SURVEYS IN THE MOUNTAINS

Press, Volume LXXIII, Issue 21989, 13 January 1937, Page 8

SURVEYS IN THE MOUNTAINS

How Work Was Done CLIMBERS NOW FILLI^; IN GAPS Although most of Canterbury hgjbeen closely and accurately . surveyed, there still remain extensive areas in the mountain region $ which the survey has consisted only in fixing the position of outstanding' peaks and other notable features of the landscape. It is this fact that gives importance to the work of the parties of climbers which every summer spend so much time in the mountains. The information . they gain is '■-gradually adding to ffe, knowledge of the mountain region, and is making possible more ate maps. i Surveying by the methods known to most people, with distances measured on the ground by a steel'tape' along lines whose bearing is \ obtained by theodolite, is not possible' in-'the mountains except at very; great expense. Consequently in, the? mountain surveys used for the eiA, isting maps of such areas as the"! Mount Cook, Upper Rangitata,.and" Rakaia regions, other methods have had to be used. As distances can-' not be measured along the they have to be arrived at by cal- • culation from bearings obtained with"

a theodolite. ->* A surveyor engaged in such wori f first of all establishes what is knofn«' as a base line. That is, ne Sm' two points whose distance apart is ■ known. Then he moves on. to hg'-:. next-observation post and observes the bearing from there of those two.known points, and also of any fea-, tures. of the landscape whose pes-' wishes to record. So .hemoves on up his mountain valley,-*' at each post taking the bearing backto his previous position and on to' the next and also of those features ■ of the landscape he observed fromhis former position, as well'as new ones. .When, this mass of criss-cross' bearings, starting from the baseline, is transferred to a plan it pro-f duces a series of interlocking- tri- l angles, the length .of the sides ofwhich can be calculated progressively from the first triangle with the base-line of known length. $-. ' Compiling the Maps . \ From such surveys as - these :the maps of the Canterbury have been produced. In theimain . the Purveyors have worked up the" valleys, taking the bearings of as they went, arid at times climb-, ing some of. the more accessible, peaks to enlarge the field of,their' observations. The positions of-the-peaks as shown on the maps, ancU the courses of rivers and glaciers,* have been arrived at by observation and calculation, and>Jlot by measurement along the ground, s. Those who have undertakerTsuch - work, however, have had*,'.-to use their eyes in other ways " besides. through the lenses of ■ a theodolite,' Their field books record bearings from one point to anojrtjtej but the nature of the versed, the position of line, and the extent of. vegeptiOa In these books also are sketches,, many of which would do credit to a professional artist, showing _ the general aspect of the country asseen from each point. From the record of bearings* together with these > notes and sketches, skilled draughty men have ultimately produceA>the ■ fine topographical maps of *.*Jge_ mountain regions which are among the most prized possessions of 'the Lands and Survey Department in Christchurch. No Contour Surveys Such a method of survey necessarily- leaves out many details. The direction of ridges not connecting main peaks, and of overhanging glaciers which cannot be seen from below; or from readily accessible points, as well as the steepness of slopes—all important matters to the mountaineer—cannot be recorded in a survey of this type., Nothing has - yet been attempted in New Zealand, like the mountain surveys' of the, Swiss, Italian, Austrian, and German'frontiers, where accuratemeas-;* urements have been taken along,contour lines at 100-foot intervals. These surveys, undertaken for miuI tary purposes, have produced contour maps which enable mountaineers to see at a glance the sort or country they will have to traverse in undertaking any climbs. In New Zealand such contour maps of mountain regions have not been attempted because there is insufficient justification for the expense and time involved. There is no military incentive, and the corn-,. mercial incentive of gold-nurung r does not exist on the Canterbury side of the Alps. The only remain- _ ing incentive—the provision <» maps for tourists and mountaineers —is not offset by any prospect 01 an adequate return for the money spent. . :« Meanwhile leading members « the - mountaineering clubs are gradually fiUing in the blanks- rn the maps of the mountains, pne" - observations have revealed err ol *' in the positions of pecks marked on existing mans, and given details 01 the position of many intermediary, peaks, glaciers, and streams, -ineu , work is done with military •P l ?', v matic compass, panoramic * graphy, and aneroid barometer x* determining approximate heign»f. ; They have gone into many are**-; not visited by the departments sin-', veyors,~fand their collaboration JM» .. been welcomed by the department- r>