, no other 
F the aerial 
area. By 
he camera 
r the GPS 
ennae. 
ographs of 
analytical 
nd control 
theoretical 
ve photo- 
should be 
xpected in 
nt referred 
metrically 
ents were 
he further 
ns of the 
e accuracy 
al of the 
the mean 
cm for the 
ric errors, 
to be kept 
IS. 
c and GPS 
ctive GPS 
ll concern 
coordinate 
narizes the 
en over all 
d stations 
1e detailed 
o different 
are clear 
direction, 
n not to be 
nsiderable 
ntial error 
e been re- 
airplane: L 
n, + to the 
ecially the 
ndicular to 
ctically no 
hose mean 
an be seen 
rically and 
nt shifts 
  
  
  
  
  
N Station A S D F H Yn 
Stip« dm] 0 22 106 130 386 
--— 1 X -20 21 -205 
Y 1 3 1.0 
Z 41 -37 -39.0 
-— 2 X 18 20 19 19.0 
Y 24 -16 2 -14.0 
7 39 -33 44 -387 
4-3 X 2 -3 0 4 15 
Y 9 12 34 37 230 
Z 45 38 52 oou 41.5 
-— 4X 19 19 22 18 195 
Y 15 17 22 2. 20 
Z 44 -42 82 15 458 
-—5 X 1 2 2 3 05 
Y 18 16 34 58 315 
z 47 -41 -62 18 420 
> 6 X 14 14 14 13 14 13.8 
Y 22 24 -25 6 21 112 
Z 45 41 -49 57 19 -422 
WET 27 26 22 2523 24.6 
Y 6 3 17 17 28 14.2 
Z 44 38 -56 58 19 -35.4 
) uk 12 12 -18 T T -142 
Y 8 9 4 1 21 18 
Z 42 35 -51 43 8 -326 
4 o0 x 19 20 21 21 20 202 
Y 5 3 2 11 26 94 
z 45 43 -58 46 20 -424 
)'o x 7 7 5 8 7 -68 
Y 18 22 2 11 2 -14.0 
Z 53 48 -67 55 26 -49.8 
dat x 14 13 12 17 20 15.2 
Y 2 34 9.2 
z 54 48 48 17 11 312 
E x 6.0 59 83 08 gp 75 
Y -45 -51 45 1166264 4.6 
Zz |-450 400 -545 525 417 -404 
  
  
  
  
Table 1: Coordinate differences between photogrammetrically 
and GPS-determined camera air stations (arithmetic 
means of strips, antenna 2, Gauss-Krüger, in [cm]) 
  
  
  
  
  
  
A S D F H >/n 
L 10.3 10.5 8.7 10.2 10.6 10.2 
C 15.3 14.5 17.2 13.7 47.7 15.5 
V -45 -40 -54.6 -52.9 13.7 -40.4 
(-48.1) 
  
  
  
  
  
  
  
Table 2: Overall mean differences in L, C, V at air stations for 
each GPS ground station (antenna 2, in [cm]) 
  
  
  
  
  
  
40 
CO MR T RE 
LS, IDE 
g of 
2 - 
= ett 
9 -20r b 
o emt 
= eet 
Q -40 FT accents 
-60 mor : 
0 100 200 300 400 
Distance [km] 
— vem mem 
  
Figure 6: Overall mean differences in L, C, V at air stations as 
function of distance to GPS ground station (antenna 2) 
5 
(magnitude in flight direction 10.2 cm, across flight direction 
15.5 em, vertical -40.4 em). The variations of the blocks against the 
constant shifts are remarkably small, remaining within a band of 
+0.4 em to -1.5 em in L direction, resp. of +2.2 cm to -1.8 cm in C 
direction. As far as the mean vertical differences are concerned the 
most likely interpretation assumes a constant shift of -48.1 cm for the 
GPS ground stations A - F (up to 130 km distance). The block 
variations against the constant shift then remain within a band of 
*8.1 em and -6.5 em, whilst the results of station H would then jump 
out by 37.4 cm. It is assumed, in this case, that the outlier at station 
H may be caused by ionospheric error effects, which can be expected 
in that order of magnitude over a distance of nearly 400 km. 
The overall results thus are highly consistent, showing no distance 
effect, except for the z errors from the long baseline to station H. The 
question remains, however, what are the causes for the constant 
error magnitudes. As the constant errors are clearly related to the 
flight directions it can be stated that they must be caused by effects 
related to the sensor system of the airplane. This is in first instance 
the camera system with possibly small additional influences from the 
GPS antenna- and time- offsets. Constant photogrammetric errors at 
the camera air stations of 10 - 20 cm (at h = 2000 m) are quite likely 
to happen. It should be realized that we are concerned here with 
absolute errors which normally in photogrammetry are not visible (at 
the air stations) or are compensated by degrees of freedom. Whether, 
however, constant vertical errors of more than 40 cm can be 
attributed to the photogrammetric part remains doubtful, although 
there is no easy other explanation at hand. 
The assessment of the mean coordinate differences per strip (taken 
over all stations) between GPS positions and photogrammetric check 
values (like in Table 1) is here not carried any further. The variations 
against the constant shifts are now considerably smaller than in 
Table 1. They amount to magnitudes between +10 cm and -12 cm 
in L, resp. between +16 cm and -16 cm in C and still show some 
alternating effects, the causes of which must be in the GPS system. 
It could be effects of satellite constellations or related to the airborne 
GPS antenna. The z results are the same as of Table 1. They are 
particularly consistent, the mean differences per strip varying within 
*9 em and -9 cm. The analyses will be continued as soon as the 
other test flights will have been processed. 
4. PRELIMINARY CONCLUSIONS 
The results obtained so far can be summarized in a few statements: 
* The software succeeded to provide OTF ambiguity solutions in 
all cases, from all ground stations. 
* The restored trajectories still have some gaps, and they show 
some large systematic errors in parts of poor satellite 
constellations, especially in flight turns. Nevertheless, the 
trajectory parts of the photo-strips have been properly restored 
based on the antenna 2 recordings. 
* A warning has to be stated, that successful OTF ambiguity 
solutions still have to be checked on sufficient satellite geometry, 
before accepting the restored trajectory. 
* The direct comparison of photogrammetric camera air stations 
and their GPS positions showed considerable constant and other 
systematic errors which are related to the flight directions. The 
further analysis confirmed that a large part of the systematic 
errors relates to the aircraft sensor system. It means that with 
regard to absolute GPS positioning systematic discrepancies 
originating in the camera system have to be expected. Not really 
explained is a constant error in z of about 40 cm magnitude. 
* The check results show no dependency on the distance to the 
GPS ground receiver stations. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B6. Vienna 1996