The time consumption and expenditure for the field work in large-scale inventories are usually insufficiently known.
In this study, the costs of the fieldwork of the second Swiss National Forest Inventory (NFI 2) have been assessed and allocated to different categories, based on records made by the field crews on paper and in portable computers.
The terrestrial inventory (including training and quality control) required 72,851 working hours. The field work on a single plot took an average of almost 9 working hours, i.e. 4.5 hours for the crew. The share of «productive working time» was 35%.
Newly stocked plots and plots assessed in order to check the representativity were assessed for the first time. These plots required 20% more field work compared to subsequent assessments. The main reason was the time used to locate the new plots which is not usually required in repeat inventories. Within the NFI 2, detailed assessments of the forest edge on 1000 plots took slightly more than one working hour for each plot.
An optimal instruction and training of the field crews was essential to get high quality data. The instruction courses at the beginning of each season lasted several days. During the field season, the crews were trained at regular intervals in the assessment of particular variables, using training units lasting two or three days. The instruction and training took 6780 hours or 9.3% of the total working hours. An independent crew made control measures on 752 plots, which required 6702 hours or 9.2% of the total working hours.
The salaries and expenses (without supervision, but including instruction, training and control measurements) for the terrestrial assessments of 7367 plots amounted to 3.54 million Swiss francs. The assessment of one single plot therefore cost Swiss francs 480.–. If the costs for equipment and vehicles are included, each plot cost an additional 71.– Swiss francs.