22
(containing data from 2007–2009) were re-used on each occasion. However, all
field data were checked on aerial photos to account for major events that would
render them invalid for further use (e.g., sod cutting, tree removal and wildfires).
Therefore, the effective sample size for training and validation gradually decreased
from 2010 to 2012.
An overview of accuracies obtained after transfer can be found in Table 2. Not
surprisingly, accuracy levels decreased from level 1 (6 classes) to level 4 (24 classes)
because of the increasing level of complexity and fewer training samples per class.
It was also apparent that accuracy levels dropped from 2007 to 2012. This can be
explained by the increasing time gap between the acquisitions of the training data
(2007–2009) and the imagery.
Figure 4 shows the dynamics of an excerpt of the Kalmthoutse Heide as revealed
by the time series of image classifications. The sudden and large increase of Sfm
(bare sand with some mosses) in June 2011 was a result of a wildfire in May 2011.
In the following months and years, this bare sand was gradually recolonized, mainly
by Molinia caerulea (Hgm).
Table 1 (continued)
Level 1
Level 2
Level 3
Level 4
F Forest
Fc
Coniferous
forest
Fcp
Pine forest
Fcpc
Corsican pine
Fcps
Scots pine
Fd
Deciduous
forest
Fdb
Birch forest
FdbBirch forest
Fdq
Oak forest
Fdqz
Pedunculate oak
S Sand
dune
Sb
Bare sand
SbBare sand
Sb-Bare sand
Sf
Fixed sand dune Sfg
Sand dune with
grasses as
important fixators
Sfgm
Sand dune fixed by
grasses and mosses
Sfm Sand dune with
mosses as
dominating
fixators
Sfmc
Fixed sand dune
with predominantly
Campylopus
introflexus
Sfmp
Fixed sand dune
with predominantly
Polytrichum
piliferum
W Water
body
Wo Oligotrophic
water body
Wov Shallow,
vegetated
oligotrophic
water body
WovShallow, vegetated
oligotrophic water
body
Wou Unvegetated
oligotrophic
water body
WouUnvegetated
oligotrophic
water body
A Arable
fields
Ac Arable field
with crop
Acm Arable
field – Maize
AcmArable
field – Maize
Aco Arable field –
other crops
AcoArable field – other
crops
J. Vanden Borre et al.
(containing data from 2007–2009) were re-used on each occasion. However, all
field data were checked on aerial photos to account for major events that would
render them invalid for further use (e.g., sod cutting, tree removal and wildfires).
Therefore, the effective sample size for training and validation gradually decreased
from 2010 to 2012.
An overview of accuracies obtained after transfer can be found in Table 2. Not
surprisingly, accuracy levels decreased from level 1 (6 classes) to level 4 (24 classes)
because of the increasing level of complexity and fewer training samples per class.
It was also apparent that accuracy levels dropped from 2007 to 2012. This can be
explained by the increasing time gap between the acquisitions of the training data
(2007–2009) and the imagery.
Figure 4 shows the dynamics of an excerpt of the Kalmthoutse Heide as revealed
by the time series of image classifications. The sudden and large increase of Sfm
(bare sand with some mosses) in June 2011 was a result of a wildfire in May 2011.
In the following months and years, this bare sand was gradually recolonized, mainly
by Molinia caerulea (Hgm).
Table 1 (continued)
Level 1
Level 2
Level 3
Level 4
F Forest
Fc
Coniferous
forest
Fcp
Pine forest
Fcpc
Corsican pine
Fcps
Scots pine
Fd
Deciduous
forest
Fdb
Birch forest
FdbBirch forest
Fdq
Oak forest
Fdqz
Pedunculate oak
S Sand
dune
Sb
Bare sand
SbBare sand
Sb-Bare sand
Sf
Fixed sand dune Sfg
Sand dune with
grasses as
important fixators
Sfgm
Sand dune fixed by
grasses and mosses
Sfm Sand dune with
mosses as
dominating
fixators
Sfmc
Fixed sand dune
with predominantly
Campylopus
introflexus
Sfmp
Fixed sand dune
with predominantly
Polytrichum
piliferum
W Water
body
Wo Oligotrophic
water body
Wov Shallow,
vegetated
oligotrophic
water body
WovShallow, vegetated
oligotrophic water
body
Wou Unvegetated
oligotrophic
water body
WouUnvegetated
oligotrophic
water body
A Arable
fields
Ac Arable field
with crop
Acm Arable
field – Maize
AcmArable
field – Maize
Aco Arable field –
other crops
AcoArable field – other
crops
J. Vanden Borre et al.