PUBLIC RECORD
OFFICE
61
Reference :-
C.O. 885
20 PUBLIC RECORD OFFICE, LONDON
ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH—NOT TO
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No. 16.
FOREIGN OFFICE to COLONIAL OFFICE.
(Received 15 March, 1909.)
[Answered by No. 19.]
SIR,
Foreign Office, March 13, 1909. I AM directed by Secretary Sir E. Grey to state, for the information of the Secretary of State for the Colonies, that he has received a despatch from His Majesty's Acting Agent and Consul-General at Zanzibar on the subject of a proposed survey of Zanzibar Island,
It would appear that the Zanzibar Government, to whom a memorandum on the subject prepared by the Director of Military Operations (copy enclosed) had been submitted, are of opinion that it would be a waste of money to have a cadastral survey of the island made, in view of the fact that a map exists on a two-inch scale, drawn up from a trigonometrical survey. They also think it very doubtful whether it is desirable to make a survey which would show the boundaries of all the pro- perties, as some of these are very small and are being constantly divided. It is stated also, that land in the country districts is of not much value of itself, and is bought and sold by the number of productive trees, such as cloves and cocoanuts, which it contains, and certain of these trees are used by the natives to define their boundaries. In many cases also on the death of an owner it is not the land itself but the trees which are divided amongst the inheritors.
The Zanzibar Government are therefore of opinion that the best plan would be to mark out definitely and re-survey (1) the properties belonging to the Govern- ment; (2) the larger properties of private owners. For this purpose the Director of Public Works is of opinion that an enlargement of such sheets of the present map as are necessary should be made to a scale of either four or six inches to the mile, and that roads and villages should be shown more in detail, and areas of agricultural and waste land should be clearly defined on the present map.
As regards the Island of Pemba, as no survey has ever yet been made, and the only map in the possession of the authorities is a tracing of the Admiralty Chart, on which have been roughly shown the roads and the boundaries of districts, the Zanzibar Government deem it very desirable that a complete survey of this island should be made. They think that probably the best course would be to follow the same lines as suggested above, commencing with a survey of the whole island on a two-inch scale.
As to the question of surveyors to carry out the work, there is apparently some difficulty in obtaining the loan of officials from the Indian Government. Should none be procurable from this source, the Zanzibar Government would suggest either engaging the men in England, or, provided the work could be thoroughly depended upon without the employment of an expert to check it, entrusting the survey, under contract, to some reputable firm in England. The Indian Government, it might be stated, would be willing to supply the necessary instruments on book debit, taking them back on the completion of the survey at the valuation of the Surveyor- General of India.
Sir E. Grey communicated to the Director of Military Operations the above- mentioned observations of the Zanzibar Government, and Major-General Ewart has, in reply, stated that he can offer no opinion as regards the desirability, under the special circumstances, of showing the boundaries of all the properties, but that the proposal to enlarge the existing map is not without its obvious objections, the chief of which perhaps is that small errors on the two-inch scale become increased out of all proportion if the map is enlarged, and render it very untrustworthy.
General Ewart adds that the matter might be referred to the Colonial Survey Committee, who could, in their turn, consult, as suggested by His Majesty's Acting Agent and Consul-General at Zanzibar, the Commissioner of Works of British East Africa, who is at present on leave of absence in England.
I am accordingly to state that Sir E. Grey would be grateful, should the Earl of Crewe have no objection, if the whole question could be laid before the Colonial Survey Committee in accordance with General Ewart's suggestions.
I am, &c.,
W. LANGLEY.
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Enclosure in No. 10.
Zanzibar-Cadastral SurRVEY.
1. The object of the cadastral survey of Zanzibar being the construction of a map of the islands excluding the town area, the map should show the boundaries of all properties, should give the area of each property, and indicate the owner.
2. The character of the survey should be such that no resurvey should be required after its completion, although from time to time revision would be carried out in places where property boundaries may have altered. It is therefore necessary that an accurate framework for the map should be constructed, that the points of this framework should be permanently marked on the ground, and that the relative positions of the points should be recorded and published.
3. The data available for preparing a scheme and estimate are:-
Area of Zanzibar, 640 square miles.
Population town,56,000; rest of island, 120,000. Of this population, the
Arabs, who form the land-owning class, number about 10,000.
The chief vegetable products are cloves and cocoanuts; there are also cassava fields; and in the eastern portion, chilli patches. In size the estates vary from 2 to 60 acres, the average being about 12 acres. But there will certainly be cultivated patches as small as quarter acre.
4. The scale of the map should be the smallest which will give the required information conveniently. If two acres is taken as the lower limit of area of estates properly so-called, and if it is assumed that one-quarter square inch (half-inch square) is the smallest area on paper which can be measured conveniently, the scale which meets these conditions is 1/5000 (about 121⁄2 inches to one mile).
5. Each sheet might be two miles square (4 square miles); more than 160 sheets will be required to cover the island.
6.
Technical details.
(i) The framework should, as far as possible, be trigonometrical. The islands are 47 miles long by 20 broad, and have hills rising 450 feet, and as a good topo- graphical map exists, it should not be difficult to cover Zanzibar with a triangula- tion of which the sides should vary from three to six miles. Taking the average side as about 4 miles, about 80 main points will suffice for the whole area.
In addition to these main points, about 400 secondary and intersected points should be fixed, each of the latter by at least three intersections..
There will then, on an average, be three trigonometrical points on each sheet. All these points should be permanently marked.
(ii) No doubt in parts of the islands the vegetation and cocoanut plantations will make triangulation difficult. In such parts, it should be given up and main traverses should be substituted and the points marked.
(iii) The detail should be fixed by theodolite traverses run between points fixed
as above. These minor traverses should be cut up by simple chaining. The exact amount of each can only be decided in the country.
(iv) The standards of accuracy should be:-
(1) Bases for triangulation 1/50,000.
Main triangles, triangular error not to exceed 5 seconds.
(3) Azimuths, p. e. 2 seconds.
Chaining main traverses 1/5,000.
(5) Chaining minor traverses 1/1,000.
(6) Angles, main traverses, 10 seconds.
Angles, minor traverses, 30 seconds.
(v) The work should be taken up systematically sheet by sheet.
The diagram for the whole island should be prepared before the work is com- menced.
The triangulation and traverse points should be referred by rectangular co-ordinates to an initial meridian.
Each sheet should be strictly triangular.
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