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APPENDIX A

A SHORT SUMMARY OF, AND DISCUSSION INTO,

THE MERITS OF THE TRIANGULATION EXECUTED BY RAI SAHIB RAM SINGH AND RAI BAHADUR LAL SINGH, SURVEY OF INDIA, DURING THE THREE EXPEDITIONS OF SIR AUREL STEIN, K. C. I. E., IN CHINESE TURKISTAN

BY

MAJOR KENNETH MASON, M.C., R.E. OFFICIATING DEPUTY SUPERINTENDENT, SURVEY OF INDIA

INTRODUCTORY

The triangulation discussed below falls into nine groups, viz.,

(A)—On the Tagh-dumbash Pamir, 1900-01 (Ram Singh).

(B)—In the neighbourhood of Muz-tàgh-ata and the Little Kara-kul, 1900-01 (Rim Singh).

(C)—At Tash-malik hill, 1900-01 (Ram Singh).

(D)—Near Tash-kurghan fort, 1906-08 (Rim Singh).

(E)—South and east of Kho.tan, .1900-01 (Ram Singh).

(F)—From Achchan to Kapa, 1906-08 (Ram Singh).

(G)—In the headwaters of the Yurung-kash, 1908, (Lai Singh).

(H)—From Kapa to latitude 39° 0', longitude 89°47,' 1913-15 (Lai Singh).

( I )—From Astin-bulak to Korla, 1913-15 (Lai Singh).

It must be remembered that at the time of these operations, with the exception of one or two points on the K'un-lun mountains south of Khotan, no inter-Basis of triangulation. sected points, from which the observers could resect their position, had been rigorously fixed by the Survey of India; and that therefore the relative accuracy and value of the triangulation are dependent on the merits of Capt. Deasy's work, on which it is largely based.

On the Pamirs there existed a few points fixed by Colonel Wauhope during the Pamir Boundary Commission of 1895, but they alone were insufficient for the needs of R. S. Ram Singh at any one of his stations.

Deasy's and Wauhope's work were both connected indirectly by resection to unmarked peaks fixed by the Survey of India. Neither of these observers could be certain that he

resected his own positions from the exact points observed by the Survey Sources of possible error triangulatirs, and Ram Singh and Lai Singh must have been in doubt

as to the exact summits, fixed by Deasy and Wauhope, from which they resected their own stations. In many cases the peaks employed had been intersected from long distances by badly formed triangles and were themselves liable to some error.

Wauhope's work is known to have been accurate within a very few seconds, and the regular work of Deasy is also good. Nevertheless, in many cases, the stations of the latter have been fixed by observed latitudes and azimuths to distant peaks, determined previously by himself or Wauhope, and the intersection of the azimuthal ray and the latitude parallel has been very acute, thereby introducing a further error.