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Chapter VIII
FOREST MENSURATION

FOREST mensuration is the science of measuring thecontents of standing or felled timber, and estimating growth and yields.Foresters, timber owners, and farmers owning woodlands should know theessentials of timber measurement. A pioneer storekeeper who believedthat "a pint's a pound the world around" developed a sizable trade inshot with local hunters. He more than likely failed as a merchant.Likewise timber owners, who do not recognize the value of forestmensuration, may make transactions in forest products to their owndisadvantage, but to the decided advantage of dealers.

When there was an abundance of low-cost timber andcheap labor, lumbermen did not find it necessary to make precisemeasurements. Transactions involving vast timbered areas were based onsuperficial estimates. Today, however, because of limited quantities oftimber and increased production costs, timbermen, in keeping withpresent business practice, find it necessary to make closer estimatesof timber volume.

Knowledge of Measurement Is Essential.



"A Pint's a Pound."




"Waste Not, Want Not."

UNITS OF MEASUREMENT

The board foot: A knowledge of the basic unitsof measure is necessary before an attempt can be made to learn theprocesses of mensuration. The unit of measure for lumber is the boardfoot. A board foot is a piece of wood 1 foot square and 1 inchthick, or its equivalent. A board an inch thick, 12 inches wide, and 10feet long contains 10 board feet. An inch board 8 inches wide and18 feet long contains 12 board feet; a 2-inchplank 6 inches wide and 8 feet long contains 8 board feet.Volumes of boards less than an inch thick are usually estimated as ifthey were an inch thick.

The cord: Fuel wood, pulpwood, and similarbulk wood is measured by the cord. A standard cord is a stack of wood 4feet wide, 4 feet high, and 8 feet hong. It has a cubical measure of 128cubic feet, but there are spaces between the pieces of wood in thestack. The actual volume of wood is from 70 to 90 cubic feet. Seasoningmay reduce the actual wood content of a cord of green wood as much as 10or 15 percent. Some pulpwood is cut 5 feet long, and fuel wood is cutless than 4 feet long, depending on sizes of stoves and fireplaces.Such wood regardless of length, stacked 8 feet long and 4 feet high, iscommonly called a cord, although it is not standard size.

Piece measurement: Some wood products are soldby the piece. Poles, piles, posts, ties, and staves are in thisclassification. Poles and piles are cut in different sizes governed byparticular needs. Posts have no exact dimensions, but a standard post issaid to be 4 inches thick, 5 inches wide, and 7 feet long. Standardrailroad ties are 7 inches thick, 9 inches wide, and 9 feet long. Theseproducts are bought by the piece. Stave and shingle bolts are bought bythe hundred.

Cubical measurement: Very valuable woods, suchas mahogany or dyewoods, are usuallymeasured by the cubic foot. A cubic foot is a solid,a foot long, a foot wide, and a foot thick.

Acreage: Stumpage (standing timber) is sometimesmeasured and bought by the acre. This is more common for pulpwoodmeasurement than for other products, and is used extensively by largepaper-mill operators of Canada.




A Piece of Wood 1 by 12 by 12 Inches.












When lumber was cut in mills of this type, precise timber measurement was notpracticed.













The Standard Cord.

See Timbers, pp. 152, 155.










What is Stumpage?


CRUISING

Estimating the volume of standing timber is known ascruising. The most reliable method of cruising is based upon asystematic use of measuring instruments and practices. This is calledthe systematic cruise. The volume of the trees on a representativeor average portion of the forest is estimated, and the total volumecalculated, based upon the volume of the part which was measured.

CRUISING INSTRUMENTS

The amount of wood in a tree is determined bymeasurement of its diameter and height. Special instruments have beendeveloped for use in cruising. It is desirable that one be acquaintedwith those commonly used.

Diameter measurement: For measuringdiameters, the caliper is the most common instrument. It is a heavy ruleusually about 3 feet long, but longer for use on the very large trees.At one end of the rule a rigid arm extends at right angles, the rule andthe fixed arm forming an L. Another sliding arm is attached also atright angles to the rule. The caliper is opened and the arms placed oneach side of the tree trunk. The sliding arm is then moved close againstthe trunk, and the diameter read on the graduated (marked in units)ruler. If a tree trunk is oval instead of round, the longest and theshortest diameters are taken and averaged.

A tape may also be used to take diameter measurement.The circumference of the tree is measured and the diametercalculated by dividing the circumference by 3.1416. This is based on thefact that for every inch in the diameter of a perfect circle there are3.1416 inches in the circumference. Diameter tapes on which thesecalculations may be read are available. With these tapesthe cruiser reads diameters of the trees, instead ofinches in circumference. Large trees may be measured by attaching thehooked end of the tape to the bark and running the tape around thetrunk. With a tape, however, it is impossible to average the diametersof trees having oval-shaped trunks. A small fraction of theirmeasurement is deducted if the tree has an oval shape.

The Biltmore stick is a rule graduated to indicatethe diameter of a tree. The rule is placed against the trunk of the treeat a tangent. With the eye about 25 inches away (average arm length),the diameter may be read by lining up the end of the stick with the lineof vision to one side of the trunk and sighting across the rule to theother side. At the point where the line of vision crosses the stick, thegraduation will indicate the diameter of the tree.

Height measurement: Heights of trees may bemeasured by an Abney hand level. The Abney is a pocket instrument formeasuring angles or per cent of elevation. (See chapter on Forest Engineering.)For tree measurement, the scale on the instrument shouldindicate elevations in percent; that is, it should be equipped with apercentage arc or limb.

The operator of the level stands a hundred feet fromthe tree and sights the instrument at the topof the tree or at the merchantable height. Thenwithout moving the instrument, the level bulb attached to the side isadjusted to a level (horizontal) position. An indicator on the leveltube indicates the percent of elevation on the graduated arc. Theinstrument is then sighted on the base of the tree and the percentageread. These two readings are added (subtracted if the eye of theinstrument operator is below the base of the tree) and the sum (ordifference if subtracted) of the two readings is the height of the treein feet.

There are many phases of measurement with the Abneyimpossible to describe in limited space. For details and fullinstructions, see Forest Mensuration by Bruce andSchumacher1 or an Abney Handbook.2


1Forest Mensuration, pp. 16-17. DonaldBruce and Francis Schumacher, McGraw-Hill Book Co., Inc., New York1930.

2The Abney Level Handbook, pp. 10-19.H. A. Calkins and J. B. Yule, U. S. Forest Service. For sale bySuperintendent of Documents, Washington, D. C. Price 5 cents.


An instrument for measuring heights of trees iscalled a hypsometer. There are many kinds of hypsometers, butonly a few will be mentioned. The Forest Service hypsometer is probablythe best one on the market. It works on the same principle as the Abneylevel, but a gravity bob, instead of a level bulb, is used to indicatethe tree's height. The little plumb bob and the graduated arc areenclosed in a case. On one side of the case is an eye piece or peep holeand on the other side a little window through which the tree top may beseen. Sighting at the top of the tree at a distance of 100 feet from itsbase, the operator reads the tree's height on the movable scale.

The Merrit hypsometer is a very simple one,consisting of a rule graduated somewhat like the Biltmore stick,previously described. The cruiser, using a Merrit hypsometer, faces thetree at a fixed distance (usually 66 feet) holding the rule verticallyat arms length. He holds the base of the rule on his line of sight tothe base of the tree, sighting just under the bottom of the upright ruleto the base of the tree. Without moving the rule or changing hisposition, he sights at the top of the tree. The marking on therule which lies in his line of sight to the top of the tree willindicate the height of the tree.

The Christen hypsometer is another simple instrumentconsisting of a rule or scale about 10 inches long which may be foldedand carried in the pocket. The cruiser, facing the tree at sufficientdistance to permit him to see its top and base, holds the instrumentvertically before him. An assistant holds a 10-foot pole upright at thebase of the tree. The cruiser moves the scale nearer or away from theeye until the whole length of the scale just covers the entire view (inheight) of the tree. The marking on the scale which is on the line ofsight with the top of the upright pole indicates the height of thetree.

CRUISING PRACTICES

Although cruising may be done by one experiencedcruiser alone, he usually has a crew of assistants. Their job is tomeasure the diameters and heights of trees in a portion of the forestand to estimate total timber volumes from this data. In most cruisesonly enough height measurements are taken in each species to make heighttables. By taking both diameter measurement and height measurement on asufficient number of trees, average heights for different diameters ineach species may be found.

For example, in a definite locality, yellow pineswith 16-inch diameters will average 38 feet of merchantable height, andtrees of the same species having 20-inch diameters will average 46 feetof merchantable logs. In the same locality it may be found that red oakwith 16- and 20-inch diameters average 28 and 35 feet, respectively.After such local tables are made, it is necessary only to measurediameters. Heights are then calculated from the tables. In cruisesrequiring more precision, each tree height may be measured separately.On cruises requiring less precision, all heights may be estimated byeye.

The systematic cruise: Under the systematicmethod, it is necessary for men to work in crews. The average-sized crewis composed of an experienced cruiser and three assistants, butthree-man crews may work on some estimates, and a five- or six-man crew may alsowork to advantage, especially where hypsometer measurements aretaken.

A CREW AT WORK

A four-man timber estimating crew using the stripmethod works somewhat as follows: A compass man, using a ForestService compass, or a hand compass, starts on a compass line through thewoods about 20 rods from one of the boundary lines of the tract. He goesup the slope of a hill rather than along the side because differentaltitudes and soils affect the size of trees, and better samples of thestand are obtained by this method than by working along the sides ofslopes. The compass man drags a surveyor's chain tied to his belt as hewalks along his course. The chief of the party, an experienced man,follows at the end of the chain and halts the compass man when one chainhas been measured. These two men stop, and the forward man takes noteson topography, streams, and roads, and makes a rough map of theforest.

Beginning at the rear end of the chain, each caliperman paces off two rods on each side, or the leader, who acts as a tallyman, assists in measuring this distance. The caliper men then beginmeasuring the diameters of the trees and calling out their sizes to thetally man, who records them in his tally book. Defective trees arecalipered and called, even if they are culls (trees unfit for lumber).One caliper man may call, "White oak, 23." The tally man records this inhis tally book. The caliper man on the other side of the line then calls"Yellow poplar, 34." This is tallied and the first caller reports,"Maple, 19," and the second one, "Beech, 28, cull." No fractions ofinches are called, because in diameter measurements such fractions aredisregarded. Instruments are read to the nearest inch. If actualmeasurement falls on a half-inch mark, the nearest even inch is read.For example, both 19-1/2 and 20-1/2 are read as 20, or 21-1/2 and 22-1/2as 22. (In height and length measurements, the same practice is appliedto feet and fractions of feet.) The diameters are measured about 4-1/2feet from the ground. This height is handy for the workmen and is abovethe swell of the stump. This is called "diameter breast high" and isoften abbreviated to D. B. H. All the trees above a minimum diameter onthe four-rod strip are Strip method, measured and recorded. Thetally man walks along the compass line and inspects defective trees,estimating the usable part in each.

If hypsometer readings are also being taken, two menusually work on each side of the compass line, one measuring diameter,the other estimating height of a tree at the same time. Two measurementsare called to the tally man instead of one.

When the forward end of the chain is reached, thecompass man moves forward again; the leader follows and halts him whenthe end of the chain reaches the mark made on the ground by the compasscarrier at the position of the first halt. The procedure of measuringand tallying is repeated until the opposite boundary of the forest isreached.

After the strip is finished, the compass operator,with the help of another man, chains off 40 rods at right angles to theline just run. This is the center line of the return strip to be run back acrossthe forest, Strips spaced at this distance give a 10 percent estimate ofthe whole forest. For a 20 percent estimate, the compass lines arespaced 20 rods apart (or 10 rods apart when the strip is reduced to 2rods in width).

The plot method: Some cruises are made by theplot method rather than by strips. Under the plot methods the compassline is run as described in cruising strips. Plots are measured atcertain distances apart along the line, instead of in a continuousstrip. The plots may be square, circular, or oblong. The square acremay be paced (70 yards on each side) by the compass man. The circularacre has a radius of 118 feet or 39-1/3 yards. The oblong acre—1chain wide (66 feet) and 10 chains long—is probably most practical.This can easily be measured along the compass line and trees caliperedas in the strip method. The percentage of trees to be measured in thecruise will determine the distance between the plots. Smaller plots ofone-half to one-eighth acre are often used.

The ocular cruise: An expert cruiser may beable to make a fair timber estimate without the systematic use ofinstruments. He walks through the stand and examines the trees. Bycarefully noting the sizes and numbers of trees, he can make anestimate. Such a method of cruising is called the ocular method,because the eye is principally used to estimate sizes. The estimator,under this system, may carry pocket instruments, such as hypsoineter anddiameter tape, to check tree measurements. He may locate sample plotswith average stand, pace off an acre, and count the average-size trees,thus arriving at an estimate of the total volume. Each cruiser uses hisown methods based upon his experience and practice.

The sample cruise: The sample method ofcruising requires enough systematic measurement to find the volume ofthe sample tree of each species in a forest or locality. The sample treeis an average-size tree of any one species. After the sample is found,cruising consists of counting trees only. This may be done on strips orplots as desired. Sometimes, when no average sample has been found, countsmay be made, every twenty-fifth or fiftieth tree measured, and when the entirecount is completed the average volumes calculated from the treesmeasured.

For extensive counting the cruiser carries amechanical counter which fits in the hand. A small lever is pressed withthe thumb to register each tree. The total number is recorded and may beread from a dial on the instrument and recorded. The counter registersup to 999 and then repeats. One cruiser may make counts in two speciesat the same time by carrying a counter in each hand.

Aerial estimation: Although timber cruising byaerial photography is in its infancy, many foresters believe that ithas great possibilities. A series of vertical pictures covering theentire forest area are taken from an airplane (the camera beingdirected straight down). These are mounted, oriented, and fitted to showa complete photograph of the forest. Elevation, streams,trails, and other landmarks stand out clearly, anddifferent species and timber types may be identified if the picturesare taken in spring while leaf colors are fresh or in late autumn beforeleaves fall. Aerial photographs are used principally in mapping andlocating types and stands. After they are located, direct measurement istaken to get averages in each type.

Rule of thumb: Foresters and woodsmen knowrules of thumb by which they can estimate the contents of a treeor log in board feet without the use of a volume table. A rule of thumbis a simple formula which may be easily applied in measurement. Probablythe most common one is based upon Doyle's log rule, explained later. Itgives the volume of a standard 16-foot log. The rule of thumb is asfollows: Subtract 4 inches from the diameter of the small endof the log inside the bark, and square the remainder. The result isthe board-foot content of the log. If the tree has more than one log,the average diameter inside the bark should be estimated, and the samecalculations made. Multiply the results by the number of 16-foot logs inthe tree. For instance, a tree with a 40-foot merchantable trunk wouldcontain two and a half 16-foot logs. This rule gives high results for athree- or four-log tree. The small-end diameter of each 16-foot log insuch trees may be estimated. The 4 inches deducted from the diameterunder Doyle's rule is to compensate for sawdust and slabs—wasteproducts of the sawmill operation.

Volume tables: For converting the measurementof diameters and heights of trees in a stand to board feet of lumber,volume tables are used. Such tables show how many board feet of lumbercan be sawed from trees of different diameters and heights. Volumetables are most accurately made by measuring a number of treescarefully, following each of them through the mill, and measuring thevolume of lumber sawed from each one. In this way the amount of lumberwhich can be expected from trees of certain size is known, and thenumber of board feet of lumber in a forest may be estimated.





The Systematic Cruise.







Calipers for diameter measurement.


Average diameter is found for oval logs.

Diameter Tapes.


Diameter Tapes.






Diameter measurements may be taken with diameter tape or cruising stick.











Abney level.


Using the Abney level.

Hypsometers.


Measuring tree height with Merrit hypsometer: Height BC, is indicated on scale DE.


Method of using Christen hypsometer.






Height Tables.








Height Averages Based upon Diameters.








Sizes of Crews.

















Members of CCC cruising timber.














They Start.


Plan of strip cruise.

Calipering Trees.

Tallying.





Strip method.









They Finish the Strip.




The Offset Line.


The Return Strip.


Plot method.

Square, Oblong, or Circular Acres.


The system of dots and lines used by foresters in tallying.

Experience Instead of Instruments.

Each Ocular Cruiser Uses Own Methods.

The Sample Method.















The seasoned woodsman estimates tree heights by eye.










Photograph from an Airplane.

Aerial Photography Valuable in Forest Mapping.

Rule of Thumb Simplifies Volume Calculation.






Estimating Tree Volumes by Rule of Thumb.








Checks at the Mill for Volume.


GROWTH STUDIES

Mensuration is used for other purposes thandetermining timber volume. Growth studies demand exceptionally closemeasurements both in diameters and heights. The results of such studiesare valuable in making cutting plans, in solving management problems,and in determining forest policy. Much of the research which has madethe science of forestry possible is based upon accurate measurement.

The farmer harvests his crops annually, measuringthe yield and determining his profit or loss. The forester or timbergrower has to wait long periods to check his harvest. It becomesnecessary, therefore, for him to make growth studies to see what foreststands are yielding. Some stands may be increasing in growth so slowlythat they are not profitable. Forest increment (increase in volume) maybe calculated by accurate measurement.

Counting rings: The sizes of trees at variousages in a particular stand may be found by measuring a number of trees,determining their ages, and relating age to size. If the study is beingmade on a plantation, a record of the age of trees should be available.If not, the best method of determining age is by counting growth rings.Each spring a tree adds a spongy growth just under the bark. In summer,a firmer growth overlays this first one. This growth ofspringwood and summerwood together forms an annualring. These rings may be counted on cross cuts of tree trunks todetermine the age of the tree. The stump of a freshly cut tree shows therings very plainly.

It would be a wasteful practice to fell trees inorder to count rings, and leave them on the ground to rot. If trees arecut to make growth studies, arrangements should be made for using thetimber. It is sometimes possible to combine a growth study with alogging operation. Rings may be counted on the stumps and logs, anddiameter measurements taken inside the bark with an ordinary rule.

Boring: Where it is not possible to makestudies on logging operations, precise measurements in diameter andheight are made, and ages are found by use of an increment borer.This is a gimletlike instrument for boring into the side of the tree. Ithas a hollow bit that bores out a "core" of wood on which the rings maybe counted. It is not necessary to draw a core all the way from thecenter of large trees. The number of rings per inch is calculated, andages of trees thus computed. The increment borer makes a small holewhich soon closes and does not seem to damage trees. Sometimes the holeis plugged with grafting wax to prevent the entrance of insects ordiseases.

Yields: Rainfall, temperature, and soil conditionsgreatly affect the growth of forests. The normal yield isthe yield obtainable from a completely stocked acre of healthy trees inthe locality. The empirical yield is the average increase peracre obtainable from the actual stand of the forest.

Yield tables: Data obtained by growth measurementsmay be used to make yield tables from which future yields may bepredicted. After the average sizes of trees of certain ages have beenfound, they are plotted on cross-section paper—sometimes called graphpaper—and used in making the tables. On a sheet of cross-sectionpaper, volumes are plotted on vertical squares and ages on horizontalsquares. Curves for determining averages are plotted. The same methodsare used in making volume tables either for trees or for logs (logrules). In cruises, heights and diameters may be plotted to obtainaverage heights for certain diameters.

Unless one is fairly familiar with calculations bymeans of cross-section charts, it is impossible to explain formation oftables in a limited space. Refer to any good text book on Forest Mensuration3for detailed explanation of these graphic processes.


3(1) Chapman, Herman H., ForestMensuration; (2) Bruce and Schumacher, Forest Mensuration;(3) Chapman and Demerritt, Forest Mensuration.


TIMBER SURVEYS

A timber survey extends over large areas. Inmaking such a survey several cruising crews may work out of the sameheadquarters or camp, moving from one location to another. Forest areasare located, stands measured and classified, and yields predicted.Tables and maps are made as a record of the survey. The forestsurvey, although based on forest mensuration, includes other factorsthan the actual timber growth, or increment. Soils, drainages, and otherfactors affecting forest production are studied, in addition to timberstands. The crews of a forest survey may be composed of engineers,foresters, and soil experts and their assistants. The forest survey isused extensively by the United States Forest Service in landacquisition. Surveys reveal facts necessary in purchasing areas to beconverted into national forests.





How to Use Growth Studies.





Checking Up on Annual Growth.





See pp. 6, 7.



Logging Operations Permit Easy Count of Rings.



Annual Rings as Shown by Increment Cores.

Determining the Yield.



How to Make Yield Tables.



Use of Cross-Section Paper.

















Timber Cruises Are Valuable in Surveys.




Use of Forest Surveys.


SCALING TIMBER

The measuring of logs to determine their volume inboard feet is called scaling. Logs may be scaled where they arecut in the woods, on landings or skidways, or at the mill. Sincelog-cutting crews are usually paid by the thousand board feet, scalersmay measure logs where they lie, as a basis for paying the crews. Theymay be scaled on skidways as a basis for paying snakers or haulers, andat the mill as a mill check. In connection with log sales, logs areusually scaled by a representative of each party to the contract.

Log rules have been made to facilitate measuring thecontents of logs. By measuring the diameters and lengths of logs, andreferring to the log rule, the volume of lumber contained in a log ofany size may be found.

Scales: Log scales or "scale sticks" have beendevised which simplify scaling practice. They are used to measurediameters and lengths and to estimate volumes. There are many differentscales, based upon various log rules, but they are basically the sameand are used in the same manner. A scale stick is a rule 3 to 4 feet long,somewhat like a common yardstick. It is made of tough hickory or maple,and has a handle at one end and a protecting brass tip at the other. Onsome of the tips there are L extensions which aid in holding the scaleon the end of logs. Others have short, sharp hooks or spurs which may beforced between the bark and the wood. They help to hold the scale on thelog and aid in taking the D. I. B. (diameter inside bark) measurements.Scale sticks are marked in feet and inches along both edges. Thesegraduations are used in measuring the logs. The log-rule values areplaced on the sides of the sticks, one row of figures indicating boardmeasures of logs of given lengths and diameters.

Using the stick: The scaler places the stickon the small end of a log. If, for instance, the figures on the edge ofthe stick show that the log is 17-1/2 inches D. I. B., he calls this 18inches. A fraction of an inch is read thus to the nearest even inch. Thefigures on the side of the stick near the 18-inch mark indicate volumesfor different lengths. If the log is 12 feet long, the scaler locatesthe figure in the row of volumes for 12-foot logs—160 boardfeet.

Variety of scales: There are 20 to 30different log scales in use in the United States, based on different logrules. The Doyle, Scribner, and Spaulding are well-known scales, andmany States have adopted legal scales. These are known by the name ofthe State, for example, the Maine scale.

Log-scale values differ. Some of the differences areradical for certain sizes. An expert in forest mensuration states thatthe use of different scales may make from 5 to 50 percent difference inthe scaled contents of the same log.4 The Doyle scale deducts4 inches from the diameter of the log for mill waste. The scale of a16-foot log with a diameter of 8 inches is reduced 75 percent by thisdeduction. It is evident that this is too great a reduction. No millshould waste three-fourths of an 8-inch log in sawing. The Doyle rule gives alow scale for logs less than 28 inches in diameter.


4Herman H. Chapman, ForestMensuration, p. 88.


The Scribner scale seems to be more reliable. Onlarger logs, however, it has been found by mill tallies that the scaleis low. On a 34-inch log, the Scribner scales 100 feet less than theDoyle rule. It is marked in decimals (units of 10 feet) rather than inexact measures. A mark of 9 on this scale indicates a volume of 85 to 95feet; a mark of 15 indicates a volume of 145 to 155 feet. In a number oflogs scaled by a decimal scale, some may be high, and some low, but theaverage will be the multiple of 10: Thus the two examples would average90 and 150 feet respectively, and would be so tallied.

Log dealers and mill men use a combination of thesetwo rules in the Doyle-Scribner scale. This makes use of the principleof the former rule up to 28-inch diameters and the latter for largerlogs. Thus the portions of each rule have been used which favor the millowners, often to the disadvantage of the timber producer.

Logs may be scaled by a rule of thumb when logs ruleor scale sticks are not available. The rule given for the estimation oftree volume (p. 177) may be used. Diameters of logs may be measured withany convenient instrument and the rule of thumb applied to get volumesof logs of each dimension.

Scaling defective logs: When logs have visibledefects which would decrease the lumber volume, defective parts are"scaled out." Logs with excessive defects may be rejected as culls, Ifenough of the log can be utilized to justify sawing, deductions aremade for the defective part. Rots, hollows, crooks, windshakes, cracks,and sometimes other minor defects are scaled out. The part of the logwhich cannot be used is measured and subtracted from the volume of asound log of the scale dimension.

Overrun: Some sawmills have considerableoverrun of lumber above the scale of the logs. A band sawmill, using a thinsaw, can get more lumber from a log than a mill using a thicker saw.The circular saw cuts an average kerf of about threeeighths inch, while the band saw cuts less than one-fourth inch kerf,The sawyer, by expert handling of the log, can raise the overrun. A log16 feet long has a greater diameter at one end than. at the other, andsince the average diameter is used in scaling, several 10- or 8-footboards which are not included in the scale can be sawed from thislog.

Forest Service practice: The United StatesForest Service has adopted standard scaling regulations to be followed inmeasuring national forest timber. The Scribner decimal C scale is used,and definite instructions are given for scaling out defects. The scalingpractices are fair to purchasers and provide for a small overrun.Complete regulations of Forest Service scaling may be found in the book ofinstructions for scalers.5


5Instructions for the Scaling andMeasurement of National Forest Timber, Forest Service, U. S.Dept. of Agriculture, 35 cents, The Superintendent of Documents,Washington, D. C.









Why Scale Logs?





Log Rules Are Timesavers.

D. I. B.

Log Scales Not Standardized.









Scribner Scale.




Decimal Scales.










Rule of Thumb for Logs.

Overrun.




Lowering Mill Waste.

















Each log is scaled, marked, and tallied.

















U.S.F.S. Standards.


SUMMARY

AN EXAMPLE OF PRACTICAL FOREST MENSURATION

A forest owner has an area of matured timber that hewants to sell. Before advertising it, he employs an experienced timbercruiser to make an estimate of the quantity of timber on the area. Thecruiser goes into the woods alone, and by using pocket instruments foroccasional checks on diameters and heights, and by counting trees onaverage plots which he has paced off, he calculates the volume of sawtimber per acre. By examining records of previous surveys of the area,the cruiser determines the total acreage of the tract of land. Hecalculates the total volume of timber and reports to the timberowner.

The owner advertises his timber for sale. He sets astumpage price. A timber dealer needs the timber, but it is necessaryfor him to buy close, because poor markets force him to sell at a lowmargin of profit. He asks permission of the owner to make a systematiccruise of the area. With this permission, the dealer sends a crew intothe woods to make a closer estimate. The crew uses the strip method,measuring the merchantable trees on 10 percent of the area. Diameterreadings are taken by calipers, and local volume tables are used toconvert diameter readings to volumes in board feet.

After the systematic estimate is finished, the dealerconcludes that he can afford to pay the asked price, since his estimateis higher than that made by the first cruise. The transaction is made,and the logging operation begins. The dealer goes into the woodshimself, and with other timbermen in his employ, marks the trees to becut, being very careful to mark only the trees above the diameterminimums specified in his contract. Men are employed to fell and buckthe trees. Each sawing crew fixes its mark on the timber which it hascut. Every day or two, a log scaler employed by the dealer, scales thetimber cut by each crew and enters it on a record sheet which he turnsover to the the pay-roll clerk.

After the timber has been cut, it is snaked toskidways by contract loggers. It is unnecessary to rescale the timber asa basis for paying the skidders, because the scaler has marked the scaleof each log on its end.

Meanwhile the dealer has sold his timber to a millowner several miles away. The mill has its own equipment fortransporting the logs. They are scaled at the skidway by a competentscaler employed by the mill and the dealer himself. They agree on thescale of defective logs, sometimes having rather heated arguments as towhether a log is merchantable or is a cull.

The timber has changed ownership twice and its volumehas been estimated in board feet several times, but it is still to bemeasured many times. The mill owner, as a check on his scale and as amatter of business record, measures the exact volume of sawed timberthat he obtains from the logs.

The use of forest mensuration is apparent. Furthermeasurement of the timber would be classified as scaling lumber.







The Forest Owner Secures an Estimate.








The Prospective Buyer Makes His Estimate.








The Timber Is Sold.



Trees Are Marked for Cutting.



Regular Check Scales Are Made.






The Mill Owner Rescales the Logs.






A Mill Check Is Made.



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