* PHOTOGRAMMETRY
—— 2D PHOTOCLINOMETRY
%
2%
GG
5
A
A
2
Mele.
2
2
2
2%
5%
5
V5
5
5
5%
2
7
“i
EZ
SS
SL
4
es
2
y
5
2
5
5%
1;
y
height [m]
ol
a
L 1
RA
RD SN
RN RR
ES
AE DRE SE RR EN
NEN SS
RSS SES SRI EUR N SS
N RRR EN
NS RR ER RRR RRR
RR RRR RRR RR RR RR RRR RRR
RRR RRR ESSEN RSS
NSS RSS SNO
NS RR RR OR RAR
Rn NENNEN S
SN RES x
N N S
NS SN PS
s SNS HHH; NN
SD ÉD Ne
N ES SSH
NSS SS SN
NSS RR S >
NSS a ES SAS
SN SN RRR
EEE LR SNS
SS SN SANARE
SED NE, ARS
= SD NE SN
Ss RRR IS
SN. NED. N N
SS NN ES
Ss SD ESS
SS Ss WRN RRR
NR RES?
SO
SSII
52
ZA
2,
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A
55
RD
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2
7
2
7
7,
f
%
%
4
2
ND
NSS
NORRIS
RRR
ORRIN
RRR
NSS
S
2
5%
7
2
2
%
ZZ
27
2
i
A
%
2
2
2
2
2
5
52
5%
2%
DR
AL
2%
5)
2
2
A
7
2
2%)
5
7
5
Ki
:
:
7
2
7%
7%
2
7
%
7
%
2
%
A
1
S
S
>
55
57%
A
(2
492;
2
7
Z%
7%,
7
7,
%
5
4,
2
Z
A
2
%
2
i
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%
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7
A
2
2
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7
%
GA
X
ZZ
27
=
Z 2%
05%
2,
ZZ
ZZ
,
A
ZZ
hy
] M. + PHOTOGRAMMETRY
14x1000 — A. —— 2p PHOTOCLINOMETRY
T T T T T T T T T T T T I T T 1
height [m]
* PHOTOGRAMMETRY
—— 2D PHOTOCL INOMETRY
SRR SS
ES RR
RRR RRR SS SS
NS SS RD 13.5 +
RR RRR RRR 3
RRR TH HR TTR =
RS S S ARS RN
SS SIN AS =
RN RRR RR DORN
ES RR RR RRR RN
TEN N
SRN S RRR NS À
ZEN NN NS =
RES a "
RE RRR a 3.0 +
S SS RSS RR RRR RR *
NN RR RRR AR RN x
X RA RRS S 3l
N RSS S RR E ^,
NS
Se rose Tr TT T T Tr
RRR RRR RRR
NHI
DANS 100 150 200 250
RRR i
RT rr RE sample [pixels
ES
PR NR RR
RSS QR NS DE N
AE. SS
NEN N NS »
NS ENT
RSR NOR N SS SESS . : : . :
RSA RSS S SE N >
PTS SES SS on el rojlles along Image lines
SONS: RSEN SR RE GE SS RN . . .
Pet SPP. RRR SSSNN
RD A SSP
Fe SISSE, ZN
NS SESS NS SS
MER RRR SN NS
EZ S S ESS ER
SS TTS NN NE
N es. =
ee S SS S
NS SON J
TR
s j craters are smoothe 18.2D, . oreover, the use o patc es
SS
ZN
NS
SD
tends to introduce small scale roughness in form of spurious Fig.4a.
„blocky“ structures with steep slopes at the patch edges. So, photogi
what we can trust in only is the large scale topography, the
p» small scale features are not reliable.
The photoclinometry models suffer mostly from two facts:
Fig.3a. Region II :terrain models derived from First, it is assumed that albedo is constant across the considered sun dire
photogrammetry (top) and 2D photoclinometry (bottom). part of image. This is because all contrast in the image data is the sha
interpreted in terms of topographic slopes to build the terrain
model (note that for photogrammetry albedo features are
appreciated because of enhancing the image texture). But for
impact dominated surfaces it cannot be ruled out completely
5. DISCUSSION that albedo features are present due to spreading of fresh
material over the surface. To cope with varying albedo,
An admitted weakness of our approach is that we have no photoclinometry prefers images at oblique illumination, such
access to absolute truth“ concerning the configuration of Ida's that topography is the overwhelming source of contrast. Under
surface. Hence, we have to restrict the discussion to the the considered conditions this seems to be fulfilled.
limitations of both models that give a priori arguments for the Nevertheless, albedo features remain a serious source of error.
realiability of the data. To search for albedo features or to verify other model
The most serious limitation in the photogrammetry models assumptions and parameters of the photoclinometry, we
here is connected with the use of patches at the image computed a number of shaded reliefs at different illumination.
correlation, as discussed in chapt. 3.1. This has in consequence Inconsistencies will lead to artifacts in the derived topography,
that surface features with wave lenghts smaller than about 14 characteristically in the form of ,stripes" in the up-and-down
pixels are not resolved adequately. Especially, craters equal or
smaller than this size are not resolved, and sharp rims of larger
Second.
effects
converg
in acco
reachec
decreas
does no
is reac
allthou;
used as
large sc
not reas
why t
photog
explain
248
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996
