The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
1336 
A basic-point to define a traditional analogue photo campaign, 
is the camera frame or the image-extend, meaning the resulting 
area on the ground that is covered through one image by the 
analogue camera. 
All “full size” analogue aerial cameras use the same frame size, 
defined by the film size of 23cm by 23cm, and by that also 
represent the same image-extend on the ground - given a 
specific camera lens system (focal length) and a specific flying 
height. 
This is not the case for the digital cameras, where CCD’s has 
substituted the traditional film-media. There are big differences 
on how the cameras CCD’s are combined and arranged into the 
final image-frame. And by this, also different resulting image- 
extends. 
Because there is no exact conversion from one single analogue 
image-extend to the various digital CCD frame image-extends. 
The term image-extend is no longer used in the specification 
for a KMS digital photo campaign. 
3.2 Image-scale / Flying height 
For an analogue photo-campaign, it is also necessary to define 
the two interacting parameters image-scale and flying-height. 
Image-scale is the most commonly used and exact term, which 
through a predefined camera-lens-system (and image-extend), 
also specifies the exact flying height. 
For a digital image campaign, image-scale and flying-height are 
also interconnected and by so it is only needed to specify one of 
them. 
The image-scale specification for digital cameras, are the 
definition of “ground sampling distance” (GSD). The GSD 
defines what size on the ground that has to be represented in 
one pixel. Normally the GSD are specified as “X centimetres” 
meaning that one image pixel (must) represent “X centimetres 
by X centimetres” on the ground (flat ground). 
Specification of GSD is sufficient and preferable to substitute 
the traditionally definition of both image-scale and flying- 
height. Using the GSD, the specification is neutral to which 
digital camera could be used. Different cameras with different 
camera-lens parameters will adapt the requested GSD, by doing 
the data-collection from different flying heights. 
3.3 Coverage / Flight lines 
By the fact that the different digital cameras consist of different 
image extents, the cameras do also cover various areas on the 
ground, given a specific GSD. This is also the case when 
compared to an analogue camera. 
A transition from analogue to digital image campaigns, or “year 
by year” transitions between digital camera types, will therefore 
cause ongoing fluctuations in “ground coverage” on images and 
by that also fluctuations in “number of images and number of 
flight-lines” needed to cover a specified image-campaign. 
When the production, as for KMS, is highly repetitive and 
based on tenders with possible changing contractors, the image 
footprint and number of images for each campaign are very 
seldom constant over years. 
3.4 Summary 
At KMS, the first revision of the tender material to adapt a 
digital production, resulted in exclusion of all references of 
image extends, camera lens system, flying height and image 
scale. Instead the GSD “ground sampling distance” was 
introduced and substituted to describe matters where the 
excluded specifications were used. 
These matters do in some ways simplify the tender, by 
focussing on only GSD as the primary specification of a photo 
campaign. But other parts, as missing continuity in technology, 
image positioning and image extend (by different camera-types) 
could cause a more complicated tender evaluation and 
production QA. 
In table 1 is shown an overview of these discussed elements. 
Subject 
Analogue 
Digital 
Image extent 
Same for all 
camera-types 
Differs for each 
camera-type 
Flying height 
Exact for each 
image scale 
Differs for each 
camera-type 
Image scale / 
GSD 
Image scale... 
exact 
GSD.... exact 
Coverage 
Exact for each 
image scale 
Differs for each 
camera-type 
Table 1 : aspects on analoug/digital camera-types 
4. EVALUATION OF WORKFLOW AND 
END-PRODUCTS 
In the production workflow, the different phases of planning, 
tender, data collection, logistics, data processing, 
documentation etc. have all shown elements, where the use of 
the digital camera technology causes serious considerations and 
serious need for changes. 
These different workflow-phases of the digital image data 
collection will be discussed. Critical points and recommended 
practical solutions will be presented and argued. 
4.1 Planning 
The initial revision of the KMS photo campaign tender-material, 
was focused on the referred matters presented in section 3. To 
allow data capturing with digital cameras, all references of 
image-extend, camera-objective, flying-height and image-scale 
had to be removed from the tender material and substituted with 
the term “ground sampling distance” (GSD). 
To consider, is also the effective “ground coverage” of each 
image, which, in case of digital production, is depending on the 
camera type used by the chosen contractor. Therefore a pre 
flight planning of image positions and image frames, should no 
longer to be part of the tender material. 
The pre-planning was earlier produced and estimated by KMS. 
Results was given as information to the tenders, as input for 
there calculations and price-estimations. 
Planning now has to wait until the contractor and thereby the 
camera type has been defined. This means that each tender now 
have to do his own pre-planning, to estimate the necessary 
workload and a price.