Logging methodology decision-making with the new high-resolution DEM of Türkiye

Abstract

There are many ways one can decide if an engineering related undertaking would be feasible and productive when the topography is thoroughly and precisely investigated before it takes shape. Forestry is just one profession that proper planning is of the essence when it comes to the logging phase of the entire production process. Logging in Türkiye is primarily handled over an ever-growing forest-road network. Although the specialized equipment e.g. yarders, tractor-winches, are also put into the works, their share and production capacity is limited and confined to certain parts of the country. Thus, timber production primarily revolves around direct tractor-skidding throughout the forest floor, taking the felled log from the stump to the nearest road. Here, topography is the real constraint in production method decision-making. Topographic maps have long been used to extract topographic parameters. However, Türkiye recently announced the completion of first national high-resolution digital elevation model, 5 m DEM. High precision, which would be achieved utilizing this DEM, reemphasized the importance of slope and topographic roughness in primary transport planning. In this study, we calculated the amount of slope and topographic roughness acreages in two forest planning units based on elevation differences. Both yielded enough extreme surface acreages, which would question the expansion of road building and justify the adoption of specialized equipment.

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7th Intercontinental Geoinformation Days (IGD) – 18-19 November 2023 – Peshawar, Pakistan
* Corresponding Author
Cite this study
*(aoaltunel@kastamonu.edu.tr) ORCID ID 0000-0003-2597-5587,
(oesakici@kastamonu.edu.tr) ORCID ID 0000-0003-4961-2991
Altunel, A. O. & Sakici, O. E. (2023). Logging methodology decision-making with the new
high-resolution DEM of Türkiye. Intercontinental Geoinformation Days (IGD), 7, 176-179,
Peshawar, Pakistan
7th Intercontinental Geoinformation Days
igd.mersin.edu.tr
Logging methodology decision-making with the new high-resolution DEM of Türkiye
Arif Oguz Altunel*1 , Oytun Emre Sakici1
1Kastamonu University, Faculty of Forestry, Department of Forest Engineering, Kastamonu, Türkiye
Keywords
Abstract
DEM
Slope
Topographic roughness
Acreage
There are many ways one can decide if an engineering related undertaking would be feasible
and productive when the topography is thoroughly and precisely investigated before it takes
shape. Forestry is just one profession that proper planning is of the essence when it comes to
the logging phase of the entire production process. Logging in Türkiye is primarily handled
over an ever-growing forest-road network. Although the specialized equipment e.g. yarders,
tractor-winches, are also put into the works, their share and production capacity is limited and
confined to certain parts of the country. Thus, timber production primarily revolves around
direct tractor-skidding throughout the forest floor, taking the felled log from the stump to the
nearest road. Here, topography is the real constraint in production method decision-making.
Topographic maps have long been used to extract topographic parameters. However, Türkiye
recently announced the completion of first national high-resolution digital elevation model, 5
m DEM. High precision, which would be achieved utilizing this DEM, reemphasized the
importance of slope and topographic roughness in primary transport planning. In this study,
we calculated the amount of slope and topographic roughness acreages in two forest planning
units based on elevation differences. Both yielded enough extreme surface acreages, which
would question the expansion of road building and justify the adoption of specialized
equipment.
1. Introduction
Digital elevation models (DEM) since the global
dissemination of SRTM data in 2005 have come a long
way. It was plagued with voids at the beginning, and
studies showed how they could effectively be patched
(Grohmann et al. 2006; Ling et al. 2007; Gallant and Read,
2009). Announcement of the first version of Aster GDEM
in 2009 provided additional support for further
strengthening SRTM’s later versions (Reuter et al. 2007;
Altunel, 2018). As time passed, it proved its worth in
every corner of the Earth paving way to devise new
methodologies in engineering, hydrology, urban
planning, etc. (Alsdorf et al. 2007; Lehner et al. 2008;
Altunel, 2023). Although rather satisfactory in spatial
positioning and elevation accuracy, they do not provide
enough ground resolution for specialty works. Roughly,
30 m (1 arc-second) spatial resolution in each data
generalizes the average surface facades excessively to
perform precision works. Later, TanDEM-X global DEM
of 12 m (0.4 arc-second) and recently Copernicus
European DEM of 10 m (0.3 arc-second) raised the bar
even further to better represent the surfaces. Although
technology has enabled us to further improve the ground
resolution to even higher levels with UAV and LIDAR
(Akturk and Altunel, 2019; Muhadi et al. 2020), they are
most of time not feasible and easily available
everywhere. Thanks to its long experience of aerial
stereo photo capture, Türkiye recently announced a 5 m
national DEM, which means that it provides 36 and 4
times better earth representation than SRTM and new
Copernicus DEMs, respectively.
In Türkiye, long-time accepted practices for primary
transport are direct tractor skidding, tractor drum
winching and yarders in timber production process. The
major criteria to decide the primary transport method
has been topography of the region and standing volume
to be harvested. For instance, 55% gradient or more
definitely requires special equipment such as yarders
alongside the existing forest road network.
Although the elevation accuracy of a DEM is of the
essence in the first glance, practicality of such a high
resolution DEM highlighted the importance of
topographical parameter extraction (Mukherjee et al.
2013) that is presented in this study as a firm foundation
when deciding what type of logging
equipment/infrastructure might be preferred while
reaching out to the stands to be harvested.

7th Intercontinental Geoinformation Days (IGD) – 18-19 November 2023 – Peshawar, Pakistan
177
2. Method
Kastamonu Regional Directorate of Forestry (RDF)
has been the leading contributor in Turkish timber
production. The study was devised within Daday
Planning Unit in Daday Forest Enterprise (FE) and
coastal Doganyurt Planning Unit in Inebolu Forest
Enterprise, both within Kastamonu RDF to see the
elevation and resulting slope variations (Figure 1). The
existence of treacherous topographies due to coast-
parallel running mountain ranges throughout Inebolu FE
make it a prime candidate for suitable technologies, not
only a forest road network. Besides, inland Daday FE was
also selected because of the existence of a new
generation Tajfun MOZ 500 GR yarder in their machinery
park. Although yarders are the preferred specialized
equipment used in logging when forests on difficult
topographies need to be harvested, they have only been
effectively used in Northeast Türkiye, as if the rest of
Turkish forests were on favorable grounds.
New 5 m national Turkish DEM, produced by General
Directorate of Mapping (GDM), and 2014 geodatabase of
Kastamonu RDF were used. DEM was produced utilizing
the stereo captured air photos. After Yilmaz and Erdogan
(2018) showed over some sample locations placed in
various parts of the country that such a national DEM
could be generated, GDM with its immense stereo air
photography achieve, which have also been used to
produce the topographic maps in various scales for 6
decades, actually attempted and successfully produced it.
DEM was acquired as elevation values reduced to
ortometric heights and projected to UTM-WGS84
projection. DEM was a representation of the land,
through which the slope at any given location could be
calculated. Later, land forms depicted in 5x5 m grid cells
in the DEM were characterized based on the variability of
the slope in their surroundings.
Figure 1. Studied planning units
Topographic roughness is just another topographical
parameter, which can be added to the long list of what
one could produce with an elevation data. Practicality of
it was highlighted in this study because DEMs, especially
the recently introduced high-resolution ones, have
started providing unprecedented detail, which could
easily be translated to whatever is intended.
Topographic roughness is another parameter which
could be calculated over a DEM, showing if the calculated
slope value of a cell is uniform throughout a
neighborhood or not. It could very well define not only
the slope but also how that slope stays the same or
changes in a region (compartments or sub-
compartments in a forestry setting). Given the amount of
how favorably or steeply slope values are assigned to
those 25 m2 DEM cells and how varied those slope values
are, foresters can decide which equipment or
infrastructure might be appropriate to effectively
manage and harvest the forests. To do this, 5 m DEM was
first converted to slope on a projected flat plane using a
2D Cartesian coordinate system, specifying the
inclination of the slope as percent rise. Then, the
resulting slope map was reclassified defining equal
intervals at 1%. Finally, statistics were performed on the
reclassified slope map, using a 3x3 cells configuration,
calculating the slope varieties (the number of unique
values) of the cells within their immediate
neighborhoods. The results showed how each and every
cell in the finalized map was rated in terms of terrain
roughness between 1 and 9 (1-3, rather flat surfaces; 4-6
moderately varied surfaces; 7-9 excessively varied
surfaces), depending upon the changing slope values
(Figure 2). Analyses were performed by using ArcGIS
10.8.
This study was conceptualized on the existence of
both such a DEM, and a known and long-neglected, but
reintroduced new machinery to Turkish forestry, yarder.
Two forest planning units from Daday and Inebolu FEs,
Daday and Doğanyurt were selected based on the
elevation differences acquired by subtracting the lowest
elevation measurement from the highest one (Table 1).
Table 1. Elevation differences within planning units of
Daday and Inebolu and timber production figures of
2022
Forest
Enterprise
Planning
Unit
Production
(m3)
Low
High
Difference
Daday
Karacaoren
900
1640
740
22299
Saricam
820
1519
699
20729
Camkonak
761
1585
824
15331
Camlibel
889
1491
602
12592
Yayla
860
1677
817
15856
Daday
802
1744
942
15212
Ballidag
896
1739
843
18500
Inebolu
Doganyurt
0
1176
1176
8344
Gemiciler
0
687
687
14074
Inebolu
0
415
415
8011
Ozluce
0
1047
1047
9849
Altinkum
0
400
400
9855

7th Intercontinental Geoinformation Days (IGD) – 18-19 November 2023 – Peshawar, Pakistan
178
Figure 2. 5 m national DEM (a), reclassified slope map at 1% intervals (b), calculated terrain roughness values (c)
Both Daday and Doganyurt planning units yielded the
highest elevation differences among the others in their
respected FEs.
3. Results and Discussion
5 m national DEM custom tailored to Daday and
Doganyurt planning units’ administrative forestlands
produced the following acreages. When investigated
through the current Kastamonu RDF geodatabase, it was
observed that Daday and Doganyurt planning units
spanned over 16808 ha and 10228 ha land areas,
respectively. Compared to Daday’s moderately
expanding land area over 55% gradient, 13.2 %,
Doganyurt’s land area amassed 41.4 %, which was rather
steep in a considerably less administrative domain. 2022
production figures showed that Daday planning unit
almost doubled the amount produced in Doganyurt. One
might think how much of this production was done using
ground skidding and winching, and how much using the
yarder. In either case, a proper and sufficient road
infrastructure is needed for forest management, but a
threshold should not ever exceed if proper
mechanization is simultaneously integrated. No further
detailing was performed, but it was concluded that given
the absence of a yarder, Doganyurt’s forest land area
would have been furnished with forest roads if
production were to continue. Roads were regarded as
techno-ecosystems, which require in-depth analyses of
their would-be effects prior to laying them down (Lugo
and Gucinski, 2000). Jordan et al. (2010) stated that risk
assessments should be carried out before forest roads
are actually placed especially in steep topographies.
Thanks to the high-resolution, such assessments could
surely be considered and evaluated through the 5 m
national DEM, because 5 m width and length of a cell
could perfectly align with the proposed road platform of
a type-B forest road, and upslope and downslope areas
around the platform could be further investigated before
the actual road construction begins.
We also checked how the slope values of each 5 m cell
varied with respect to the neighboring ones. Grohmann
et al. (2010) defined the topographic roughness as a
representation of the variability of topographic surfaces,
e.g. changing slope values in the surfaces expressed in 5
m cells in this study. DEMs are used to extract numerous
topographic parameters (Woodrow et al. 2016; Kruk et
al. 2020). High resolution in DEMs provided improved
flood inundation predictions (Saksena and Merwade,
2015). We calculated both topographic roughness
acreage (ha) and percentage (%) for Daday and
Doganyurt planning units (Table 2).
Values affirmed the hardship experienced in
Doganyurt with respect to those displayed for Daday.
Difficult topography might require specialized
equipment to do logging and timber production.
Depending upon the findings materialized in this study,
there must be many planning units across the country
seeking more than ground skidding and excessively and
unnecessarily built forest roads to manage their forests.
It is also obvious that the new 5 m national DEM of
Türkiye is more than capable of producing detailed
topographical works, which were impossible to
accomplish in the past.
Table 2. Topographic roughness acreage and percentage
by planning units
Planning
Unit
Flat
surfaces
Moderately
varied
surfaces
Excessively
varied
surfaces
Doganyurt
ha
162
1684
8382
%
1.6
16.4
82
Daday
ha
2102
4690
10016
%
12.5
28
59.5
Acknowledgement
We thank Kastamonu Regional Directorate of
Forestry and General Directorate of Mapping for
supplying their valuable data.

7th Intercontinental Geoinformation Days (IGD) – 18-19 November 2023 – Peshawar, Pakistan
179
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