Forest Inventory Group

Nearest neighbor photo extrapolation

This is not cruising from aerial photos to determine a timber stand's volume; rather this method has us doing an office review to match similar volume "child" stands with previously cruised "parent" stands. The parent stands can be created by us doing new field cruises or from old cruise data provided by the client. Many child stands can be matched to a parent stand by an experienced cruiser evaluating stand density and relative crown heights. Research has shown that we can utilize this method to achieve tract-level accuracies within 7% of the actual volumes. At the polygon level our photo extrapolations are the equivalent of completing 2 standard cruise plots in the stand. This method can be very effective where the client requires inventory figures in a hurry, such as a sale evaluation, or if his stands are in expensive-to-access areas. This method should not be used if sufficient time and/or funds are available to complete enough cruise plots to achieve a minimum 10% sampling error.

Extrapolation Cost Comparison:
Following are the associated costs for the alternative nearest neighbor extrapolation service offered Forest Inventory Group. This method requires creating 15 "parent" stands by entering old inventory plot data, provided by the timberland-owner, into the SUPERACE cruise software. Then we utilize a special sorting program and individual judgment to match each of the 100 non-cruised "child" polygons to one of the 15 "parent" polygons. Actual data provided by the parent stands can then be copied right into each child stand, giving each child its own individual inventory characteristics. The volume sum for all of the 100 extrapolated polygons can then be expected to be within 7% of the actual volume.

Table 2. Photo Extrapolation Procedure Cost for all 100 acre polygons.
Specific Requirement	Units	Cost$/Unit	Totals $
Office: create parent stands	2 man-days	500.00	1,000.00
Office: extrapolate 100 stands	3 man-days	500.00	1,500.00
Office: compile and complete report	1 man-day	500.00	500.00
	6 man-days	total	$ 3,000.00

Summary: As shown by our example calculations, the cost to cruise these 100 polygons, using the conventional inventory method, would be $19,460 and take 4 weeks to complete. If the client is in a big hurry, or many of his stands are in expensive-to-access remote areas, two of our associates could extrapolate all 100 polygons in less than a week and the cost would only be $3,000.

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