SURVEY ON THE MOUNT EVEREST RECONNAISSANCE, 1935

MICHAEL SPENDER

Readers of the Himalayan Journal have already been informed by .two articles in vol. vii, 1935, of the merits of photogrammetry. No other method, it was then implied, could prepare the kind of map which the scientist or geographer nowadays demands. Moreover, an ever increasing number of mountaineers are beginning to expect that any much discussed mountain should be illustrated with that type of excellently contoured map which a photographic survey immediately supplies.

The Royal Geographical Society were, then, understandably anxious to take advantage of the opportunity of Mr. Shipton's Reconnaissance Expedition to secure a photogrammetric map of Mount Everest.¹ Since the expedition itself only came into being a few weeks before it left England at the end of April 1935, time was very short for the business of getting the equipment together. I had something like three weeks in which to collect instruments and pack them; without the valuable help of several firms I should never have been able to get to Tibet at all.

It would be misleading to suggest that we travelled to India in any particularly optimistic mood. The expedition was to take place during the period of the monsoon, and though other expeditions have found conditions tolerable, or even good, in other parts of the Himalaya at the same time of the year, it was certainly true that the Reconnaissance Expedition of 1921 had had a difficult, even bad, time on account of cloud and snow. Nevertheless, that expedition came back with a fine show of results, of which the map made by Major Wheeler was by no means the least important. That map, too, was made by photographic survey, and was of a quality which meant that we must exert ourselves to improve on it. On that earlier survey stereo-photogrammetric survey was not employed: instead of a pair of photographs taken at the ends of a base, single photographs were made. Instead of plotting contours from the two photographs from one base, points were plotted from a pair of the single photographs from different stations which covered the same piece of country. This method is in reality a kind of plane-tabling, with the advantage of quick field-work; but it has been generally discarded, except for very particular occasions, because the difficulty of identifying the same point on photographs from quite different stations is so great that plotting becomes a tiresome business. The method has nevertheless again been employed by the Survey of India this summer (1936) in the Nanda Devi basin. Moreover, the plastic, three- dimensional impression of the country, which the stereo-photogram- metric method retains and which the skilled plane-tabler forms in his mind, is lost in this treatment of single photographs.

 

There is perhaps still a field for this method of survey which, in spite of its disadvantages, has given maps of the Canadian Rockies as well as of the Mount Everest region. Mountaineers go by nature to the very kind of points which would make good stations for this type of survey. Once there they might sometimes be persuaded to supplement the regular surveyor's work with calibrated pictures round the horizon from such a point. This at any rate was in our minds when Mr. Hinks and I worked out an arrangement to mount a Leica miniature camera on to a light Watts mountain theodolite.¹ It was to be the very extreme of portability and simplicity, since it seemed unwise to make too great demands on the mountaineers who might use it. As soon as we had started I was surprised and gratified at the extent to which the mountaineers were interested in the survey. Theodolite classes were held in the well-decks during the passage across the Indian Ocean: they were well attended, and when we came to the field the leader and two members of the party, Warren and Kempson, began to show an interest and enthusiasm for map-making which not only endured the summer but constantly expressed itself in taking the instrument to the kind of peaks which I should never have reached.

My own apparatus was really in duplicate. At the R.G.S. was the Wild photo-theodolite which Major Mason had used in the Shaksgam in 1926. As it stood, the equipment was rather heavier than that which had been developed subsequently by the Danish Geodetic Institute for use in Greenland. There we had used a Wild theodolite for the angular observations and a Zeiss camera designed to take roll- film for the photographs. Through the great kindness of the Director, Professor Norlund, the camera and tripods were lent by the Danish Geodetic Institute. The Survey of India lent a Wild theodolite and a new specially light subtense bar by Wild with which to measure the lengths of the bases. In this way I was sure of being able to carry the apparatus to fairly inaccessible stations. But for the survey of Mount Everest itself and of the Rongbuk valley I took the standard Wild equipment, partly for the purpose of investigating its usefulness and deciding how it might be modified or lightened for exploratory work.

 

After a short halt in the neighbourhood of the range containing Nyonno Ri and Sangkai Ri, Rongbuk was reached on the 4th July 1935. It was just at the end of a period of bad weather at the beginning of the monsoon, which the local inhabitants might perhaps have designated the chhoti barsat. The days immediately following were fine, and while we spent the time doing unavoidable repackings and observances at Rongbuk, Mount Everest and the other peaks gleamed white with new snow in a cloudless blue sky.

On the second day we left, and I began the survey of the Rongbuk valley on my own, assisted by Tewang and Ang Tsering. Stations were made on each side of the valley from the Base Camp. To reach the western stations the glacier stream had to be forded before dawn. This was possible, but this and similar passages through apparently super-cooled water I reckon as by far the most unpleasant feature of Himalayan travel. Before going farther up towards Mount Everest I made some stations in the little valley lying to the east of the Base Camp, which was very poorly mapped. Then I followed with some stations near Camp I before joining the party which had been climbing, in the meanwhile, to the North Col from Camp III.

As soon as the mountaineers were clear about the fact that any further climbing from the North Col would be impossible, they split into parties, to one of which I became attached. Kempson, Warren, and I made a tour up the glacier which branches from the East Rongbuk glacier towards Kharta Ghangri. They climbed various peaks including Kharta Ghangri (23,070 feet) itself. The last camp was beyond the watershed, at a place called 'Spitsbergen Camp', where there is a lake at an ice-cliff. This is bounding a sheet of ice in many ways like an Arctic ice-cap. Here, for some obscure reason, I became ill with some complaint resembling mild dysentery. At the same time supplies began to run short; two of the Sherpas did a splendid journey down to the village at the Kharta side and back, after which we retired to the Base Camp.

There followed a visit to Camp II before the whole party reassembled for a journey to the country round the Survey of India's peak 22,150 which we called the ^cDent Blanche'. Here we came to the margins of the existing survey and there was every reason to get as much mapping done as possible: the quarter-inch map was so vague that actually we had some difficulty in identifying the valley we had come into, that of the Lang Chu, after crossing several passes.

We had hoped at the time to do further useful work that summer, but it became inadvisable to make a second visit to the Nyonno Ri, and even a survey on the Sikkim border had to be given up because the monsoon was still persistent.

The results are still being worked out. The plotting of the stereo- photogrammetric work is held up for lack of available apparatus; but the network of triangulation can be calculated and drawn. This has not been as simple as it might have been because of the variable reliability of the points in the existing triangulation. Some were up to half a mile out of position, others less; to find out exactly which points were reliable was a tedious business, which often meant making the complete plot afresh.

Some interesting results are being obtained by attempting to combine the results from this expedition with the photographs from the Houston Everest Expedition in 1933.¹ The aeroplanes making these fine flights carried several cameras, but unfortunately the calibrated cameras were only used for vertical photography. The relative height of photography being so small, the vertical photographs showed only a very narrow strip of country. The obliques, which would ordinarily have been very suitable for making a map of this country, were taken with uncalibrated cameras. This means that the position of the lens is uncertain with regard to the photograph, so that any precise map-making is impossible. However, the ground-photographs have been used to obtain a number of heights in the region near Mount Everest, Makalu, and Ghamlang. Some success is being attained in using Captain Crone's method for obtaining heights of other detail.

Although making a stereo-photogrammetric survey in these parts was a fairly weighty event from a geographical point of view, possibly the most important result of the expedition was to introduce the climbers, people like Shipton, Kempson, and Warren, to the methods of photographic survey. An experienced traveller never likes leaving a badly mapped country without improving the existing map: mountaineers, possibly more than most travellers, think in terms of the map and visualize country in front of them as a map in a way which is otherwise only the habit of the plane-table surveyor; so that, given a suitable technique, mountaineers show themselves at once as ready pupils and very soon as skilled geographers. The little instrument, the Watts-Leica photo-theodolite which, complete with stand and camera, weighs less than 20 lb., was taken up with enthusiasm and has indeed spent the current (1936) summer again in the Himalaya, so that there has been no time to modify the construction or do any thorough testing. From preliminary tests, however, it would seem that horizontal angles can be taken out with all the accuracy necessary for graphical plotting, and probably the vertical angles would give adequately accurate heights up to medium distances from the instrument.

 

The vast tracts of the Himalaya which still remain to be surveyed will probably be mapped from photographs. In other parts of the world, in Switzerland and in Austria in particular, mountaineers have played an important part in insisting on the proper representation of the fields of their achievements. The Deutsch-Osterreich- ischer Alpine Club has indeed set its own surveys into motion and caused them to be published, as witness the map of the Gross- Glockner. It is to be hoped that Himalayan mountaineers will be equally insistent and see to it that in Britain just as adequate facilities are established for the working out of photographic surveys.

Postscript

The map of the North Face of Mount Everest, published with this Journal (p. 126), has been drawn by Mr. Milne of the Royal Geographical Society's drawing-office. The expedition of 1935 provided the photographs, which, together with the contours plotted on Professor Norlund's instrument in Copenhagen, formed the basis of the compilation. Photographs from other expeditions have also been used, notably those exposed in Major Wheeler's photo-theodolite during the Reconnaissance of 1921. The additional points necessary for a map on this scale were obtained by intersections from the several photographs. The elegance of the result is a tribute to the care with which Mr. Milne has carried out the various graphical constructions and his skill in interpreting photographs taken in widely diverse conditions.

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