These days it is common that we see surveying and mapping professionals using unmanned aerial vehicle (UAVs) for surveying heritage sites, map roads or terrains. Collecting information from the skies has been an approach in practice since long, but the expenses related with traditional manned aircraft makes the effort extremely costly. UAVs offer a cost operative substitute with far more flexibility of being able to get into the air quickly and without requiring a logistical support. UAVs also help in improving data collection accuracy & efficiency and optimize workflow. In a simple context, UAVs make it far easier to collect the information required to create maps by reducing the overall costs and streamlining the image-capturing process.
ADCC recently completed 2 different projects successfully, one in Mining and one in Heritage mapping.
Project 1 – Terrestrial Laser Scanning Of Nagardhan Fort
Cultural Heritage is acknowledged as a precious asset of human being, which depicts its accomplishments over centuries. The need for documentation and conservation of cultural heritage is well understood and specialists attempt is to exploit all possible methods to fulfil this objective. There are several published works and papers, which put emphasis on the significance of the documentation of the cultural heritage locations. However, with new innovations in tools and technologies and the evolving human race, the original concept of the conservation of cultural heritage has changed substantially. The new technologies such as computers and digital tools have opened new doors and unleashed new opportunities in the process of conserving the cultural heritage. Hence, it is important to review different technologies in order to make the best advantage of these tools in the cultural heritage field.
ADCC carried out a Pilot Project on Nagardhan fort 3D modelling using Laser Scanning. The project was carried out in two phases TLS survey and Data Processing. TLS Survey was carried out in two days and further one day for data processing. The final results were generated over a period of 60 man hours.
Purpose of this Project was to check the accuracy and efficiency of LiDAR scanning and to prepare a 3D model of Nagardhan Fort.
Nagardhan Fort is situated 38 kms northeast of Nagpur and about 9kms south of Ramtek, in an old town founded by a Suryavanshi King.
Latitude: 21.3437 | Longitudes: 79.317
Usage of GIS based services
Terrestrial Li-DAR: FARO Laser Scanner Focus3D
- Distance accuracy up to ±2mm
- Range from 0.6m up to 130m
- HDR photo overlay
- HD photo resolution up to 165 megapixel colour.
01. Architectural Drawing
02. 3D Model
03. 3D Walkthrough
After successful completion of the pilot study we learned the following about Laser technology:
- LiDAR technology can be implemented for Heritage sites preservation projects.
- 3D data can be easily converted into 2D Drawings.
- Data Acquisition and Data Processing is faster and saves time.
- Architectural Significance can be highlighted.
- Integration with CAD to generate map.
- LiDAR can be operated in both Day and night operation is an added advantage.
- Data can be preserved for a long time since it is available in digital format.
The application of various UAV technologies for metric documentation of cultural heritage confirms the array of appropriate choices for documentation of an object. However, a single method cannot guarantee the desired accuracy and there are always obstacles and problems, which limit the capabilities of a technique. Cost, time, complexity and size of the object itself, accessibility, the skill of the survey team etc. play an important role in selecting a survey method. Each single method has its own particular characteristics. Nevertheless, in most cases, a single method cannot be responsive to the requirement of a project and it is needed to exploit a combination of different techniques to achieve the desired result. This hybrid approach is best possible method for documenting cultural heritage.
Project 1 – Kandri Mine Survey using Terrestrial Laser Scanning for Maharashtra Remote Sensing Application Centre, Nagpur
This report has been prepared by ADCC Infocad Private Limited for Maharashtra Remote Sensing Application Center, Nagpur to introduce new high density volume calculation using Terrestrial Laser Scanner (TLS) with the help of a pilot project. The pilot project was successfully carried out in two phases i.e. TLS Survey and data processing which took four days from April 03, 2014 to April 06, 2014 at Kandri Mines MOIL, Mansar. TLS Survey was carried out in two days and further two days were carried out for data processing. The total field work include 3 hrs for target planning on site and 5hrs for scanning (including scanning time of 2 hrs and rest for moving around the field and setting up instruments). Initial data processing for a presentation at the site was completed within 8 hrs. The final results presented in this report were generated over a period of 20 man hours.
The results covered various aspects and advantages of laser scanning technology over mine survey. The data collected during pilot project at Kandri Mines were shown during the presentation along with the outputs generated, e.g. contour plot, longitudinal and transverse profiles, 3D visualization, computed volume of the open cast pit etc.
This report has been prepared by ADCC Infocad Private Limited for Maharashtra Remote Sensing Application Center, Nagpur to introduce a new high density volume calculation using Terrestrial Laser Scanner (TLS). The following objectives were set by ADCC for the pilot project to show the capability of the laser scanning technology to MRSAC, Nagpur:
- Complete scanning of open cast pit of around 13 hectares at Kandri Magnesite Mine.
- Estimating the Volume that has been excavated till date.
- Constructing the 3D digital elevation model (DEM) of the entire open case pit
- Generating Mesh Model
- Complete data archiving for future.
Kandri Magnesite Mines which is located around 40km from Nagpur in Maharashtra and the extent of the Magnesite mine is around 13 hectares.
Usage of GIS based services
The pilot project was successfully carried out in two phases i.e. TLS Survey and data processing which took four days from April 03, 2014 to April 06, 2014 at Kandri Mines MOIL, Mansar. TLS Survey was carried out in 2 days and further 2 more days were carried out for data processing. The total field work include 3 hrs for target planning on site and 5hrs for scanning (including scanning time of 2 hrs and rest for moving around the field and setting up instruments). Initial data processing for a presentation at the site was completed within 8 hrs. The final results presented in this report were generated over a period of 20 man hours.
- a) Terrestrial laser scanner
- b) Targets for laser scanning
- c) High end laptop for data processing
- d) Polyworks for initial post-processing of 3D Point Cloud Data
- e) Volume Computation software for volume computation
- Reconnaissance survey was carried out for choosing strategic location for laser scan station and the targets.
- Laser scanning was conducted at five carefully chosen scan stations on the days as shown in Table1. Depending on the station, location and coverage single or multiple scans from one location were performed. This also determined the level of tilt that was maintained for the scans. The scan location, scan duration and number of points captured are given in the following table:
S. No. Scan Station Date Time taken Number of points Average Point spacing 1. At the centre 04.04.14 20 min 60,00,000 2cm 2. At the North face 04.04.14 20 min 61,00,000 2cm 3. At the East face 04.04.14 20 min 45,00,000 2cm 4. At the South face 04.04.14 20 min 50,00,000 2cm 5. At the West face 04.04.14 20 min 45,00,000 2cm
Table 1: Laser Scanning Data Specification
- The scans collected from multiple stations were aligned to generate a complete point cloud of the entire area. Targets were specially analysed and designed by the team for this purpose. The complete point cloud has around 200 million points with an average spacing of 2 cm.
- Individual scans were passed through QA/QC routines to eliminate spurious points.
- Laser scanning data has also captured the above ground objects, e.g. trees, poles, vehicles, wires etc. Further, Bare earth model (BEM) for complete open cast mine pit was generated by removing these above ground objects.
- A mesh model of the open cast pit was generated from the cleaned point cloud.
- Volume computation software was used to compute the volume that has been excavated from the pit over a period of time.
- A contour map was generated at 1 m interval. Due to large data density of highly accurate laser scan points, generating of contour map at smaller contour interval are more suitable.
- Further, 3D visualizations of data were created. This facilitates the interaction with the mining site within one’s office. One can perform armchair surveying of mining site using the models and have an idea of the site from office itself.
- Data are archived and can be used in future.
The results covered various aspects and advantages of laser scanning technology over mine survey. The data collected during pilot project at Kandri Mines were shown during the presentation along with the outputs generated, e.g., contour plot, longitudinal and transverse profiles, 3D visualization, computed volume of the open cast pit etc.
- Volume Computation
By using volume computation software, volume of the open cast mine has been estimated. It allows calculating of volume by different scans over a period of time. The first scan was completed in morning and after some excavation in the surface, the mine is rescanned in the evening to calculate the volume of the excavated area.
- Mesh Model was generated from the point cloud data.
- Digital Elevation Model is the 3D representation of ground surface topography. Laser scanning collects highly accurate 3D coordinates of a large number of densely located points on the surface of mine. This 3D coordinates helps to construct highly accurate DEM. The DEM of the Kandri Mines was made from approximately 200 million points.
The pilot project was successfully carried out at Kandri Magnesite Mines with a presentation at the site with clarification. Entire open cast mine area was surveyed within a day of field work with the scanning time of less than 5hrs. Data processing was carried out for around 24 hrs. The change in volume of the open cast pit was estimated. The following data products were generated from the captured point cloud: Digital Elevation Model, Volume computation results and a video of the mine for 3D visualization.