SCIENCE AND INDUSTRY. 
From what has been done before in the way of contouring by means 
of horizontal photos. only, there seems little doubt that with the aid of 
vertical and oblique photos., which are now so easily obtainable, it would 
be possible to pick out very small differences in level. (I may inter- - 
polate here that this aspect is a more or less new one to me. My experi- 
ence, in common with that of other pilots, is that at any height over 
about 2,000 feet the country below, whatever its nature, all looks flat, 
though with experience one can usually pick up hills and valleys when 
‘the sun is shining, especially if it is rather low in the sky. I am, of 
.course, aware, however, that an aerial photo, will show up many things 
that are indistinguishable to the naked eye, and Mr. Melbourne states 
that by using the Bridges-Lu-Photo theodolite an accuracy of 1 foot 
vertical in 10 chains horizontal can be relied upon.) 
After outlining the advantages of the method for such purposes as 
selecting a reservoir site or carrying out the preliminary surveys for rail- 
ways, Mr. Melbourne continues:—A Government surveyor on subdi- 
visional work spends, perhaps, a week in making a preliminary sketch 
of anew parish. Later on he or his assistant spends anything up to three 
weeks on sketching in intermediate details, such as belts of timber, open 
plains, tracks, hill features, &¢e., with questionable accuracy, and often 
loses time on road-running through not having a thorough knowledge 
of the’ country he is dealing with; whereas one flight in an aeroplane 
gives him a complete map to work on, of an accuracy second only to 
his theodolite. Having a photo.-map of the parish would not only lessen 
the amount of work, but would make the EAMLNR of road routes much 
easier and more systematic, and, in fact, enable the surveyor to classify 
the land and say with certainty where his roads can go within a week 
or so of commencing work. The old-fashioned system of laboriously 
sketching in pastoral and Crown land areas by means of the compass 
ean be done away with immediately, for just as good photos. can be 
taken of out-back runs as of the city and suburbs. Aerial photos. would 
be invaluable to the valuator, whether on pastoral work or on repur- 
chased land, in determining the exact areas of clearings, scrub, or stony 
country, swamp lands, or cultivation, all of which show differently on 
an aerial photo. The lengths of fences, drains, &c., would also be shown, 
and would enable such improvement to be valued on inspection without 
having to do any measuring up. Aerial photos. could also be used for 
keeping records, such as the extent of damage done by bush fires. The cost 
of the actual photography would not be more than a few pence per mile 
after the initial outlay, and this outlay should be saved over and over 
again on the subsequent theodolite survey. 
In considering the application of aerial photography to survey work 
along the lines suggested by Mr. Melbourne, it is undoubted that the 
methods proposed would be of great value in the rapid preparation of 
maps and plans of large forest areas, especially with regard to the pre- 
liminary work necessary for the construction of forest working plants. 
To a great extent the work of dividing the larger areas into suitable 
blocks or compartments, of framing the network of roads and rides 
necessary for transport purposes, and of planning a system of breaks 
to check destructive fires, has yet to be carried out in our forests, and 
maps made by so rapid and accurate a process as aerial photography 
would be an invaluable aid. They would not, of course, indicate the 
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