Consider recommended contract specifications and topics.
For surveys using the growth intercept or site index curve methods,
the following are recommended contract specifications (Figure
- Height: record height to the nearest 10 cm with a maximum error
- Age: record age to the exact year with
- no error on trees <10 years
- maximum 1 year error on trees 10-20 years
- maximum 5% error on trees >20 years.
- It may be difficult to meet these age standards under some field
conditions, so flexibility in checking will be required.
- Species: NO error is acceptable.
Figure 11.1. Some recommended
In some contracts, it is possible (and useful) to specify the method
that should be used to estimate site index. When SI is determined with
the growth intercept or site index curve methods, specify the number
of plots required.
Contract administrators should consider the following topics when developing
or implementing contracts:
- recommend that surveyors take this course
- review SI estimation procedures with the contractor at the viewing
and again at the pre-work
- ensure surveyors attain first few ages by drilling or cutting to
calibrate their eye prior to whorl counting
- consider flagging sample trees as a contract clause.
Provide surveyors with the necessary SI materials:
- SIBEC guide
- GI FS415s and manual
- SI curves
- Decision key
- SI/Site class conversion tables
- SI species conversion tables.
Contract administrators should be prepared to do a GI plot in the field
Tips on how to check a GI survey are provided in Appendix 7.