specific and evolving.
    • Forest measurement data often has a life-span well in excess of the life-span of software.
    • New software must support old data.
  • Separate yield generation from decision support because:
    • Many decision support tools will use the same yield estimates
    • Generating a complete resource description for a forest estate is too time-consuming to do
  • Integrate well with upstream and downstream processes.

Data Inputs and Outputs
YTGEN prepares data from a number of common sources, such as MARVL Version 2 or 3 historic inventory data formats, text file or direct input, through to YTGEN partner product PLOTSAFE, which is a Windows CE handheld application. This is converted to a YTGEN Population file. Combined with cutting strategies and a method reference file (models), these produce outputs from basic population yields through to detailed log output. There is also customized output formats for decision support tools like FOPLI and Woodstock.


Software and Operating Environment
YTGen currently runs on Windows 95 through to Vista. There are three independent applications which are provided as part of YTGEN:

  • Firstly users have the ability to use a fully interactive Windows application for creating and editing populations, cutting strategies and other file types (example view below).
  • There is also a Command-line application for batch processing, typically users may use this under custom script control to automate processing in some line of business application.
  • And finally some users have using the YTGEN COM object for embedding processing functions within spreadsheets, GIS and other COM aware applications.


History and Status
YTGen has been in use in a production forest environment since April 2001. It is commercially
available and currently used by 18 forestry companies in Australasia (as of April 2007). YTGen is owned and licensed by Silmetra Limited.

Silmetra and Interpine jointly provide training courses in YTGEN on a regular basis. YTGEN actively used at Interpine, and is available for our clients to produce forest yields.

* MARVL – although this term has been software product name in the past (developed by Forest Research). It is now a common acronym for the method and process.


Article File Note: David Herries is Interpine’s General Manager, and provides regular training and assistance for YTGEN users.