Transcript The use of SRTM DEM data to delineate the SOTER Terrain Unit system for the European states Endre Dobos & Joël Daroussin.

The use of SRTM DEM data to
delineate the SOTER Terrain Unit
system for the
European states
Endre Dobos & Joël Daroussin
SOTER (SOil and TERrain
Digital Database)
 To
replace the only existing global soil
database at the scale of 1:1 Million
 Based on existing soil databases
Methodology developed between 1988 and 1995
Status of SOTER in 2004
Examples of uses:
assessing
land
degradation
processes
PROBLEMS….
 Inconsistency
of the data
 Interpretation of the map
content
 Outdated variables
 Edgematching
 Lack of data
 Unknown accuracy of the
source data
SOTER Procedure
Modification workshop
 20-21October,
2004, Ispra, Italy
 Agreement on the need to update and
revise the procedure published in 1995
 Create a guide line (a cooking book) to
harmonize the use of DEM to delinate
physiogarphic units, which maintain the
original meaning and idea of the
SOTER methodology.
 Test the procedure on Europe and
derive a SOTER database for Europe
Material
 SRTM
Digital Elevation model -
90 m
Pilot area
Carpathian-basin
Pilot area
Carpathian-basin
SOTER
 Mapping
Units are defined by
physiography and lithology
Physisography is characterized by 4 differentiating features:
1. Slope intensity
2. Relief intensity
3. Hypsometry (altitude in consideration of the relief intensity)
4. Dissection (PDD: potential drainage density)
Objectives
To build a quantitative, DEM based procedure
for the delineation of SOTER physiographic
units at the 1:1 and 1:5 million scales, following
and translating the original criteria defined in
the SOTER Manual of Procedure.
SRTM DEM (90 m resolution)
Continuous slope layer
Continuous RI layer
Continuous hypsometry layer
Continuous PDD layer
Block majority Reclassified
(block size: layers
990 m,(90
grid
m)resolution 90 m)
BlockResampling
majority (block
to the size:
block990
sizem,(resolution
grid resolution
990 m)90 m)
Resampling
to with
the block
(resolution
990 m)
Fitering (focal
majority
4 andsize
6 cells
radius circles
) (990 m)
Fitering (focal majority with 4 and 6 cells radius circles) (990 m)
The
SRTM DEM
based procedure
for deriviring
physiographic units
Combination of the four layers (990 m)
Fitering (focal majority with 3 cells radius circles)
Raster based generalization
• Elimination of the polygons under the size threshold
using the minimum Euclidean distance procedure
• Line simplification
Vector based generalization
Final physiographic units polygon system
Regional slope classification
Original
SOTER
0-2 %
Quantitative
procedure
0-2 %
Gently undulating
2-5 %
2-5 %
Undulating
5-8 %
5-8 %
Rolling
8-15 %
8-15 %
Moderately steep
15-30 %
15-30 %
Steep
30-60 %
30-60 %
Flat
Slopes
Resampled slopes
Classified slopes
Filtered slopes
Relief Intensity
…median difference between the highest and lowest point within the
terrain per specified distance. Units are m/km, m/slope unit, m/2 km
Changes of the approach: interpret relief intensity on an aerial basis.
0-50 m/area of a 1 km diameter circle
50-100 m/area of a 1 km diameter circle
100-300 m/area of a 1 km diameter circle
300- m/area of a 1 km diameter circle
Continuous relief intensity
Classified relief intensity
Classified and resampled
relief intensity map
Hypsometry
Level and sloping lands
with RI<50m/slope unit
Sloping lands with
RI>50 m/slope unit
Steep and sloping lands
with RI>600m/2 km
< 300 m
300 - 600 m
600 -1500 m
< 200 m
200 - 400 m
400 < …m
600 -1500 m
1500 - 3000 m
3000 - 5000 m
1500 - 3000 m
3000 < ….m
Hypsometry class
Elevation range (meters above sea level)
1
Up to 10
2
> 10 - 50
3
> 50 - 100
4
> 100 - 200
5
> 200 - 300
6
> 300 - 600
7
> 600 - 1500
8
> 1500 - 3000
9
> 3000 - 5000
10
Above 5000
Hypsometry
classes
Dissection

0-10, 10-25, and over 25 km/km2

Potential drainage density (PDD)
– 0-7 and 8-49
– I. Deriving surface drainage system based on digital elevation data.




1. flowdirection,
2. flowaccumulation,
3. recoding
cells having flowaccumulation value higher than a certain - resolution
dependent - value are assigned a value of “1” (stream cells) while all
others are assigned value “0” (background).
– II. A specified sized moving window is sent through the image for
counting the stream cells within a given area around each cell and the
output value of this function is assigned to the corresponding cell.
Potential drainage network
Potential drainage network density (PDD)
Potential drainage network
and
classified PDD
The PDD class ranges
Class
1: less dissected areas, convex
surfaces
2: more dissected areas or
depressions, concave surfaces
PDD value range
0-90
Above 90
The
resulting
PDD
layer
Combining
the 4 layers
Slope
Hypsometry
Relief intensity
to produce…
PDD
… the
raw
SOTER
physiographic
units
Vector based generalization
procedure
Select
polygons under the minimum size limit
Apply the minimum Euclidean distance method:
– Calculate the 4 mean terrain variables for each
polygon
– Calculate the Euclidean distance for each polygon
pairs
– Merge each selected small polygon into its
neighbour having the smallest Euclidean distance
Eliminating small polygons
Simplifying lines
 0.2
mm separability distance between
features on the printout
 Displacement of the vertices
with
maximum 200 and 1000 m ground units
respectively for the 1:1 and 1:5 million
scales
The
resulting
1:5 million
SOTER
physiographic
units
The
resulting
SOTER
physiographic
units
at
1:1 million
scale
The
resulting
SOTER
physiographic
units
at
1:5 million
scale
Comparing
levels of
generalization
raw
1/1M
1/5M
Conclusions
 There
is a strong need for standardized,
quantitative data based methodologies to derive
soil-landscape information at specified levels of
resolution.
 The 90 m resolution SRTM DEM is a promising
data source for 1/1 down to 1/5 million scale
soilscape delineation.
 The procedure can be translated to a purely
quantitative manner, maintaining all the
advantages of the quantitaive approaches.
 However, some criteria had to be modified to
meet the needs of a DEM-derived approach, like
Relief and PDD
Thank You for Your attention!