PUBLIC RECORD OFFICE
Reference :-
C.O. 885
ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH—NOT TO
20 PUBLIC RECORD OFFICE, LONDON
State of the Map.
Base of Survey.
Triangula- tion.
Levels.
Method of
executing Topo-
graphical Survey.
Rate of Survey.
L
(b) Cadastral. To supply the Government with township and other plans
required.
с
2. TOPOGRAPHICAL WORK.
(a.) The Colony of Southern Nigeria is covered by 87 sheets of the 1/125,000 map of Africa. Of these sheets, 34 cover only portions of the Colony, and for the purpose of calculating the time required to complete the survey, it may be reckoned that 64 complete sheets will require survey and production.
Of these 64 sheets, six have been recently produced by Messrs. W. & A. K. Johnston from the work of the Survey Department. It is clear that these sheets require such complete revision that a re-survey will have to be made, though there is no doubt that much of the old work can be retained for the sake of economy.
(b.) Before any country can be topographically surveyed, a horizontal and vertical framework on which to base the map must be laid down. Practically the only horizontal framework existing in the Colony consists of certain traverses in the Western Province executed by the Survey Department. Until I have made a personal examination of the technical nature of this framework I can form no complete idea of its value, but at present it seems probable that it will be sufficient for the base of about nine of the more southern sheets of the Western Province.
(c.) The other sheets must be based on a framework constructed by triangula- tion, which combines both vertical and horizontal framework. This triangulation must gradually be extended across the northern portion of the whole Colony until it reaches the Kamerun boundary, the horizontal and vertical framework so formed being extended to the south, either by triangulation (where possible) or by traverses.
(d) The vertical framework in the Western Province at present only consists of the railway levels, and whether I can accept these or not future investigation will reveal. A special party must be at once put on levelling work to form a vertical framework in the southern portion of the Western Province (and afterwards of the Colony generally) until it reaches the area covered by the proposed triangula- tion.
(e.) Field parties, each consisting of one European and one native surveyor, and working in pairs, will be sent into the field between the 1st September and the 1st May-eight months. Each party will be given a definite area to survey and will field" sheet of the map covering be responsible for the complete execution of the that area.
Owing to the absence of a sufficient framework in the north of the Western Province, the southern sheets will be started first, and the work will gradually extend northwards over the triangulation which will in the meantime have been executed, until the whole of the Western Province is completed, when it will follow the triangulation eastwards.
At the end of the field season each party will bring in its field sheet completed, a tracing will be made in the Topographical Office, and the resulting material for the production of the map forwarded to England.
(f.) In calculating the rate of progress of the topographical survey I have based my figures on experience of such work in the open country of South Africa and the dense forest country of the Gold Coast. In computing these rates due allowance has been made for work already executed and the present lack of know- ledge of the staff in plane-table work and contouring, a lack of knowledge which will gradually cease to exist.
Rate I. In forest and jungle country.near the coast line and around the lower reaches of the big rivers. 11 months per sheet.
Rate II. In the more open country, broken by patches of forest. 9 months per sheet.
Rate III. In the open hilly country in the north and east of the Colony. 7 months per sheet.
79
At these rates of work, the progress made in producing the map will be as follows:-
let
2nd
3rd
4th
5th
6th
7th
Xth
9th
10th
Ilth
12th 13th
14th
15th
16th
17th
15th
19th
20th
21st
22nd
23rd
24th
25th
26th
Under proposed Leave Conditions:- 8 months Coast,
4 months away.
With proposed Staff,
Under proposed Leave Conditions (see para. 4 (3), (0).
Remarke.
With present Staff.
Year.
Under Existing Leave Conditions:--- 1 year on Comet,
6 months away.
Sheets.
Sheets.
Sheets.
24
3
5+
Forest
24
32
-64-
21
·3·
6.4
22 44
61
country. Western Province completed.
Open country be-
Western
gun, Province. Western Province
completed after
10, 6, 31 years respectively.
7
7
7
7
Survey of Colony
8
completed alter
20, 17, and
9
61
years
respec-
tively.
No allowance is made
for illness.
For proposed Leave Arrangements see paragraph 2 (g).
(g.) In studying the foregoing estimate of progress, the disadvantage attendant Leave con- on the present system of leave is obvious. The best time of year for topographical ditions work in the field is from about September to about the end of April. The four and Sur- wet months, May to August, may occasionally permit of survey work in the field, Vey Season. but are not to be depended on. Topographical work in the rains is costly work, as the surveyor cannot go out on rainy days and his carriers are consequently idle; if he does go out he is liable to fever after getting wet, and he loses days in that way. The physical disadvantages of working in the wet also are against good results, and many delays ensue through swollen rivers, heavy roads, &c.
By the system of work adopted all sheets will be finished in the field, so if the surveyors come in to headquarters during the rainy season there will be no topographical work for them to do. The leave of some under the present system may be due then with advantage, but in the majority of cases the leave of the surveyors overlaps and extends over portions of the dry season, so that often not more than two or three of the present staff are available for work in the field at the best time of year.
I recommend that the whole of the Topographical Staff should go on leave for a period of four months from the Coast (including voyages) on the 1st May each year.
Precedents for this course exist, I believe, in the Harbour Work officials on the West Coast. They exist in the Gold Coast Survey, and in India it is a thoroughly recognised fact (which is acted on) that no surveyor is fit for more than about six months' work in the field, spending the remainder of the year in the office