PHOTOGRAMMETRIA Large Scale Photogrammetry and Economy of Precision

Photogrammetry in Switzerland by A. Pas~orelli, Surveying Engineer, Lugano, Switzerland.

Lecture held on the occasion of the conference of the S IP at Gunten 1954

It is almost twenty years now since I f i rs t had the opportunity to get acquainted with photogrammetry when doing post~-graduate work at the Swiss Federal Insti tute of Technology at Zfirich under the guidance of Professors Dr. h.c. Baeschlin and Dr. Zeller. And for 10 years now I am at the head of a private photogrammetric organisation.

I t may be interest ing to look a bit closer into the activity and working methods of Swiss photogrammetris ts as compared to world photogrammetry and with special consi- deration of large scale and precision photogrammetry. I shall limit this expos~ to the activity within our country and to the Swiss economy. I shall not include possible jobs for foreign countries since the general rules of international photogrammetric publicity have to be applied to these.

It would also carry too far to talk about the foundation of large mapping organisa- tions, about publicity and competition on the photogrammetric world market, about "map, making factories" and aerial tr iangulation or extensive surveying. I shall consider my task as fulfilled if the following expos~ were to prove that: 1. many problems and headaches which worry large organisations have also to be solved

by small or medium sized outfits; 2. problems which may interest the whole photogrammetric world may be solved in the

unassuming premises of a small organisation; 3. the quality of work of a smaller outfit may be better, due to reasons which I shall

investigate later; 4. the output of a small organisation is often comparatively larger than that of a large

one. Considering the activity of privately owned Swiss organisations one may conclude

that they are heavily influenced upon by the following factors: 1. Absence of fl ight problems; 2. Pat tern of organisation of the Swiss Cadastral Survey and its influence upon com-

petition and price policy; 3. Possibility of carrying out private jobs; 4. Existence of an excellent triangulation network from 1st to 4th order throughout the

country.

1. Absence of Flight Problems. It is a well-known fact that Switzerland has no private flying organisation special-

ising in photogrammetric flights. All aerial photography is done by Federal organisations such as the Federal Topographical Service and the Federal Directorate of Cadastral Sur- veys. The fl ights for cadastral surveys and for the Federal Topographical Service are carried out systematically according to a program worked out by these organisations.

I f a private photogrammetr is t needs aerial photographs for certain of his jobs he files a request for a special f l ight with the office in charge, indicating flying height or image scale and f l ight course. These f l ights are charged to the tar i f f presently in Vigour. I t is seldom that these requests are turned down. Actually the surveying authorities go to great pains to satisfy the demands of private offices.

I t must be mentioned that these Federal offices are extremely well equipped with

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aircraft , cameras and competent personnel. The photographic material, ei ther films or plates, which the private contractor is supplied with is generally above reproach.

Due to this fact, the Swiss photogrammetr is t cannot get acquainted with the various problems in connection with the organisation of photographic fl ights, at least as long as his field of activity is limited to Switzerland. Considered f rom the point of view of pro- fessional formation this is to be regretted. The advantages of this system are however by fa r prevailing, since the private contractor needs neither aircraft nor aerial camera. Fur thermore he is not running the risk always connected with flying. Of course it does not mean that the private contractor knows nothing about flying and taking photographs. In general he is quite well aware of the various problems.

2. Organisation Pat tern of the Cadastral Survey and its influence on the price policy.

The fact that 260 surveying offices and 8 photogrammetric organisat ions are doing business in Switzerland is due to the circumstance tha t the Federal Government does not carry out the Cadastral Surveys, but merely acts as coordinating cen t e r . Besides the photographic f l ights the government takes care of: a) the supervision and coordination of the various jobs and the set t ing up of rules; b) the technical supervision of the 4th order triangulation, of the basic topographic map,

of aerial phot0gramrpetric projects and their control; c) the examination of cadastral surveyors.

These tasks incumb to the Federal Department of Justice and Police, to whom the Federal Director of Surveys and his s ta f f are responsible.

The manner in which the Director of Surveys described the organisation of cadastral surveying is characteristic. He said:

"It is a definite advantage tha t our organisation which stems from the historic development and economic structure of our country leaves the mayor part of cadastral surveying and soil conservation to private surveyors. The Swiss is averse to large organi- sations of state officials and to the concentration of power resulting therefrom. Survey- ing and soil conservation would be a lot less popular if it were carried out by functionaries. We know from experience that private enterprise, independent work and the sense of responsibility are a stimulus for healthy initiative. They also counteract to the danger of stagnation in the surveying profession. Many an improvement of ei ther working method or instrument is due to the initiative of a private surveyor. In order to offset the dis- advantages of this system the following four measures are however necessary: 1. Precise instructions as to the technical execution of a job, set t ing up of model forms,

drawing regulations and error tolerances; 2. Careful checking of the work by state surveying offices; 3. In case of neglect of duty, punitive measures up to the withdrawal of licence must be

laid down in the regulations concerning the licensing of cadastral surveyors; 4. Regulation o f surveYing fees:.:~witzerland has surveying ta r i f f s which go much to the

detail and which are revised periodically by a joint committee of the Surveying author- ities and the Association of "Cadastral Surveyors."

Insofar as cadastral surveying is concerned, the Swiss photogrammetris t has to fear no price competition. To my way of seeing it, this is a positive feature saving both time and money which otherwise, under the rule of free competition, would have to be invested into publicity and efforts of hustling up business. Furthermore price dumpings as well as exaggerated fees or shoddy work are thus eliminated. The only facts which influence on a job being entrusted to a specific organisation are its working capacity, its ra t ing as to the quality of its work and its location. I t may be "that certain capacities which served as a base for the calculation of the tar i f f were set too high, the prices for certain kinds of work thus being too low. However these slight discrepancies can easily be straightened out by discussing this problem in a liberal and objective manner. This point of view is of course strictly personal. However I believe tha t many of my colleagues will bea]~ me

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out. As I can see it, the opinion tha t working conditions and prices are bet ter in other countries is erroneous.

Anyone who knows the photogrammetric world from experience must be aware that where free competition dominates a country's surveying activity, there rages a merciless war of competitors with all its well-known and undesirable attr ibutes such as graft , price dumping, shoddy work due to exaggerated working speed in order to compensate for understated prices. When tending an offer false s ta tements are made (e.g. impossible accuracy is promised) and generally the most fantast ic methods are vented.

It is regrettable that photogrammetris ts , ei ther by ignorance or for the sake of com- petition, talk and write about tolerances of accuracy and economy which are obviously wrong. These people are a danger to serious photogrammetry since they give the buyer the idea that photogrammetry can do anything and that any amount of money can be gained. Thus the prices are cut unduly. We can only hope that the proper authorities see through these publicised results. Otherwise the SWiss photogrammetr is t is to be regretted.

3. Possibility of carrying out private jobs.

A circumstance which influences favourably on the activity of private photogramme- tric organisations is the fact that the photogrammetric insti tutes of our universities carry out neither cadastral surveys nor private jobs. Their ins t ruments serve exclusively re- search and tuition purposes. This solution seems to me the only correct one, since it would be unjust tha t instruments which had been purchased with public funds compete with privately owned ones.

As private jobs may be designated the establishment of maps needed for the con- struction of hydroelectric power schemes, of roads, bridges etc., the completion of cadastral maps by contour lines for town planning and urbanism, the preparation of topographic data for irrigation or soil conservation schemes.

4. Existence of a triangulation network.

For the determination of control points, the Swiss photogrammetr is t has at his disposal an excellent network of triangulation points, ranging from 1st to 4th order (4450 1st to 3rd order points and 65000 4th order points). The determination of control points, if done by a terrestr ia l method, generally is achieved by complementing the 4th order net by means of a currently used method.

The photogrammetr is t will thus not have to s tar t f rom scratch when creating a triangulation network. He will also rarely encounter problems in connection with aerial tr iangulation on a large scale. These problems will arise only when he is doing business in foreign countries.

The influencing factors in the activity of Swiss photogrammetr is ts having now been shortly dealt with, I shall t ry to have a closer look at this activity.

Organisational and Pe~lso~tnel Q~esbions.

Even for a small outfit, the choice of the rooms, the internal ar rangement of the various departments and the placement of the plotting instruments can be a mat te r of some economic importance.

In the course of my activity both in Switzerland and abroad, I had the good fortune to visit quite a number of organisations. I t was most interesting to observe the differences of conception in the set-up of such an outfit. I often encountered offices where everything could be found in one single large room: plotting instruments, calculating machines, designers and all. Of this ar rangement I do not approve. For the operators a quiet and relaxed atmosphere is essential. The l ighting conditions also are quite different for a plotting room or a designing or calculating office.

Quite frequently also, too few attention has beerr paid to the erection of the plotting instruments. This is t rue especially for large; cities. 'The erection of an autograph on

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shaking wooden floors, often several storeys above s t reet level and in the neighbourhood of busy thoroughfares must be frowned upon, since the instruments will get out of adjustment easily. Loss of time, a considerable decrease of quality and efficiency and troubles of all sorts are ensuing. I t will always pay to see to it that plott ing is done in rooms which guarantee a pleasant working climate. This in turn will influence favourably on the condition of the instruments.

To the Swiss photogrammetr is t the personnel question is of paramount importance. Every care must be given to its solution. Efficiency, quality of work and therefore the economic success of an organisation depend to a large extent upon the professional standard of the personnel. The requirements as to accuracy set by our customers (Fede- ration, Cantons, townships or private contractors) are such as to demand that only f i rs t rate operators be employed.

It is well known today that good operators are scarce. Of necessity many orga- nisations will thus employ relatively unexperienced operators. Any manager and owner should however see to it that his personnel is up to its task, be it by delegating it to training centers for advanced studies or by training them within his own organisation.

Instruction courses are being held every year in various countries. There the photo- grammetris t- to-be will gain much theoretical and practical knowledge. However it is a fact that only in a well organised private organisation he can acquire the operating discipline necessary for smooth teamwork and the sense for the importance of his proficiency.

According to my experience the operators can be divided into four categories: 1. The full:fledged operators who, besides sharp eyesight and severe working discipline

have also the necessary theoretical and practical knowledge of surveying to be able to solve any problem independently. Any owner should do his utmost to have at least one such man per plotting unit.

2, Operators who are endowed with all these at tr ibutes but whose eyesight is limited to a certain standard of sharpness. These people must be used for certain categories of work only. They will not be able to carry out top accuracy plottings.

3. Operators who have good or excellent eyesight but are lacking in working discipline. The work they do is just sufficient and a fa int trace of carelessness makes itself felt in anything they do. Also they are lacking in reasoning power when interpret ing plotting details. Good nmnagement will help to develop these employees into reliable, proficient operators, since theirs is a problem of education ra ther than of technical training.

4. Operators who are convinced to have good eyesight and yet may carry out completely erroneous orientations or plottings, without even perceiving it. This is a deficiency which cannot be straightened out. I t is quite obvious that such operators are dangerous to any organisation. They must be shifted f rom the plotting section to another department. In our offices whose main activity consists of plotting large scale cadastral maps,

basic topographic maps and plans for civil engineering, the operators must be versed in topographic and cadastral work as well. Their task consists not only of routine plotting but comprises also the correct interpretation of the photographs and faultless drawing of details. In this connection the Swiss regulations as to the employment of personnel for cadastral surveys, dated 22nd February 1946, rule tha t plottings for cadastral surveys may only be carried out by licensed cadastral surveyors or by surveying technicians in possession of the professional certificate. The requirements for obtaining this certificate are the following: 4 years of apprenticeship with a licensed cadastral surveyor, 5 years of practice with same, 1 additional year of specialisation and finally an examination before a federal board of experts.

I t goes without saying that good operators without special diploma but endowed with good eyesight will also be employed. This will be the case in large organisations

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where they are carrying out plotting of all kinds not connected with cadastral sur- veys. Their work must however be checked constantly.

According to the organisation, i to 4 operators are needed for each plotting instru- ment. Personally I am strongly in favour of one chief operator for each group of 2 to 3 instruments. His task may be defined as follows: 1. He is responsible for the shifts being relieved without any disturbance. 2. The operators working under his supervision are to be carefully observed during

work. They must be tested in any respect in order to know their s t rong and weak points. They will then be assigned tasks according to their capabilities.

3. He must bear a hand when difficulties arise (e.g. difficult orientations, plotting of rough terrain, checking and adjusting the instrument) .

4. He is responsible for the maintenance of the plotting instruments. 5. Training of young operators will be his job. 6. He is responsible for the plottings to be prepared correctly and the plotting program

to be carried out on time. I t goes without saying that in order to be up to his task a chief operator must be

proficient himself. Furthermore he must possess organising talent and ethical qualities. An organisation lucky enough to have among its s taff such qualified personnel will not be lacking success.

The question of "specialisation at the plotting instrument" is not a privilege of large outfits. The manager or owner of an organisation with f rom 1 to 3 plotting instruments and 6 to 20 employees will also have to grapple with it.

This specialisation will depend upon the availability of personnel, the urgency of delivery, the climate, the economic situation and the human psychological factors. This applies above all to private organisations.

Government offices do not enter into account since: 1. Switzerland has no federal photogrammetric organisations, apart f rom the Federal

Topographical Service, which has to perform special duty. 2. Their economic reasoning is based on quite different suppositions, since their exis-

tence is not dependent upon the economic success, the status of public service being predominant.

Anyone who invests his money into plotting instruments is bound to use them as economically as possible and to get top performance. The question of how long it takes to pay off a plotting instrument is not an easy one, since it depends on many factors. If the organisation around the plotting instrument works intensively, capably and with qualified personnel the pay-off time may vary between 5 and 10 years according to cir- cumstances and price. If however a large s taf f comprising several directors and depart- ment heads is to be kept up, it will be wise to extend this pay-off time. And should the organisation work clumsily there is a good chance of its suffering heavy losses. At the condition that qualified personnel be available, high quality plotting instruments are a good investment:

A much-discussed question which is difficult to answer is the best way of organising the shifts. Thus H. Richter in ,,Leistungszahlen der t~hotogrammetrie '' holds that a set-up of two shifts of totally 14 working hours a day with an overlap of two hours, is eco- nomical, the working time lasting from 0700 to 2100 hours, which means 8 hours per shift and 7 hours each plotting time. This applies to German instruments operated by German personnel.

Mr. Le Divelec, Florence, in his publication , ,L'aerofotogrammetria per rilevamenti topografici a media scala su superficie estese" is in favour of 3 shifts of 7 hours each, totalling 21 hours of plotting time. He claims to have obtained best results thereby with Italian instruments and operators.

Prof. Kasper in ,,Die wirtschaftliche Leistungsf~higkeit der Pr~zisionsger~te ~fir die Luftbildmessung" recommends 18 working hours a day, e.g. three shifts of six hours

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each, overlapping each other. To him this a r r ange me n t seems the mos t economical one. Possibly Prof. Kasper thinks of Swiss plott ing Ins t rumen t s but not Swiss operators. Per- sonnally I have encountered in various organisat ions 24 hours of working t ime with four shif ts of six hours each.

As one can see there is no shor tage of possibilities. The choice as to which sys tem is to be preferred may however be somewhat of a problem. Dur ing my practice both in Switzerland and abroad I have tested all these various possibilities. Each one has i ts s t rong and weak points. In order not to add to the confusion I shall absta in f rom explain- ing the a r r angemen t which applies to my own outfit. It suffices to say tha t it is still another one, which I believe to be best suited to my needs. I do not know which sys tems are in favour with my Swiss colleagues. W h a t ma t t e r s most however is for each m a n a g e r to find the a r r a n g e m e n t most suitable for his proper organisat ion, according to the avail- able personnel and the specific l iving and working conditions.

There are some rules of universal value though: a) mult iple sh i f t s are economical only when there is enough proficient personnel avail-

able. It is bet ter to have less sh i f t s manned by capable operators than doubtful re- sul ts with unreliable ones.

b) Night sh i f t s are subs tan tua l ly less productive, approx, by 20 to 25%. Quality is also somewhat reduced.

c) When working out the rotation schedule for the shif ts one cannot proceed too sche- matically. The human side of the problem (compulsory i r regular life) cannot be overlooked. There also remains the question as to how ma ny hours of continuous work m a y be

expected of an operator wi thout running the r isk of physical and psychological distur- bances. I should say tha t six hours of continuous plot t ing are the utmost , a lways provided tha t he works continually and intensively.

Under normal conditions and with fully qualified operators i.e. 1 operator and 1 ass i s tan t working 8 hours the cost decreases by 20% for 12 plot t ing hours (2 operators, 1 ass is tan t ) and by 35% for 18 working hours (3 operators, 1 assistm~t). This mus t be considered as gross profit, which means tha t the decrease of efficiency o f the n igh t sh i f t has Mready been taken into consideration. We do not recommend to pay p remiums to operators, since pho tog rammet ry is no field f i t for the introduction of such competit ive measures . Compulsion in this field tends to deteriorate the quality. And the mone ta ry temptat ion may induce less reliable operators to neglect quali ty for the sake of quanti ty.

Having now dealt summar i ly with the organisat ion of a photogrammetr ic outfi t I shall explain short ly the kind of work which the Swiss pho togrammet r i s t is mos t likely to perform.

Plotting of basic maps (topographiv maps) in connection with cadastral surveying.

No doubt this kind of work is well known to anyone among you: Plot t ings most ly a t the scales of 1 : 2500, 1 : 5000 and 1 : 10000 with contour lines. As to the technical exe- cution there is hardly someth ing new to be said. I should however like to mention a few data concerning the accuracy attained. These da ta are taken f rom the official control reports. Hereaf te r an example of a job which was carried out in our offices: Val Muggio Project. Scale 1 :5000 , surface to be mapped 3625 ha (9000 acres) , mean slope of te r ra in 65%, image scale i 14000 approximately. a) Mean linear error of planimetr ic position, computed f rom 714 control measu remen t s

on 180 s ta t ions -+ 0.52 m = 35% of tolerance ( ± 1.5 m)

b) mean height error of spot heights , computed f rom 144 m e a s u r e m e n t s . -- 0.93 m = 94% of tolerance ( ± i metre)

e) mean he igh t error of contour lines, computed f rom 709 measu remen t s on 197 s ta t ions = 59% of tolerance (tolerance ~ -- (1 ÷ 3 tan a) m.

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More interesting comparisons can be made on the basis of the output. H. Richter in ,,Leistungszahlen der Photogrammetr ie" gives an output of approx.

9 ha (22 acres) per hour, inclusive orientation, at a scale of i :5000 and for mountainous terrain. Le Divelec in "Photogrammetr ia" gives a value of 10 ha (25 acres) per hour at a scale of 1 : 4000, and Prof. Kasper, also in "Photogrammetr ia" mentions an output of between 3 to 6 ha (7 to 15 acres). The latter values are perfectly in line with our own experiences. In 10 years of practical plotting our mean output per hour amounts to 5 ha (121/2 acres).

For the scale 1 : 10000 Richter gives a mean f igure of 25 ha (62 acres) while Kasper mentions a limit of from 6 to 15 ha. As to ourselves we are quite satisfied with approx. 10 ha per hour. Richter ulso gives a mean sett ing time of a s tereogram of 17.4 minutes for the relative orientation and 23.5 minutes for the absolute orientation, totalling 40 minutes. Another 39 minutes are mentioned for prepar ing the stereogram. Unfor tunately it is not quite clear what precisely is to be understood by "preparing".

Calculating the mean sett ing time from about 8000 stereopairs I get a mean value of approximately 2 hours. Frankly I must say that I never succeeded in at taining the results claimed for by H. Richter and Le Divelec. This may be due to the topographic conditions in Switzerland which are more complicated than elsewhere. However I should strongly advise against basing one's offers on these data. I f you wish to s tar t a photogrammetric bureau of your own, you had better settle for 2 hours - - which is normal - - than 40 minutes. Remember tha t in photogrammetric practice t h e r e may arise many difficulties which will play havoc with your optimistic calculations.

In this connection it is gra t i fy ing to learn that Prof. Finsterwalder needs 3.4 hours of setting time per stereopair of the Vogelberg terr i tory ownership map.

Aerial photogrammetric ownership maps for reallotm~n$s.

There is much talk in photogrammetric circles of aerial polygonation and aerial triangulation in extensive surveying - - and rightly so. The industry is designing new plotting instruments and aerial cameras for this kind of work - - and again rightly so. But under no circumstance should largo scale mapping, especially large scale cadastral surveying be neglected over this. The proper method for this work, which is of extra- ordinary economic importance for any nation, needs also suitable photogrammetric equip- ment. Any practical photogrammetr is t dealing with cadastral surveying knows however that not all instruments which may be perfectly well suited for extensive surveying, have the qualities necessary for cadastral surveying. In this connection I think of the use of film for taking photographs, of the cameras which lend themselves to vertical photographs only and of the comparatively large picture sizes, which aU of them are negative factors. I t is good to know that the persons at the head of our famed photogrammetric industry axe on to the problem and busily seeking for an answer. B y means of scientific trials and in close contact with both surveying authorities and practical users they strive to develop such equipment.

As to working methods, efficiency and prices for aerophotogrammetric ownership surveys there exist several detailed publications. I think I can dispense with repeating facts already known.

Today, af ter 10 years of activity in this special field we may safely call the ways and means now in vigour as perfectly up to date. Each of its branches (signalising boundary points, determination of control points, checking in the field, plotting, drawing and reproduction) has been thoroughly studied. Signalising of boundary points by means of cardboard panes 20/20 cm in size has proved perfectly satisfying. In order to give you an idea of the intensity of work prevailing in a Swiss photogrammetric office, I may be allowed to state tha t our organisation alone, in 10 years of activity, has surveyed and mapped among other jobs 50 municipalities in the Canton Tessin only, at the scale of 1 : 10000, the mapped surface totalling 10000 ha (24700 acres) with approximat.ely 180000

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lots. This work was carried out with 1, partially with 2 plotting instruments. The mean values for these jobs are:

slope of terrain : 36% number of lots per ha (21/~ acres) : 18 buildings per ha : 2 number of plotted photographs : 750 pairs orientation time per pair : 3 hours output : 2.8 ha per hour number of lots plotted : 55 per hour

On the basis of these results one can say tha t by using the photogrammetric method for regions without cadastral maps, the Canton of Tessin alone has saved from 250 000 to 300.000 Sfr. at the same time speeding up the agricultural reorganisation.

Cadastral Surveying by Aerial Photogr~zm/metry.

Two detailed publications by Hf i r ry - -Pas to re l l i~Sola r i give detailed information about this most recent field of use of aerial photogrammetry: e.g. , ,Photogrammetrische Grundbuchvermessung" 1952, and ,,Progr~s dans la mensuration cadastrale photogram- m~trique" 1953. I assume that these publications are known so tha t I can dispense with giving details. As Dr. H~irry points out in one of his articles, the use of photogrammetry in Swiss cadastral surveying for producing official cadastral maps at the scale of 1 : 1000 marks a new step in this field. A totally new field of activity is opened to the photo- grammetrist , which calls for th a still closer cooperation between photogrammetr is t and cadastral surveyor. I t is also open ground for most interest ing technical and economical experiments.

The introduction of the photogrammetric method for cadastral surveying requires highly skilled operators. When it comes to property rights and their legal status a har- monic cooperation between technique and law is undispensable. The absence of such knowledge is bound to cause heavy disappointments.

Other photogram~etric jabs.

Besides establishing the basic topographic map, surveying the property situation for reallotment schemes and eadastral surveys the Swiss photogrammetr is t also provides plans for civil engineering, town-planning, forestry, etc. The numerous hydro-electric projects have also favourably influenced upon photogrammetry.

From time to time terrestr ial photogrammetry is also used, especially in connection with hydro-electric projects, excavation studies, building reduced scale models for water supplies, chart ing gorges and rocky slopes.

Due to this many-sided activity the Swiss photogrammetr is t is given the opportunity to use all kinds of Swiss made plotting instruments and cameras. Thus .we know of the new "Aviotar" and "Aviogon" lenses, the new RC 5a and RC 7a cameras and A7 and A8 plotters.

Above all the Swiss photogrammetr is t is doing large scale plotting. I am of the opinion that this kind of work is best suited for testing aerial cameras and plot t ing instruments (besides aerial tr iangulation). The personnel also is being put to a severe trial and is thus induced to give of its best.

A relatively small outfit has the f u r t h e r advantage to allow the owner to personally supervise all departments and to see to it that every job which leaves his office is up to standard.