Possibilities of Utilizing New Very High Resolution DEM in Turkish Forestry

Abstract

Türkiye has come a long way since the introduction of first nationwide topographic map coverage in 1959-60. Since then, many distinctly scaled topographic, geologic, administrative, etc. maps have been produced and put into service with the interested parties, domains and projects. Due to including considerable amount of surface and land-cover detail, 25000 scaled topographic maps have been at the forefront of many scientific and infrastructure related works. Topographic maps have always been produced through stereo air-photo based photogrammetric techniques. Since the fourth quarter of the 2000s and along with the advancing technology, map production from the air-photo capture to the final digital raster product has entirely turned to digital means and capabilities. Thus, one last addition to the long list of successful cartographic accomplishments carried out by the General Directorate of Mapping has been introduced as the new 0.3 m national baseline digital elevation model (DEM). The initial visual investigation of this unusually high-resolution new DEM has revealed that it might open new horizons in various disciplines such as cadastral planning, agriculture, forestry, natural disaster mitigation, national defense, etc. In forestry particularly, forest management, watershed management and transport planning activities might benefit from this data. In this study, the usage possibilities of this new 0.3 m baseline DEM in Turkish forestry were elaborated through visual comparisons that had been captured from related domains within the raster DEM.

Full text

VIII. INTERNATIONAL HALICH CONGRESS ON MULTIDISCIPLINARY
SCIENTIFIC RESEARCH
December 3-5, 2024, ISTANBUL
THE BOOK OF FULL TEXTS
Volume-1
Edited by
Prof. Dr. Muhittin ELİAÇIK
Gulnaz GAFUROVA
ISBN: 978-625-378-037-1

POSSIBILITIES OF UTILIZING NEW VERY HIGH RESOLUTION DEM IN
TURKISH FORESTRY
Arif Oguz ALTUNEL
Assoc. Prof. Dr., Kastamonu University, Faculty of Forestry, Kastamonu, TÜRKİYE
Oytun Emre SAKICI
Assoc. Prof. Dr., Kastamonu University, Faculty of Forestry, Kastamonu, TÜRKİYE
Samet DOGAN
Lecturer, Kastamonu University, Ihsangazi Vocational School, Kastamonu, TÜRKİYE
ABSTRACT
Türkiye has come a long way since the introduction of first nationwide topographic map
coverage in 1959-60. Since then, many distinctly scaled topographic, geologic, administrative,
etc. maps have been produced and put into service with the interested parties, domains and
projects. Due to including considerable amount of surface and land-cover detail, 25000 scaled
topographic maps have been at the forefront of many scientific and infrastructure related works.
Topographic maps have always been produced through stereo air-photo based photogrammetric
techniques. Since the fourth quarter of the 2000s and along with the advancing technology, map
production from the air-photo capture to the final digital raster product has entirely turned to
digital means and capabilities. Thus, one last addition to the long list of successful cartographic
accomplishments carried out by the General Directorate of Mapping has been introduced as the
new 0.3 m national baseline digital elevation model (DEM). The initial visual investigation of
this unusually high-resolution new DEM has revealed that it might open new horizons in
various disciplines such as cadastral planning, agriculture, forestry, natural disaster mitigation,
national defense, etc. In forestry particularly, forest management, watershed management and
transport planning activities might benefit from this data. In this study, the usage possibilities
of this new 0.3 m baseline DEM in Turkish forestry were elaborated through visual comparisons
that had been captured from related domains within the raster DEM.
KEYWORDS: Digital elevation models, Forestry, Land management, Transport planning
INTRODUCTION
In line with the technology of the time, surface representation in Türkiye, as well as in the rest
of the World started with the hard-copy production of topographic maps released in various
scales. Although the advancing technology and the capabilities has nullified the use of such
hard-copy maps, their land-cover and elevation precisions have not changed owing to the strict
photogrammetric approaches used in their making (Altunel and Sakıcı, 2023). Especially after
the 1980s as the cartographic capabilities have started leapfrogging, they have long been ready
to be digitized and used to depict the topography and the related derivatives in various studies
and projects (Carter, 1988; Arrighi and Soille, 1999; Freudiger et al. 2018). Until the release of
C-band based and X-band based Shuttle Radar Topography Mission (SRTM) digital elevation
models (DEM) in the second half of the 2000s, they were practically the only solution to turn
to when topographic parameters were concerned. Stereo air-photo capture and photogrammetric
principles were key in their success, so that Öztürk and Koçak (2007) later showed that not only
the topographic maps, but also a very popular secondary product, a national DEM, could very-
well be produced using the digitally acquired stereo air-photography. Indeed, such a product
with an unusually high spatial-resolution of 5 m, was released by the General Directorate
Mapping (GDM) as early as the end of 2023 (GDM, 2024). Altunel and Doğan (2024) showed
8th INTERNATIONAL HALICH CONGRESS ON MULTIDISCIPLINARY SCIENTIFIC RESEARCH
www.izdas.org/halic Istanbul, Turkiye
282

that a rather consistent less than 2.5 m Root Mean Square Error (RMSE) and Mean Absolute
Error (MAE) could be achieved through this DEM. Although this new 5 m national DEM along
with the Airbus DS Geo GmbH’s famous 12 m TanDEM-X based TREx DEM, have been
available to the interested parties via official-contract in GDM’s products portal, the underlying
dataset that the above-mentioned new high-resolution DEM was depended upon and produced
as a 5 m resampled secondary product, was the subject of this study, 0.3 m national baseline
DEM. After Yılmaz and Erdoğan (2018) showed how digitally acquired stereo air-photos could
be auto-correlated to produce almost LiDAR quality DEMs, GDM has managed to produce this
baseline DEM using the recently acquired, 2020-onwards, digital stereo air-photos. Just like the
popular global land-cover datasets that are continuously updated (Altunel and Çelik, 2023), if
the quality of this baseline DEM is good and it will also be updated with new air-photo
acquisitions, it could very well provide a high-quality topographic data for Türkiye for years to
come.
DATA
To understand the level of detail that can be achieved in this baseline DEM, Figure 1 was
devised.
Figure 1. Illustration of the baseline DEM spatial resolution with respect to the others
PROSPECTS OF WHAT CAN BE DONE USING THE BASELINE DEM
Precision of the baseline DEM can be checked with extensive GNSS leveling if not already
present in GDM, itself. With the amount of accumulated such leveling records in hand, we will
surely perform that check by simultaneously comparing it to the global DEM datasets such as
Copernicus, FABDEM, Diluvium DEM, etc. Especially in the case of Diluvium DEM, it can
shed light to coastal deformations.
8th INTERNATIONAL HALICH CONGRESS ON MULTIDISCIPLINARY SCIENTIFIC RESEARCH
www.izdas.org/halic Istanbul, Turkiye
283

Owing to the amazing detail, it appeared that Above Ground Biomass (AGB) calculations can
be done if a proper Digital Terrain Model (DTM) generating algorithm is run over the baseline
DEM because individual trees are perfectly visible within the dataset. Additionally, it appeared
that the tree heights could also be measured (Figure 2).
Figure 2. Tree forms are just like what to be expected from photogrammetric stereo air photo
interpretation
Unusually intricate surface detail could be very handy in hydrological studies such as snow and
avalanche management and mitigation, surface water and mass movement channeling, volume
calculations etc. (Figure 3).
The only restrictive side of the baseline DEM is the fact that each dataset is custom tailored to
the frame of the corresponding 25000-scaled topographic map. Since the amount of the detail
in each frame is considerably enlarging the individual file size, it will be rather difficult to
handle more than one frame because the processing capabilities in our disposal are relatively
weak to work on an entire province spanning large number of frames. As we learned through
the correspondence that we established with the GDM, although publicized as the baseline data
underneath the new national 5 m DEM, their production sequence is still continuing so the
demands may not be immediately filled.
8th INTERNATIONAL HALICH CONGRESS ON MULTIDISCIPLINARY SCIENTIFIC RESEARCH
www.izdas.org/halic Istanbul, Turkiye
284

Figure 3. Rather detailed surface representation
CONCLUSION
It is a remarkable feat that the GDM has managed to produce such a datasets for Türkiye and
its peoples’ endeavors. The absence of LIDAR technology and more than 70+ years of stereo
air-photo capture and photogrammetry know-how has probably forced the GDM to opt for this
way. It sure looked promising, but despite the amazing spatial resolution, it would still stay
behind what aerial LIDAR can do.
REFERENCES
Altunel, A. O., & Celik, D. A. (2023). Sentinel-2 derivatives are rewriting land-cover history.
Advanced Engineering Days (AED), 6, 83-85.
Altunel, A. O., & Sakıcı, O. E. (2023). Topografik harita üretim tekniklerine ilişkin yükseklik
hassasiyetlerinin arazi örtüsü tipi bağlamında karşılaştırılması. Anadolu Orman
Araştırmaları Dergisi, 9(2), 22-32. (in Turkish)
Arrighi, P., & Soille, P. (1999). From scanned topographic maps to digital elevation models.
Proceedings of Geovision, 99, 1-4.
Carter, J. R. (1988). Digital representations of topographic surfaces. Photogramm. Eng. Remote
Sens., 54(11), 1577-1580.
Freudiger, D., Mennekes, D., Seibert, J., & Weiler, M. (2018). Historical glacier outlines from
digitized topographic maps of the Swiss Alps. Earth System Science Data, 10(2), 805-
814.
GDM (2024). Harita Genel Müdürlüğü, Yükseklik Verileri (GRID). Available through
https://www.harita.gov.tr/urunler/yukseklik-verileri-grid/1, accessed in 25.11.2024.
Öztürk, E., & Koçak, E. (2007). Farklı kaynaklardan değişik yöntem ve ölçeklerde üretilen
sayısal yükseklik modellerinin doğruluk araştırması. Harita Dergisi, 137, 25-41. (in
Turkish)
Yılmaz, A., & Erdoğan, M. (2018). Designing high resolution countrywide DEM for Turkey.
International Journal of Engineering and Geosciences, 3(3), 98-107.
8th INTERNATIONAL HALICH CONGRESS ON MULTIDISCIPLINARY SCIENTIFIC RESEARCH
www.izdas.org/halic Istanbul, Turkiye
285