Comparison of DSMs Generated Using High Resolution UAV Images in an Archaeological Site

Unmanned Ariel Vehicles (UAVs) are increasingly used for topographic mapping. The use of UAVs in the photogrammetric survey of archaeological sites provides extensive opportunities for the creation of documentation. By using this technology, a detailed and precise digital map of historical and cultural areas can be produced, digital terrain model, orthophotos of the whole area can be produced and inaccessible parts of the historical area such as towers, walls, steep slopes can be documented. For this study, 542 high-resolution images were captured with a UAV from approximately 20 m high. The high-resolution images were processed using Agisoft Photoscan and Pix4Dmapper Pro software to generate point clouds and Digital Surface Models (DSMs). Both software packages produced GSD values are between 0,401 - 0.425 cm/pixel. When comparing the cross sections obtained from the DSMs obtained from the two software packages, it was seen that the Pix4D software was more successful, especially in the sections produced from surfaces, such as ducts and pits

UAV Based Agricultural Planning and Landslide Monitoring

Unmanned Aerial Vehicle (UAV) is finding a wide application field in areas such as map production, land survey, landslide, erosion, agricultural activities, and forest fires monitoring. In this study, an UAV equipped with SONY 6000 camera was used. The flight plan was prepared from 100 m height, and having 80% overlap and 60% sidelap rates. GNSS geodetic receivers and Ground Control Points (GCPs) were observed. GNSS signals were processed with LGO V.8.4 software to receive precise location information. 291 photographs for 50 hectares of landslide area were taken by UAV. All photos were processed by PIX4D software. In the field of the landslide area, 8 GCPs were included in the evaluation. 3D model were produced with pixel matching algorithms. Six period flights in different months were made for the landslide area and ground movements between the periods were observed. During this time interval , the volume of moving soil was determined. At the end of the study, RMSE for soil movement was obtained ±1.79 cm for landslide area. This study demonstrates that UAV-based high resolution orthophoto, 3D terrain model and point cloud data sets can be used to monitor the landslide, especially in micro small areas. It also was revealed that this method has some advantages over other traditional geomatics methods

Kriging yönteminin geoit modellemesinde kullanılabilirliğinin araştırılması

The geoid is a representation of the surface of earth that assumes the sea is covered the earth, also known as surface of equal gravitational attraction and mean sea level. The main function of the geoid in geodesy is to serve as a reference surface for leveling. The elevation measured by leveling is relative to the geoid. Three dimensional coordinates that are easily obtained by GPS easily; are widely used in such applications as large-scale map production and engineering applications. The latitude and longitude values obtained by GPS are used directly, but ellipsoidal height (h) values must be transformed into orthometric heights (H). In many surveying and engineering applications, orthometric heights are required. Ellipsoidal heights have geometric meanings in practical surveying, engineering, and geophysics and in other applications, and they bear no physical meanings. For the transformation from ellipsoidal heights to orthometric heights, which are used in applications, geoid heights (N) must be known with required accuracy. Several techniques can be used for determination of geoid heights. Most commonly used method for the determination of geoid is the combination of GPS data and leveling measurements. The by laws for large scale map production is required to be changed and allow to GPS applications, as parallel to the augmentation in application of the GPS technique. The new draft bylaw contains observation and calculation methods for obtaining orthometric heights by GPS, as well. One of them is determining the height of the geoid by GPS/Nivelman method. In this study, compared with classical methods by the deterministic and Kriging interpolation methods for determining the geoids by GPS/Nivelman method in Istanbul Metropolitan Surface deterministic and Kriging interpolations were calculated by known geoid undulation (NMEASURE) values performed by using ArcGIS 8.3 Geostatistical Analyst software. Geostatistical Analyst provides deterministic and geostatistical interpolation methods. Deterministic interpolation techniques (inverse distance weighted, radial basis functions, and local polynomial interpolation) should not be used for decision making, because they do not provide information on how good their predictions are. Geostatistical interpolation techniques (e.g., kriging) can be chosen based on the result of exploratory spatial data analysis and diagnostics (cross validation and validation). Deterministic methods use predefined mathematical functions for interpolation. Geostatistical methods rely on statistical features of the data. Geostatistical Analyst provides the necessary tools for data exploration and variography analysis. Kriging is based on the assumption that the parameter being interpolated can be treated as a regionalized variable. A regionalized variable is intermediate between a truly random variable and a completely deterministic variable in that it varies in a continuous manner from one location to the next and therefore points that are near each other have a certain degree of spatial correlation. Kriging is a set of linear regression routines which minimize estimation variance from a predefined covariance model. This method uses variogram to express the spatial variation, and it minimizes the error of predicted values which are estimated by spatial distribution of the predicted values. Besides, while the Geoid Model was forming; the effect of control point frequency to computed geoid height values was investigated. To study the effect of point frequency to the counting of geoid, geoid surfaces were formed with 50(~one point to 100 km2), 200(~one point to 25 km2), 393 (~one point to 13 km2) and 434(~one point to 12 km2) points in Istanbul. For testing with interpolations, 50 test points were chosen and NCALCULUS values were counted by various deterministic and geostatistical interpolations. NCALCULUS-MEASURE distinction values were found by subtracting NCALCULUS values from measurement values that were found by NGPS/NİVELMAN method. Mean square errors and maximum, minimum and mean error values were calculated for all methods. By comparing of these values, the method that gives the most suitable surface was chosen. It was found that the results of determining geoid by Kriging method were more precise than deterministic methods. The results of Ordinary Kriging method were more precisely than Simple Kriging method’s results but the maps produced by Simple Kriging method were more esthetic than the other equal geoid height maps. The results found by multiquadratic method between deterministic methods were close to the results found by Kriging method and multiquadratic method gave the best results. For increasing precession augmentation of survey quality is better than augmentation of model points.  Keywords: Geostatistic, deterministic, interpolation, geoid. Geoit, ağırlık potansiyelinin sabit olduğu ortalama deniz yüzeyine yakın bir yüzeydir. GPS ile bulunan enlem ve boylam değerleri doğrudan kullanılmakta ancak elipsoidal yükseklik (h) değerlerinin ortometrik yüksekliğe (H) dönüştürülmesi gerekmektedir. Dönüşüm için yeterli doğrulukta geoit yüksekliklerinin bilinmesi gerekmektedir. Geoit yükseklikleri belirleme teknikleri içerisinde en yaygın kullanılanı GPS/Nivelman tekniğidir. BÖHHBÜY dönüşüm için yerel GPS/Nivelman geoidi kullanılmasını öngörmektedir. Bu çalışmada, İstanbul Metropoliten alanlarında GPS/Nivelman yöntemi ile geoit belirlemek için deterministik ve Kriging enterpolasyon yöntemleri karşılaştırılarak, Kriging yönteminin geoit yüzeyi modellemesinde kullanılabilirliğinin araştırılması yapılmıştır. Uygulamada, ArcGIS 8.3 Geostatstical Analyst yazılımı kullanılmıştır. Dayanak nokta yoğunluğunun geoit hesabına etkisini araştırmak için İstanbul’ da 50 (~ 100 km2’ye bir nokta), 200 (~ 25 km2’ye bir nokta), 393(~ 13 km2’ye bir nokta) ve 434 (~ 12 km2’ye bir nokta) noktalı geoit yüzeyleri oluşturulmuştur. Test için 50 nokta seçilmiş ve bu noktaların deterministik ve geoistatistik enterpolasyonla NHESAP değerleri hesaplanmıştır. NHESAP-ÖLÇÜ fark değerlerinden, farkların maksimum, minimum ve ortalama değerleri ile karesel ortalama hatalar karşılaştırılarak en uygun yüzeyi veren yöntem seçimi yapılmıştır. Çalışmalar sonunda, Kriging yöntemi ile geoit belirleme sonuçlarının deterministik yöntemlerden daha presizyonlu olduğu, Ordinary Kriging yönteminin Simple Kriging yönteminden bulunan sonuçlardan daha presizyonlu olduğu saptanmıştır. Multiquadratik yöntemle bulunan sonuçların Kriging yöntemlerinden bulunan sonuçlara çok yakın olduğu ve multiquadratik yöntemin en iyi sonucu veren deterministik yöntem olduğu, presizyonu arttırmak için nokta yoğunluğunu arttırmaktan çok veri kalitesini arttırmak gerektiği saptanmıştır.  Anahtar Kelimeler: Geoistatistik, deterministik, enterpolasyon, geoit

CBS ile Yeşilırmak Nehir Yatağı Tokat merkez bölümünde deprem riskinin irdelenmesi

Tokat province was established hundreds years ago and has rapidly grown since 1960’s. In spite of being on the first degree of  earthquake zone, the planning and application facilities have not been maintained parallel to the growing and the lands, which is not suitable for settlements, have been used to consruct public or commercial buildings. One of the misused lands is the riverbed of Yeşilırmak in Tokat province city centre. In this study, land use changes in this area have been determined and interpretated in terms of earthquake by using GIS and RS. For this purpose, firstly, the areal photograph taken in 1963 and one meter high resolution satellite image sensed in 2001 by IKONOS of study area were obtained. Secondly, areal photograph of study area has been scanned and coordinated by using georeferencing process in ArcMap software according to the coordinates of satellite image which has been geometricly corrected in the previous studies. After geometric correction of aerial photograph of study area, the shore line of riverbed has been vectorized as a line object by hand digitizing method. And then shore line data, counterlines (in 20 m), geological map, digital elevation model derived from counterlines and satellite image have been overlayed. As a result, it has been concluded that, the shore line’s positions of old riverbed is different than the former. Nowadays, there are more public, commercial and official buildings in this area. For this reason, some measures should be taken, before earthquake comes.Keywords: GIS, RS, riverbed, earthquake, Tokat Province.Bu çalışmada Tokat ilinin bir kısmının üzerinde kurulu olduğu Yeşilırmak Nehir Yatağı’nın eski ve yeni kullanım durumu CBS ve UA olanakları kullanılarak karşılaştırılmış ve deprem açısından değerlendirilmiştir.  Bu amaçla Yeşilırmak Nehri’nin ulaşılabilen en eski hava fotoğrafı (1963) ve Tokat İl merkezine ait 2000 ocak ayı IKONOS uydu görüntüsü ile çakıştırılarak karşılaştırma ve yorumlama yoluna gidilmiştir. Sonuç olarak 1963 yılında kesinlikle ırmak yatağı olduğu görülen yerlerde yoğun bir şekilde  yapılaşmanın oluştuğu ve deprem açısından sakıncalı olduğu ve dolayısıyla  gerekli tedbirlerin alınması önerilmiştir.    Anahtar Kelimeler: CBS, uzaktan algılama, nehir yatağı, deprem,Tokat

Uloga bespilotnih letjelica u praćenju naglih pojava klizišta

This study used an unmanned aerial vehicle (UAV) that was designed and produced to monitor rapidly occurring landslides in forest areas. It aimed to determine the location data for the study area using image sensors integrated into the UAV. The study area was determined as the landslide sites located in the Taşlıçiftlik campus of Gaziosmanpaşa University, Turkey. It was determined that landslide activities were on going in the determined study area and data was collected regarding the displacement of materials. Additionally, it was observed that data about landslides may be collected in a fast and sensitive way using UAVs, and this method is proposed as a new approach. Flights took place over a total of five different periods. In order to determine the direction and coordinate variables for the developed model, eight Ground Control Points (GCPs), whose coordinates were obtained using the GNSS method, were placed on the study area. In each period, approximately 190 photographs were investigated. The photos obtained were analyzed using the Pix4D software. At the end of each period, the Root Mean Square and Ground Sample Distance (GSD) values of the GCPs were calculated. Orthomosaic and digital surface models (DSM) were produced for the location and height model. The results showed that max RMS=±3.3 cm and max GSD=3.57 cm. When the first and fifth periods were compared, the highest spatial displacement value ΔS=111.0 cm, the highest subsidence value Δh=37.3 cm and the highest swelling value Δh=28.6 cm were measured.U ovom radu korištena je bespilotna letjelica (UAV) koja je dizajnirana i proizvedena za potrebe praćenja nagle pojave klizišta u šumskim područjima. Njezin cilj je određivanje podataka o lokaciji područja istraživanja koristeći slikovne senzore ugrađene u UAV. Područje istraživanja je lokacija klizišta u kampusu Taşlıçiftlik Sveučilišta Gaziosmanpaşa, Turska. Utvrđeno je da se klizišta stalno pojavljuju u području istraživanja, a podaci su prikupljeni na temelju pomaka materijala. Osim toga, ustanovljeno je da se podaci o klizištima mogu prikupljati brzo i precizno koristeći UAV, te je ta metoda predložena kao novi pristup. Letovi su obavljeni kroz pet različitih razdoblja. Kako bi se utvrdile varijable smjera i koordinata za razvijeni model, na području istraživanja, postavljeno je osam stalnih točaka (GCP) čije su koordinate dobivene GNSS metodom. U svakom razdoblju proučeno je otprilike 190 fotografija. Dobivene fotografije su analizirane pomoću softvera Pix4D. Na kraju svakog razdoblja izračunate su vrijednosti Root Mean Square (RMS) i Ground Sample Distance (GSD) za GCP. Ortomozaični i digitalni modeli površine (DSM) izrađeni su za lokacijski i visinski model. Rezultati su pokazali da je maksimalni RMS=±3,3 cm, a maksimalni GSD=3,57 cm. Nakon usporedbe prvog i petog razdoblja, izmjerene su najviša vrijednost prostornog pomaka ΔS=111,0 cm, najviša vrijednost slijeganja Δh=37,3 cm i najviša vrijednost ispupčenosti Δh=28,6 cm

UAV Based Agricultural Planning and Landslide Monitoring

The use of Unmanned Aerial Vehicle (UAV) tools has become widespread in map production, land surveying, landslide, erosion monitoring, monitoring of agricultural activities, aerial crop surveying, forest fire detection and monitoring operations. In this study, GEO 2 UAV manufactured by TEKNOMER equipped with SONY A6000 camera has been used. The flight plan have been performed with 100 m altitude, with 80% longitudinal and 60% side overlapping. Ground Control Points (GCPs) have been observed with Topcon and Trimble GNSS geodetic receivers. Recorded GNSS signals have been processed with LGO V.8.4 software to get sensitive location information. 985 photos have been taken for the 344 hectares the agricultural area. 291 photos have been taken for 50 hectares the landslide area. All photos were processed by PIX4D software. For the agricultural area, 25 GCPs and for the landslide area, 8 GCPs have been included in the evaluation. 3D images were produced with pixel matching algorithms. As a result, the RMS evaluation was obtained as ±0.054 m for the agricultural area and as ±0.018 m for the landslide area. UAV images have indisputable contributions to the management of catastrophes such as landslides and earthquakes, and it is impossible to make terrestrial measurements in areas where disaster impact continues

Determination of 2011 Van/Turkey earthquake (M = 7.2) effects from measurements of CORS-TR network

Turkey is a country that has active fault lines and is prone to earthquake. The positional variations resulted from the Van earthquake (a magnitude of M = 7.2) on 23 October 2011 and were calculated by using data from CORS-TR (Continuously Operating Reference Station network) stations. The GPS data from the CORS-TR stations effected from the earthquake were evaluated by the BERNESE 5.0 software. For calculating the positional displacements in the CORS-TR stations after the earthquake that occurred in Van, the measurements from 16 International GNSS Service (IGS) stations around Turkey, where their coordinates and velocity vectors were considered to be constant at the ITRF2005 datum. The greatest variation was measured from the Muradiye station, which is the closest point to the epicentre of the earthquake. The variation in this station was −42.7 mm in the vertical direction, −60.3 mm in the northern direction and −18.7 mm in the eastern direction

The Role of Unmanned Aerial Vehicles in Monitoring Rapidly Occurring Landslides

WOS: 000440485400003This study used an unmanned aerial vehicle (UAV) that was designed and produced to monitor rapidly occurring landslides in forest areas. It aimed to determine the location data for the study area using image sensors integrated into the UAV. The study area was determined as the landslide sites located in the Talieiftlik campus of Gaziosmanpaa University, Turkey. It was determined that landslide activities were on going in the determined study area and data was collected regarding the displacement of materials. Additionally, it was observed that data about landslides may be collected in a fast and sensitive way using UAVs, and this method is proposed as a new approach. Flights took place over a total of five different periods. In order to determine the direction and coordinate variables for the developed model, eight Ground Control Points (GCPs), whose coordinates were obtained using the GNSS method, were placed on the study area. In each period, approximately 190 photographs were investigated. The photos obtained were analyzed using the Pix4D software. At the end of each period, the Root Mean Square and Ground Sample Distance (GSD) values of the GCPs were calculated. Orthomosaic and digital surface models (DSM) were produced for the location and height model. The results showed that max RMS=+/- 3.3 cm and max GSD=3.57 cm. When the first and fifth periods were compared, the highest spatial displacement value Delta S=111.0 cm, the highest subsidence value Delta h=37.3 cm and the highest swelling value Delta h=28.6 cm were measured