71 
>, Vol. XXXVIII, Part 7B 
In: Wagner W., Székely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
July . October 
:r field 
''V polarisation 
nad-leaved crops and 
l area 
range in October after 
conditions. On winter 
/ered in March when 
IBCH-codes 17-19). 
>-8 dB and remain on 
uly before harvesting 
it crops show that 
>m those with narrow 
erence in backscatter 
ferentiate within the 
broad-leaved crops due to the time difference in development of 
ground covering leaves. For asparagus there is a widespread 
backscatter distribution recognizable for all acquisition months. 
The maximum backscatter values (up to -2 dB) are reached in 
March, July and October. Lowest values (below -14 dB) were 
noticed in April and June. The structure of the asparagus plant 
and the plantation in rows seems to influence the reflection 
strongly. 
The analysis of the VV polarised signal shows a very similar 
backscatter for broad-leaved crops when compared to the HH 
polarised signal. Just a minor decline of values occurs at all 
dates. 
0 
-2 
-4 
-6 
Ì -8 
V 10 
-12 
-14 
-16 
-18 
-20 
0 
-2 
-4 
-6 
B” - 8 
J -10 
-12 
-14 
-16 
-18 
-20 
0 
-2 
-4 
-6 
i -8 
V 10 
-12 
-14 
-16 
-18 
-20 
March . April . June , July , October 
9 4 
' I 
I I 
.oat 
rye 
$ 
i ,i 
!i! I 
ii 
wheat 
Mean backscatter per field 
• HH polarisation 4 VV polarisation 
Figure 2: Backscatter distribution for grains in Fuhrberg area 
Grains: Backscatter values for grains (Fig 2) differ decisively 
from broad-leaved crops. In April, the values exhibit a decline 
to <-10 dB despite of the different phenological stages for 
spring and winter grains. In April 2009, spring grain started the 
development of first leaves (BBCH-codes 11-14), while winter 
grain finished the development of tillers and started elongation 
(BBCH-codes 29-31). But, these strong differences in the 
canopy structure and ground cover between winter and summer 
grains are not mirrored in the backscatter. After development of 
closed canopy in June, backscatter values remain on low level 
(<-11 dB) except from most oat fields where values remained 
above -12 dB. The backscatter of some barley and rye fields 
declined to -15 dB, while wheat and oat never cross the line of 
-14 dB. During June acquisition, all grains began flowering or 
fruit development (BBCH-codes 61-75). The values for barley 
and rye in July rose to >-12 dB. Most barley fields have a mean 
backscatter distribution of -9.5 to -12 dB. Rye fields have a 
mean backscatter from -8 dB to -12 dB. The backscatter values 
for wheat and oat remain on the level of June. Nearly all grains 
finished flowering and fruit development and were at stage of 
ripening (BBCH-codes 83-89) in July. Distribution of mean 
backscatter during October acquisition differs on wide range 
due to different dates of harvest. 
Except for oat, backscatter of VV polarised measurement show 
a strong decline of approx. -2 dB in June and July compared to 
HH polarised data. For other months and for oat this effect 
cannot be recognized or the decline is not as strong. 
Within the group of grains, oat is clearly discriminable because 
the backscatter values in June do not decrease. 
Grasslands and meadows: For grasslands and meadows there 
is a characteristic low backscattering of the radar signal in 
March (Fig. 3). Its distribution ranges from -10.6 to -14.3 dB. 
The values are lower than for most other crops at this time. 
Thus, grassland could be easily discriminated from grains, bare 
soil in preparation and intertillage crops which existed on other 
fields during March acquisition. Backscattering during 
acquisitions in April, June and July is similar to the one of 
grains. In April and June, the mean backscatter is <-12 dB. It is 
equally distributed up to -16 dB. In July, backscatter values 
reach >-12 dB; the phenology varied because of previous 
swathe. October values then reach the level of March again. 
In VV polarised mode measured backscatter signal is lower than 
HH polarised signal for all acquisition month. This effect is 
strongest in July: VV values differ from HH values by approx. 
2 dB. Due to the low backscatter values in March differentiation 
of grasslands/ meadows and grains is possible. 
Mean backscatter per field 
• HH polarisation * VV polarisation 
Figure 3: Backscatter distribution for grassland and meadows in 
the Fuhrberg area 
3.2.2 Gorajec area: 
Broad-leaved crops: Sugar beets show backscatter values 
between -8 and -lOdB in June. From July to September sugar 
beet fields remain on a high value (>-8 dB). Compared to sugar 
beets in Fuhrberg area, backscatter rises during summer month