The model consists of a series of pages below one another. Each page contains boxes enclosing cells where data can be entered or showing internal calculations and results. By pressing the <page down> key, each of the pages appears on the screen.
The top six lines of the spreadsheet are fixed and will appear on every page. This box contains the main results of the analysis and is shown with every page, so that the effect of changing cost and benefit data on the results of an analysis can be clearly seen.
The first page is a title page listing the contents of all the other pages. The remainder of the pages can be considered as falling into four main sections: the data entry section (pages 1 to 9); the worksheet section (pages 10 to 12); the financial tables section (pages 13 to 17); and the calculation, or workstudy, section (pages 18 to 26). The function of each of these sections is described in more detail below.
Figure 1 The Forest Concession Model opening screen
A default set of data has been entered into the model and in addition to this, the model generates cost estimates for a number of road making, harvesting and management activities. Users can change the default data, choose to accept or over-write the model estimates, or change the model estimates by entering their own data on the parameters used to calculate these estimates, depending on the quality and quantity of data available.
Boxes where data can be entered into the model are displayed with a yellow background (or light grey background on black and white monitors) and the text in these boxes is shown in bold. To improve the visual appearance of the model, some of these boxes are more than one cell wide, in which case numerical data should be entered into the cell on the right-hand side of the box and text entries should be entered into the cell on the left-hand side of the box. The worksheet is protected, so it is not possible to enter text or data into cells outside these boxes unless the protection is switched off.
There are a few cells containing data and formulae which cannot be seen. The most common of these are cells which check neighbouring data entry cells for possible mistakes and show an error message if it looks like data has been is a mistype (for example, if negative costs are typed in)[5]. These cells will not display anything unless a mistake is suspected.
Other hidden cells contain internal references for lookup tables and short programmes for printing (see section on printing below). Erasing or overwriting the contents of these cells may cause the model to fail so care should be taken if the worksheet protection is switched off.
[5]. The Model has been designed so that most data entry cells will be checked for the most obvious types of mistake. It is possible however, that some mistakes might not be identified by the model and lead to incorrect results.
