7 
6. Time : There are several 
ficant and demand due attention (eg. ,obsolescence, depreciation, discoun- 
ted cost, obtainability cost, etc.). While obsolescence and depreciation 
are generally understood by us, discounted cost and obtainability cost 
are overlooked. Assuming that the money to purchase an instrument is bo- 
rrowed at an interest rate (i), compounded annually for the number of 
years (n), the total cost (C) in this case is related to the purchase 
price (p) according to this formula (routinely used by many bankers): 
cost functions of time which may be signi- 
  
  
C =- np A — 
[Hi - (+1) 1/1 
  
  
  
eg., consider, p = $10,000.-; n = 10 and i = 8%; then C = $14,900.- 
It is recognized that a present monetary unit is worth less than the cor- 
responding future monetary unit. If the economic conditions are in agree- 
ment with this concept then the procurement of that unit at the present 
time will cost less than in the future and a discounted cost is in order 
(see Hitch & McKean [3]). Against this, the concept of obtainability 
cost implies that alternatives which have a later obtainability date 
should have their costs raised correspondingly for comparison with other 
alternatives is a distinct possibility. 
7. Performance : Some output parameters have significant effects on 
the system cost. This can be assessed by means of sensitivity analyses 
after identifying the critical parameters (eg.,numerical data, chart, 
etc., identifying the phases of operations). The net result would be an 
expression of the functional relationship between a system's parameters 
and cost, popularly known as "Cost Estimating Relationship" (CER). 
8. Geographical Location : Costs are largely location dependent, more 
so when the product is to be deployed in a distant land and/or based on 
equipment, labor or material obtainable from a distant land as is common 
in the non-topographic applications of photogrammetry. 
  
Cost-model 
After reconing the cost factors, the appropriate elements of cost can 
dimensional), showing physical cost 
functions against phases of operation. In case of a non-topographic app- 
lication, the phases of operation like Control, Data acquisition, Data 
will have to be shown in the matrix (Fig 5,after Seiler[6]. 
be arranged into a matrix format (2 
analysis, etc. 
Finally, in arriving at a total system cost, it would be more meaning- 
ful, due to prevailing fluctuations in the economic conditions, not to 
present cost as a single figure (eg. ,$10,000.-) but an estimation with an 
index of uncertainty (eg.,$10,000 t $200). The above indicates that the 
cost-model is a series of summations. Let us now consider the Effective- 
ness-Model and the involved factors. 
Effectiveness factors 
One would evaluate the expected (a priory) 
1. Performance (accuracy): 
tribution of possible performance values 
performance (P) based on a dis 
that would fall within given statistical limits. 
2. Availability (A): The expected availability is the next factor con- 
ld "derate" the basic performance parameter 
ailable during allocated 
sidered in the sense it wou 
(eg., systems requiring maintenance may be unav