University of Idaho School of Forestry - Forester Yearbook (Moscow, ID)

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THE IDAHO FORESTER 43 fortless minutes and conclusions are reached that are qualified by few mental reservations! The flights, both reconnaissance, photo- graphic and reflights for the Lewis and Clark Highway, were completed in twelve hours of fiying time and about 1,000 miles were flown. A ground party would occupy that period in traveling ten miles along the trail and mak- ing camp. The films were sent to Washing- ton, D. C. by airmail for development and printing. In ten days from the date of taking, the pictures were received and the stereoscopic study began. From the air, the alternate routes are con- sidered close together and no term of time or effort lies between the observations to dull the impression derived, as is the case when travel- ing laboriously along faint trails upon the ground. When observed information is sup- ported and supplemented by continuous photo- graphs, the aerial method far outstrips ground reconnaissance in every respect. In addition, the resulting record is of much greater value, due to its increased scope and versatility of use. It is, in fact, visual proof of the condi- tions, while that of ground reconnaissance is simply verbal and subject to the personal equation. PRELIMINARY ESTIMATE After the photographs of the various routes have been studied under a stereoscope and a tentative route has been indicated upon the mosaics, the pictures are again studied and a preliminary cost estimate is made. This preliminary or reconnaissance estimate is made just as it would be by a man upon the ground. The ground conditions show clearly under the stereoscope. Some distortion occurs in the steepness of the slopes due to variation in the overlap of the pictures, but the same condition obtains on all the routes so the result balances suhiiciently for comparison purposes. Stream crossings are more readily determi- nate upon the pictures than upon the ground. Advantageous breaks in the slopes above the rivers are located at once and not passed by as when traveling below. The choice of ground along the main streams is readily made as the pictures show half a mile on each side. Cliffs and slopes are easily distinguishable, particu- larly in open country, and large boulders in the rivers are discernible. BEST ROUTE READILY ASCERTAINED When the line leaves the rivers and supports along the slope, the procedure does not con- tinue with as much confidence as along the river as there is no gauge of elevation except by estimating the height of the trees and step- ping off the ascent or descent accordingly. The character of the country shows, however, and the gross ascent is usually known, so the distance across each type of ground is de- terminate and the cost is estimated. The pur- pose at this time is to arrive at comparative costs and so know the relative value of alter- nate routes. With these figures are placed the physical values of rise and fall, curvature and distance, together with climatic, political, maintenance, and economic values, the most suitable route becomes evident. To the engineer making a ground recon- naissance in heavy country, the matter of dis- tance is usually approximated, but on the air pictures that difficulty does not appear, as they can be measured on the photograph and the mosaic. ' In making these approximate reconnaissance estimates, the ground method has the advan- tage in a more detailed classification of the material. It contains, however, the more seri- ous possibility of overlooking the opportuni- ties of more favorable ground that is plainly evident from the air. Estimates of this type are visual approximations based on previous knowledge of similar conditions and little variation in judgment should occur. GROUND CONTROL The completion of the reconnaissance Hights and the photography concludes one complete section of aerial work. The choice of routes has been made and the remainder of the work re- quired is the making of a topographic map of the accepted route and the actual staking of the located line upon the ground and final esti- mating of cost. From this point, then, two courses are open. The topographic map can be made from the photographs after a ground control has been placed, or it can be made from measure- ments taken on the ground after a staked preliminary line has been established. The desired end is to obtain topography and tie it into a base line. This is required in order that the center line when projected upon the topography may be transferred to the ground in the same relation to the base or preliminary line that it occupies upon the map. Ground control consists of elevations on certain dis- tinguishable points at random on the picture and also the length and bearings of the courses between the points. This information may be secured by stadia or otherwise as the condi- tions warrant. A preliminary line would be a precise staked line close to the position that the highway was expected to occupy and form the base from which the topography would be taken and from which the projected center line would be located upon the ground. GROUND CONTROL IMPORTANT In mountain country such as that under consideration the preparations for doing either would be similar. The size of the party for ground control was less on the Lochsa than would have been the case for a preliminary line and the time taken for the fifty miles of canyon was less. Survey points upon the

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42 more than a photographic flight, but with the qualification in each case, that ground trips do not aHord the advantages previously enumerated. ' It appears, then, that up to the point of actual maps and surveys, aerial methods offer a great advantage not only in time, but in returns from the cost, and further, that there is a credit balance to carry over and apply on the cost of ground control and mapping. AERIAL RECONNAISSANCE The effectiveness of the reconnaissance and photographic flights on the Lewis and Clark project over that of ground reconnaissance was evidenced in many ways. On the Hrst flight the Bitter Root Mountains were crossed over the Lochsa River Route and recrossed over the North Fork Route. The Ridge Route lying between the above mentioned routes was observed at the same time. The flying time was three hours, over diiiicult mountain coun- try, and the distance flown, about three hun- dred miles. The main streams were in deep narrow recesses and the high ground was sharp and ragged in form. The flight was made at an elevation of from 1,000 to 5,000 feet above the ground. The highest elevation reached was 10,000 feet and in only one case did the plane descend within a few hundred feet of the ground. It was naturally supposed that the general course and relation of the routes as well as the drainage systems would show clearly, but a surprising amount of detail proved to be ascertainable at the same time. The plane was held to one side of the objective rather than immediately above it in order to permit of the ground view in perspective. STREAMS SHOW PLAINLY In the burned areas, ground details showed with a great clearness and the nature of the material was evident. On fully timbered sec- tions where the trees rose tier on tier from narrow bottoms, and the river seemed to fill the channel, the details were not so readily ascertained. In this case, judgment could be rendered only from the general steepness of the side slopes, the bald rocky spots and masses of rock that had rolled into the river. The general configuration, however, was readily observed. The heavily timbered sec- tions were not extensive in the canyons and offered little interruption. The various routes flowed by with such rapidity that the outstanding differences were presented with emphasis and comparisons were readily made. Secondary streams could, in many cases, be seen from their sources to their mouths. The side of the main rivers having the least tributary streams was easily selected. The requirements for bridges were evident. The varied characters of ground along the river bank were easily segregated. Slopes and cliffs and the main trails showed THE IDAHO FORESTER clearly, as well as fluffs of dust stirred by a plodding pack train, with which, perchance, there traveled some engineer on ground re- connaissance. The position of the pack train indicated to a certain degree the nature of the ground near the river by its occupancy or its avoidance. TREES lVlARK HIGH WATER In many cases a line of isolated trees stood at highwater line along the rivers and so showed that the area between them and the water was a bar, and not tenable. Steep sections of the main streams were in- dicated by narrow channels and white water, and slack sections by Wide channels and black water. The scars of snow slides and cloud bursts led down the slopes to fantails of debris on the river bank and bars in the stream. The entire panorama lay spread beneath in all its detail and close or distant observation was accomplished by a word to the pilot. Mountains led away on both sides and wide deflections in the courses of river and streams were seen in their true relations and in some cases invited cut-offs by the use of more ascent and descent. The top of the divide was viewed for many miles and the passes lay spread out for observation. There is slight likelihood of missing a hidden pass from the air. Out from the divide ran slopes and ridges of varied ground which told much of their texture by their form. Basins were viewed from all sides and peaks are circled with celerity. A remark to the pilot, and distant ground is quickly close by and then swept away as ,questions are answered visually. An effortless investiga- tion conducted by a seemingly detached intel- lect that requires no endurance for its trans- portation. ROUTES EASILY COMPARED FROM AIR The examination of routes lying reasonably close to main streams is comparatively simple as the actual position of the line is determinate within narrow limits. The position of a sup- ported line that may loop about is not so readily decided upon from the air as a wide area may be occupied and the elevation line can not be determined. In such cases, the ex- amination becomes more general. The con- figuration and formation of the country over which a descent is proposed, is open to con- sideration as a whole. Desirable ground for development or support is much more readily located from the air, although ground work would be required to prove its utility and co- incidence with the desired grade line. In any case, the general character of sup- porting ground on any route or routes is readily open to comparison. Aerial recon- naissance eliminates that ever present fear on ground work of overlooking something by not knowing what lies just beyond one more hill. From the air, the entire area and many miles on each side are examined in a few ef-

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44 THE IDAHO FORESTER ground control were not established perman- ently and there is no prospect of utilizing the topography in detail when the final location is made. The question at once arises as to how ex- tensive the ground control should be. The results obtained on the Lochsa would seem to indicate that they should either be more than was used or less. If the ground control had been placed in the form of a preliminary and have had the points well established, the projected line could have been located without the necessity of additional preliminary or topographic work. If less work had been placed upon the ground control by using existing maps and ele- vations and building up a map that would ad- mittedly contain some variations in course and elevation, the map in that case would have had about the same preliminary value and the field control would have cost nothing. As the matter stands now, there is no ready manner by which to place the paper projection on the ground as a located line. When the line is located, a preliminary line and a working strip of topography, as well as a new projec- tion of the line, will be required. The present work and map, therefore, is limited to pre- liminary and general purposes. Two PHASES OF TWORK This situation is no reflection upon the aerial surveys but the recitation of a result due to occupying an intermediate position. This develops the fact that aerial mapping and topography divides itself into two classes. One class for preliminary estimate purposes and one for final detail work. These two classes vary in value in proportion to the scale of the map, and the accuracy, class and permanency of the ground control. The cost varies in a similar ratio and their desirability in propor- tion to their cost as compared to that of the usual ground survey costs when supplemented by aerial photographs. SCALE or MAP VARIES WITH COUNTRY The Lochsa River aerial map was made on a scale of 500 feet to the inch and the contour interval was ten feet. For a country as difli- cult as that through which the river passes, that scale is too small to permit the projecting of a close final line. A final ground map to a scale of one hundred feet to the inch will be required over the strip that will be occupied by the highway, This aerial map then falls within the preliminary class and as such, the necessity for refinements in the quality of the ground control were not vitally essential, and could have been heavily curtailed without af- fecting the net value of the projection and estimate made upon the map. The quality of the ground control should Nora: Mr. G. E. McKelvey is Commissioner of Public Evorlisl zrncl Mr. J. H. Steuimer is Director of Highways or r a io. vary in proportion to the scale of the map. The scale of the map should vary in propor- tion to the roughness of the country. The price of the map can equal the price of a ground preliminary and topography on one line plus a reasonable amount for the increased scope of the information. The aerial map, however, has an outstand- ing advantage in utility over the ground map by reason of its greater scope and detail. In addition, increased width in the topography to include both sides and the slopes above a river does not increase the cost proportionally for the reason that no additional flying is re- quired and little more ground control. On ground surveys, additional preliminary and base lines would be required for expansion of the area and for alternate propositions. The ground map usually covers a limited strip. The suiiiciency of this strip is determined by the individual upon the ground and there is little opportunity to study alternatives and to guard against oversights. The flexibility and completeness of aerial survey information, its diversity of use and the ready expansion of topographic area, makes it a more positive and complete source of understanding than the usual ground methods. The enhanced value of the results and the safeguards in judgment that it affords makes it a better dollar for dollar investment and justifies a greater gross expenditure than ground work because it is very evident that the ultimate net economic cost will be less. Appreciation The editorial staff of The IDAHO FORESTER is grateful to the contributors for their part in the publication of this issue. The staff also acknowledges the co-operation of several agen- cies in supplying certain cuts. The University of Idaho Publicity Department supplied the cut appearing on page 41. The Caxton Printers, Ltd., Caldwell, Idaho, publishers of this year's edition, furnished the cuts on pages 1, 2, and 6, and supplied the art work for the hand lettered heading of The IDAHO FORESTER appearing on page 3. Time Flies A green fire fighter was aroused from his slumbers at 3:00 a. m. to begin the day's rou- tine. Getting ready for breakfast he was heard to say, It sure doesn't take long to spend a night in this country. During his youth he was a knotty problem, but his father was a lumberman, therefore he was a chip off the old block.