PUBLIC RECORD OFFICE
[། ། ། ། །
C.O.
Reference :-
885
20 PUBLIC RECORD OFFICE, LONDON
ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH-NOT TO
104
No difficulty was experienced in the photographic part of the work. Exposure was estimated by actinometer, the two plates of a pair being given the same equi- valent exposure, and developed by time in tanks on the same day as the exposure was made.
Much of the work was hindered by bush fires. Some days it was useless to make exposures and on about 40 per cent. of the plates the finer detail in the distance is obscured.
The angle subtended by the sub-tense bar was measured with great precision by a 5-inch theodolite. Since the angle was small, the method of repetition could be employed with a factor of 10, yet within the range of the tangent screws, thus obviating the errors of clamping and unclamping. Four repetition sets were made on different arcs of the limb, and the results give a probable error averaging ±0.2 ± 1 in 10,000. On a 200 yard stereo base, the total probable error was 1 in 5,000, including all errors save the standardization of the tape used for measuring the bar length. Plotting and Plotting was commenced at Nanukuloa on the arrival of the stereo-plotter ou March 1. In order to permit of a direct reduction to the new international scales, the map is being plotted to 1:31,250, the contours being directly plotted to 100 feet and sketched in from observations to 50 feet. It has been considered best to plot the map in the first instance as if curvature did not exist; the heights of the contours can be afterwards corrected by drawing a series of circles round the stereo station showing the distances corresponding to corrections increasing, say, by 10 feet.
scale.
Errors.
Work in the
coming
sensun.
It is very difficult to evaluate the numerous sources of error in the camera and plotter, but the first plots indicate that the position of the independent control point is fixed by the instruments with considerable precision, provided that reason- able attention has been devoted to the adjustments both of camera and plotter. The accuracy is apparently in the neighbourhood of the limits of plotting on the scale of 2 inches 1 mile, say 1 in 400. It would seem then that the map would be nearly correct in plano to the limits of plotting, but there is greater uncertainty in the altitudes. With a control point, however, almost all the errors should be capable of adjustment over the whole range of the plate, excepting the varying effect of curvature and refraction on altitude. It would appear that there is room for improvement in the mechanical arrangements for altitude, which cannot be scaled off to a closer amount than 20 feet.
It is anticipated that more time will be available for topographic work in the present year.
X. Health. The health of the staff and porters has been good. One native died in hospital from dysentery and two were invalided home convalescent.
G. T. MCCAW,
Nanukuloa,
March 25, 1911.
25561
Officer in Charge, Trigonometrical Survey.
No. 53. UGANDA.
THE GOVERNOR to THE SECRETARY OF STATE. (Received August 4, 1911.)
Government House, 11th July, 1911.
(No. 197.) SIR,
I HAVE the honour to acknowledge the receipt of your despatch, No. 134, of the 17th April,* on the subject of the employment of non-official licensed surveyors. and to inform you that permission has accordingly been given to Messrs. Mayne and Seth-Smith to undertake definite surveys.
2. The proposals contained in paragraph 3 of your despatch under acknow ledgment certainly afford a temporary solution of the difficulty, but I do not think that the arrangement can be considered wholly satisfactory so far as it concerns the survey of native properties. In this opinion I am guided by the Director of Surveys' memorandum, dated the 18th February, 1911, a copy of which was enclosed in my despatch, No. 71, of the 21st February last.†
• No. 51.
† No. 50.
105
3. However,, except by the appointinent of another Crown Lands Surveyor, I am unable to propose any more satisfactory method of dealing with any unex- pected increase of survey work..
I have, &c.,
30828
No. 54.
F. J. JACKSON,
Governor.
MINUTES OF MEETING OF THE COLONIAL SURVEY COMMITTEE, 19TH SEPTEMBER, 1911.
1.
PRESENT:
Mr. READ (in the Chair).
Colonel CLOSE.
Major GORDON.
Mr. PARKINSON (Acting Secretary).
A letter from Mr. Townsend on the subject of the vacancies for computers in the East Africa Protectorate was read. In spite of Mr. Townsend's criticisms, Colonel Close maintained that Mr. Adamson would be suitable for the post of com- puter. While having no great mathematical knowledge, he is able to undertake all ordinary survey calculations, and could certainly learn, if necessary, how to calculate areas by the co-ordinate method. He has taught all the non-commissioned officers at Chatham, and he has at times taken officers' classes in, practical astronomy. It was decided that Mr. Adamson should be recommended for the post of second computer, and that if possible a superior man should be obtained for the post of first computer. Colonel Close promised to look into the matter and see if he could find a suitable man at Southampton.
2. It was decided provisionally to arrange the meeting with the Governor of Ceylon to discuss the Ceylon surveys for Friday, 27th October, at 12 noon.
3. A letter from Colonel Jackson on the subject of the relative merits of the metrical and the " inch-mile" scales for survey maps in the Federated Malay States was discussed. In view of the fact that the Indian Government still adheres to the latter, the Committee considered that the " inch-mile " scale should be retained in the Federated Malay States.
4. The Committee considered a letter from the Institution of Municipal and County Engineers asking for recognition in connection with the examinations held for Colonial survey appointments. It was decided to recommend that the examina- tion of the Institution should be accepted as exempting a candidate from the technical, but not from the mathematical, test.
It
5. The Committee considered a letter from the Secretary of the Board of Geographical Studies, Cambridge, enquiring whether candidates who have obtained the University diploma in surveying could be exempted from the technical test. was recommended that candidates holding the diploma should be exempted from the technical test but not from the mathematical test, unless the University make a further application, when the matter should be reconsidered.
6. The Committee supported the allocation of Mr. Coates and Mr. Weston to the East Africa Protectorate Survey Department (cadastral branch).
7. A memorandum on the proposed reconnaissance survey of British Honduras was read (copy annexed). The Committee accepted the method of procedure and estimate as set forth in the memorandum, but considered that a subaltern, Royal Engineers, should be substituted for the ex-non-commissioned officer, Royal Engineers, proposed in paragraph 6.
Major Gordon explained, with reference to the list of instruments in para- graph 6, that since the preparation of the memorandum, the instruments there enumerated had been taken over for other work, and therefore would not be available. 8. The finished sheets of the Uganda survey (1/250,000) were shown, Entebbe and Hoima being the only sheets outstanding. It was recommended that an effort. should be made to get forward with work in the two untouched squares, viz., Fort Portal and Ankole. Major Gordon undertook to submit an estimate, allowing for a reduced party which would consist probably of two officers and four non-commis- sioned officers.