THE POTENTIAL OF AIRBORNE LiDAR for DETECTION A NEW ...earth.esa.int/heritage/2015-events/15m38/Presentations/24_Anca.pdf · previous step to generate initial LRM and applying an

PRINCIPIILE SAR

THE POTENTIAL OF AIRBORNE LiDAR for DETECTION A NEW ARCHAEOLOGICAL SITE IN ROMANIA

ANCA PAULA ESRI Romania

Purpose The potential of airborne LiDAR for detection of archaeological site

Objectives • Develop a methodology for the study of

archaeological sites by using LIDAR technology • A case study for CORNESTI archaeological site

.

Why LIDAR data?

• Mapping of hundreds of square kilometers at once ; • Overview of ancient civilizations organization ; • Archaeological data management in geographical context ; • Analysis and visualization of archaeological data in relation with the

environment.

Presenter

Presentation Notes

Archaeology defines its object The main advantage of GIS lies in the ease of managing and producing spatial data but also in the flexibility of handling enormous samples of archaeological data. of study and methods by reference to two fundamentals variables: time and space.

LiDAR Technology

About LiDAR…

o It is an active remote sensing technique o It uses three basic systems

The laser scanning that measure distances GPS The inertial measurement unit (IMU) for

orientation recording

o Multiple responses o 2.5-3 cm vertical accuracy o Point cloud classified

Platform

Airborne platform and LiDAR sensor

Hawker Beechcraft King Air C90-GTx (INCAS)

Long-Range Airborne Laser Scanner for Full Waveform Analysis RIEGL LMS-Q680i

ACCURACY 20 mm

PRECISION 20 mm

LASER PULSE REPETITION RATE

400.000 kHz

EFFECTIVE MEASUREMENT RATE

Up to 266 kHz and 60° scan angle near infrared

LASER WAVELENGTH Near infrared

SCANNING MECHANISM Rotatting polygon mirror

SCAN PATTERN Parallel scan lines

SCAN SPEED 10-200 lines/sec

UNGHI MINIM ÎNTRE DOUĂ FASCICULE LASER

CONSECUTIVE

Δ𝜗𝜗 ≥0.002°(pentru 400000 Hz)

ANGLE MEASUREMENT RESOLUTION

0.001°

DIMENSIONS 480 x 212 x 230 mm

WEIGHT 17.5 kg

Data and methodology

Cornești-Timiș County

o It is located in the northern part of Timiș County, north of the city.

o The site covers an area of 1780 hectares

o Consists of four concentric rings -They are actually the walls of the fortification

Archaeological site: Cornești

A little bit of history…

• Fortification appears on the first Mercy maps (1723-1725) and then on all military maps by the end of the First World War.

• The first excavations were carried out in 1939 by archaeologist Marius Moga.

• March 2013 – first LiDAR flight

Austro-Hungarian Map locating the fortress from Corneşti , 1723


Trajectories Flight parameters

• Date: 27.06.2014 • Total number of trajectories: 26


Digital Terrain Model and Digital Surface Model

The LiDAR blocks LiDAR point cloud

Removing noise measurement

Digital Terrain Model

Presenter

Presentation Notes

For the purposes of this paper, the digital terrain model from LIDAR data was done using TerraSolid software where generation is automatic and 80% of the whole process is represented by the editing step.

Digital Terrain Model

Automatic generation Manual editing

Reprezentarea 3D a MDT-ului


Results…


Validating the results

Ground control points on topographic map 1:25000

Presenter

Presentation Notes

RMSE- standard deviation

Methods for archaeological investigation

Local Relief Model

LRM is one of the most useful and efficient way to visualize elevation data stored in raster as digital elevation model

The basic idea behind the method

is „filtering out” terrain surface leaving just archaeological features and their relative elevation above or below the terrain.

A GIS model

Presenter

Presentation Notes

Visualization of elevation data [8] collected by aerial laser scanning for archaeological use is a widely discussed topic. Every method has its advantages and disadvantages in usability, efficiency, time consumption. It is obvious that simple shaded relief model (hillshade) is not sufficient for archaeological research and there are much better ways of visualization. Local relief model [9] (LRM) is one of the most useful and efficient way to visualize elevation data stored in raster as digital elevation model (DEM). The basic idea behind the method is „filtering out” terrain surface leaving just archaeological features and their relative elevation above or below the terrain. The simplest way to do so is to generalize DEM by low pass filter and substract it from original DEM [10]. In order to automate all the steps for LRM generating of the study area, a model builder was used in ArcGIS software, 10.3 version.

1. Filtering Applying the first low pass filter „smoothing 5x5” twice for DTM

Applying the second one with a 15 m kernel size


Presenter

Presentation Notes

Processing steps of the digital terrain model to obtain local relief model are the following: Applying the first low pass filter „smoothing 5x5” twice for DTM (the data was smoothed by reducing local variation and noise removing) and then applying the second one with a 15 m kernel size and a circular neighborhood to approximate large scale landforms (this size has been found experimentally to be the most suitable to represent especially the first two walls of the fortress).

2. Local Relief Model


Calculating the difference between the original raster and the resulting one in the previous step to generate initial LRM and applying an appropriate color scheme.

Presenter

Presentation Notes

Calculating the difference between the original raster and the resulting one in the previous step to generate initial LRM and applying an appropriate color scheme.

• Extracting contour lines • Selecting the zero contours • Converting these contours into points • Extracting the elevation values

3. A “clean” digital terrain model


• Interpolating the elevation values

Presenter

Presentation Notes

5. Extracting contour lines for the filtrated raster (the boundaries between positive and negative features of the local landscape were delineate in order to determine which positions are zero raster values); selecting the zero contours (meaning the limits of small scale positive and negative topographic characteristics); converting these contours into points and extracting the elevation values. 6. Creating a purged dem by interpolating elevation values generated in the previous step (this raster represents the large-scale landforms that will be removed to expose the local topography in the final step).

4. The final LRM


Presenter

Presentation Notes

Calculating the difference between the original raster and „purged” DEM to get the final LRM and applying an appropriate color scheme.

5. Raster binarization


• Raster binarization by applying the „percentage threshold" method

• Select the cells with value 1 • Convert them in polygons • Manual editing of them in order to keep

only the polygons of interest.

Hillshade


Conclusions

• The benefits of using LiDAR technology in archaeological investigations by generating DTM, DSM and LRM and analyzing the results.

• The main advantage of this technique is the full automation process: run a GIS model

Presenter

Presentation Notes

Through this study case, it has been shown the benefits of using LiDAR technology in archaeological investigations by generating DTM, DSM and LRM and analyzing the results. The main advantage of this technique is the full automation of the aquisition process, storage and processing of data based on specialized programs, finally leading to a set of geographic spatial information, as the possibility of laser beam to penetrate the vegetation up off the ground, essential feature for the activity of archeology. The particularities of relief, printed through altitude, favor the development of different sub-areas, therefore different analyzes using combined technoques (DTM, DSM and LRM’s generation) can be made. The aerial images also provide a range of advantages in archaeological investigation: high resolution, georeferencing in national projection system (Stereographic 1970) and the possibility of multiple analyzis using GIS programs.

THANK YOU!

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THE POTENTIAL OF AIRBORNE LiDAR for DETECTION A NEW ...earth.esa.int/heritage/2015-events/15m38/Presentations/24_Anca.pdf · previous step to generate initial LRM and applying an