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Proceedings, XXth congress

International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004

Some errors in rolls, runs, photos and counters number are
detected. The approximated photo centre coordinates (APCC)
was made by hand. At time of photography, no aerial camera
was equipped with GPS or INS. In the fact, this APCC could
be wrong for some miles (fig. 1).

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Fig.1. Overview of the project location
a square is map sheet 1:50.000 (15' x 15)
From the pre-selected photos, a paper copy will be made. The
paper copy will be then layout to get the optimal combination
between photogrammetry quality and minimum cost. The
Potential GCP placement will be done simultaneously on the
layout, and thereafter the layout will be snapshot to have good
1.3 The Selection of Potential GCP
A big problem for this project is the fact that: (1) there a large
number of aerial photos; (2) the photos are heterogeneous; (3)
the photos are older than 5 years; (4) there is no premarked
ground control on photos; (5) there is no kinematics-GPS on
board of photo-position for aerial triangulation. In addition,
the post GCP-survey would be very hard. The problem is
focused also to identify the place on photographs to the current
situation and to get the place.
The problem to make post-GCP for successive aerial
triangulation is to identify the suitable points. These natural
GCP should fulfil at least 4 requirement: (1) the point must be
good geometrically distributed, (2) the point must be clear
identifiable on photographs, (3) the point could be found again
now — although gap of more than 10 years, (4) the point must
be accessible — partially using helicopter. Points (1) and (2)
will be decided by photogrammetrist on the office. Point (3)
will be decided by photogrammetry-surveyor on field. In case
of survey by helicopter, point (4) will be decided by pilots.
For one full sheet (ca. 160 photos) at least nine GCP must be
found and some others must be selected as reserves. In the
reality, this job is often very difficult due to the low quality of
the photos or the fact of the objects (just jungle without
texture, or texture but without access possibility (fig.3).


Fig. 2. Lay outing of Photo and Planning GCP location
1.4 GCP Survey using Helicopter
For GCP survey using helicopter, a good plan must be
established. Due to the difficult area, some logistic base
camps and fuel points must be selected. Base camp is
normally place where there is minimal a house which could be
used for several day for crew. Important is water. Food should
be brought by our self. Electricity must be also generated by
own generator. Fuel to the fuel point must be transported by
boats or land vehicle. This fuel point must be place where
helicopter can land, although it is not a helipad.
During the survey, all necessary equipment must be taken to
the field, including some laptop computers, also CD writer for
backup, printer, GPS navigator, digital camera, etc. For
communication, satellite hand phone will be used.
Unfortunately, the data channel is not yet established, so data
store to the office could not be done. Consequently, a special
procedure is applied to guarantee that in all data is saved.
Data is copied to two laptops, USB-Hard disk, and some CD.
Regularly, the CD is sent by snail-mail to the office if post
office is found. The whole campaign is about 60 days, and we
don't know what happened during these days. To avoid data
loss if accident is occurred, during moving, laptops, USB-HD
and CD bearer should not be in same helicopter. The
campaign will be carried out by three helicopters.
Helicopter operation is rather expensive, but in almost points
in the jungle of Kalimantan, it is the only way to get the points.
The more serious problem is to identify the point, since the
photographs is made about 10 years ago. In Kalimantan
jungle, the most accurate point for ground controls is manmade
objects like bridge or county-office house. Once it is created, a
renovation is rather seldom. The second accurate point is
Mouth River to another river. However, sedimentation or
crosion could change this landscape. The third and last
alternative is logging road or logging airstrips. Some of them
are changed, leaved already or many new are created, so
identifying is very difficult.