ANNALS OF DUNAREA DE JOS UNIVERSITY OF GALATI [307481]

ANNALS OF “DUNAREA DE JOS” [anonimizat], [anonimizat] (XXXIX) 2016, No.1

photogrammetric aplications using uav systems

Maxim Arseni1,*, Lucian Puiu Georgescu1, Gabriel Murariu1

1 [anonimizat], “Dunarea de Jos” University of Galati, 111 [anonimizat]-800201, Galati, Romania

*Corresponding author: maxim.arseni@ugal.[anonimizat] (UAV) [anonimizat]. Further, [anonimizat] 3D modelling issues. [anonimizat] a low-cost solution instead to the classical manned aerial photogrammetry. With a [anonimizat] a reasonable way 3D [anonimizat] 3D models, [anonimizat]. [anonimizat], many such devices are capable to perform the photogrammetric data acquisition process. [anonimizat]-automated or autonomous modes in order to succeed in reaching the suited resolution. The present paper presents a review on UAV utilization for geomatics applications.

Keywords: UAV, 3D model, photogrammetry, [anonimizat]. The term of UAV is used frequently in the geomatics literature. Alternative terms are Remotely Piloted Vehicle (RPV), Remotely Operated Aircraft (ROA), Remote Controlled (RC) Helicopter, Unmanned Vehicle Systems (UVS) and Model Helicopter [1].

[anonimizat]. [anonimizat] [2].

The growing demand for these UAV photogrammetry applications led to a significant development for this technology and appliances. [anonimizat]-cost platforms with increasing performances combined with amateur or professional digital cameras and GNSS/INS systems [3, 4 and 5].

Nowadays, the geomatics applications request to navigate the UAV with high precision to the predefined acquisition points at a sharp controlled altitude in order to succeed in reaching the needed photograms at a suitable resolution [3, 4 and 5].

On the other hand there are a series of disadvantages: [anonimizat] [3, 6].

In the last period, a [anonimizat], [anonimizat] [6, 7].

[anonimizat], [anonimizat].

[anonimizat], [anonimizat], volume computation [4, 7]; archaeology and cultural heritage; environmental surveying, traffic monitoring: surveillance; 3D reconstruction;

MATERIALS AND METHODS

The used system included a R3 Robotics X8-M UAV with related software mission planner. (Fig. 1). The planning is easily made starting from the area of interest (AOI), using the ground sample distance (GSD) or footprint, and knowing the specific parameters of the mounted digital camera. Thus setting the image scale and camera focal length, the flying height is than computed [6, 7 and 8].

Fig. 1. Area of interests – “Dunarea de Jos” University Campus

The camera perspective centers (the so called waypoints) are than established by fixing the longitudinal and transversal intersections of the flight strips. During the flight, the existence of GNSS/INS onboard is usually exploited to guide the image acquisition (Fig. 2).

To reach the main purpose of this paper was used an octocopter X8-M (Fig. 3a). The take-off and landing actions are strictly related to the active vehicle and its’ characteristics, but normally the UAV was controlled from ground by a pilot with a remote controller – Spectrum DX7S type (Fig. 3b).

Fig. 2. Overlaps and side laps of footprints (75% x 75%)

During flight, the UAV platform is saw with a specific control station – FPV Diversity RX. The ground control station is capable to show the flight data such as position, speed, attitude and distances, GNSS observations, battery or fuel status, rotor speed, etc. in a real – time data stream (Fig. 3c).

To maximize the time of flight a lightweight Canon Digital S110 compact camera has been selected (Fig. 3d). The effective argument which states the chosen for the Canon S110 camera is the option to run suitable scripts by using the CHDK (Canon Hack Development Kit) [7]. While running the camera on board the UAV such script has been used that takes a series of images with a distinct time interval.

Fig. 3. Used equipment to study the AOI

GENERATION OF 3D POINT CLOUD

The flight mission’ result consists in a series of about 50 images which were acquired over the “Dunarea de Jos” University Campus area of Galati. The flight altitude was 100 m from the ground and the flight speed was 3m/s.

The first step of data processing starts with the selection process of the acceptable images. During this step, which up to now is carried out manually, the images which are rejected should have the following characteristics: a) images that have been taken during take-off and landing; b) images that are blurry, under – or overexposed; c) images that do not cover the area of interest.

Our experience has shown that 20% to 30% have to be eliminated in practice (Fig. 4). The remaining images are then used to generate a 3D point cloud.

Fig. 4. Images acquired during the flight path and textured model

GENERATE ORTHOPHOTOPLAN AND GEOREFERENCED IMAGE

Software

The used software was AgiSoft PhotoScan which is a commercial product [10]. The results from this paper have been processed by using the standard edition. This software can be used under Windows operating systems and could generates 3D point clouds from a series of digital imagery. All data remains with the user as this software can be operated on a local personal computer. For the computation of large projects (starting from 100 images upwards) it is recommended to employ a 64bit operating system with at least 6 GB of RAM [11].

Georeferenced orthophoto image

Once a proper DSM is presented (Fig. 5), the orthoimage construction can be performed. This procedure is widely automated and requires human interaction only for input of parameters such as the area of interest and the resolution of the final result.

Fig. 5. Digital surface model generated by AgiSoft Photoscan

If necessary, the single orthoimages of a photogrammetric block can be mosaicked. Generation of orthomosaics can be more time consuming in case of strong radiometric differences between the input images, which have to be adjusted beforehand.

Direct georeferencing offers the great advantage that no signalization, no local survey of reference points in the field as well as no determination within the point cloud is needed [8]. Direct georeferencing can be achieved by using data from GPS data that’s been recorded during flight [6, 8 and 9].

The obtained orthophotoplan have a superior resolution to those obtained in a conventional manner. The obtained accuracy is of 2cm/pixel or better (Fig.6, Fig.7). The results encourage us to continue this promising research to build a full integrated solution.

Fig. 6. Georeferenced image in STEREO 70 coordinate system (image obtained from UAV system)

Fig. 7. Referenced area of interests (from google image)

CONCLUSION

This paper presents a specific results obtained with an UAV system. The outcome was delivered as a high temporal and spatial resolution image.

The obtained information and representations using such devices allow a rapid response in a series of critical situations where immediate access to 3D geo-information is requested.

In this paper was presented such kind of result gotten with a rotary wing UAV platforms which can even take-off and land vertically. For small-case applications, these UAVs can be a complement or replacement of terrestrial acquisition [13].

References

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https://github.com/ArduPilot/ardupilot/tree/master/Tools/CHDK-Scripts

http://www.agisoft.com/

Murariu Gabiel , Valentin Hahuie, Lucian Georgescu, Maxim Arseni, Adrian Gabriel Murariu and Catalina Iticescu, Study on the influence of atmospheric parameters on the accuracy of the geodetic measurements, accepted in American Institute of Physics – Conference Proceedings