Home Geospatial Applications Archaeology Light plane field observation supporting Remote Sensing data for archaeology purpose

Light plane field observation supporting Remote Sensing data for archaeology purpose

Michiro Dufo Kusanagi
Space Technology Applications and Research Program
School of Advance Technologies, Asian Institute of Technology
Klong Luang, Pathumthani, Thailand
Email: [email protected]

Sompoch Puntavungkour
Map Information Center, Royal Thai Survey Department
Pra-Nakorn, Bangkok, Thailand
Email: [email protected]

Abstract
The satellite data are applied for a variety of many fields including archeology filed however there are some limitations such as the insufficient resolution of the detail for ancient palace reconstruction, the unselected weather etc. To solve that limitation, this paper proposes the new way for a filed observation. The commercial digital CCD camera is mounted with the wing of the light plane based on the principle of the traditional aerial photograph. The digital image is the result from this observation. Also this digital image is the near vertical image to correct the geometry easily in the further processing. For an archeology field such as ancient palace visualized mapping, this proposed method is able to obtain the near vertical digital image, like the traditional aerial photograph and is flexible to process, unlike the traditional aerial photograph as well as is cheaper than the high-resolution image from satellite.

Introduction
More than thirty years has passed since the first Remote Sensing satellite was put into orbit. Remote Sensing, a part of the Space technology had achieved tremendous progress so far partly due to national security and so on. Priority was placed to the challenge and the development of a variety of satellite data. The data are not expensive, high resolution, not weather-limited and not time limited. Exactly Satellite data have been applied in several fields such as agriculture, infrastructure, and military as well as archeology fields.

Satellite Data is used in archeology fields widespread as to detect the vanished ancient city, reconstruct the ruin palace including simulate some minestrone in history. However the satellite data is sometimes limited with its recurrence, expensive cost the weather including insufficient resolution. In some case of the fast reconstruction of the important palace, the satellite data with a high resolution distribute more rough detail of the palace texture and also in a cloudy day the data exist the haze, random noises in the image. To compensate the limitation of the satellite data, the new challenge way, a field observation by integrating the sensor on the light plane have been developed and experience in the field observation as below.


Figure 1 Satellite images with insufficient high resolution and noise

Field Observation
Field data are essential for calibration of satellite data but also very important for supplementing those satellite data. For a global research, satellite image dada itself is sufficient enough for analysis in many cases. Meanwhile for the very local remote sensing application sometime satellite data are insufficient. Visible data for some area is tend to miss due to a cumulus. Southern islands near tropical area are very often covered by thick cloud for a long time.

Data by some other observation methods are desired to augment satellite data if the timeliness has important meaning for the analysis. These local field data are always required for each region to obtain and archive. Now at STAR program simple, affordable and easily transportable platform technologies are under investigation. Some were field- tested and had show excellent performance but for some limited weather conditions.

Flying Observation Platforms
The most powerful measure next to or even exceeding in some sense to the Earth Observation Satellite is the aerial photometry by surveillance aircraft or helicopter. The system had fully matured and highly dependable but a little expensive and less with mobility. Utilization of dirigibles or airships is suited for continuous long duration observations over specified area. Some systems are commercially available but still expensive and not suited for rainy or windy days. For the similar weather conditions very mobile and inexpensive platform is available using for sky sport light planes. Cost, transportability and space for take off and landing a para plane has advantage though a little sensitive to winds. Similar performance but with much stability are with ultralights. Further explanation of this system with some results is given in next paragraph.

For more local area, much challenging systems with radio control helicopters and airplanes are introduced and has demonstrated its usefulness (Chiba University etc.).

Another system with further inexpensive and yet longer mission time is obtainable by using tethered system such as balloons and kits. Critical components such as a stabilized platform, RF command and telemetry subsystems are under investigation to consist a powerful element of the field observation terminals.

From the practical and operational point of view, continuous monitor over all weather condition is desired especially for disaster monitoring. Next generation observation satellite might give answer to this challenging problem. The most practical and feasible approach with existing technology is in the selection of system case by case. Common to each system are the mobile ground data handling terminal for quasi real time data evaluation and transmittance. These are the part of network and data system concept of next section

System Using Ultralight


Figure 2 Tested Ultralight Platform and the plan in Three Views

As an image capture device Ricoh RDC-7 color digital CCD camera was mounted on the left side strut just below the sheet with shock absorbing material in between. Flight was about 60 minutes over the out skirts of Chonburi City on the cloudy day at the height of about 500-m with the speed of around 45 km/hr.


Figure 3 a test digital CCD camera (Ricoh model RDC-7)

The picture was taken every 30 seconds. Although focus are not sharp as a picture taken on ground, the quality of pictures were fine as shown in the Fig.5 and sufficient enough for most applications with the resolution of 0.5m or less. The system has proven to be fully operable, will be used more frequently and will be able to expand its application area if it meet with the local flight regulations.

Work in the field and Results
The City of Chonburi, the eastern coastal province of Thailand was selected to be the study area because there are many reasons such as its location of Ultralight plane company, CMT, its variety of land cover etc. With a contrast altitude and horizontal flight, almost images recorded by RDC-7 color camera is near vertical images excluding images during the plane take-off, landing, and turning. (See Figure) The image recorded above the city is very clear with 0.5-m ground resolution or less. (See Figure 4) Each image has 640-pixel by 480-pixel size in form of jpeg.


Figure 4 the images of Chonburi city

Unfortunately, the system testing time is in August, the rainy season period although the day for the system experiment is clear and opened sky, however, the thin haze is in sky during system test flight. Therefore the haze exists in some images. Those image with haze are record always above the vegetation area because that are is very humid specially on the system-test day (See Figure 5)


Figure 5 noised and non-noised images above the same area during the test flight

Conclusion
The new way to improve the weak point of the satellite image has been developed with a lower cost but more detailed image as well as time-selected record for the important mission such as the visualization and animation of cultural heritage. It is the sensor mounted with light plane. In the terms of the image processing for the visualization and animation, the image is sufficient qualified for the further processing with the standard resolution and size. Moreover, this observation is the starting point to design and develop the new, challenge, cheap field surveying from the sky such as the sensor integration (GPS and a digital CCD camera) mounted with balloon or the RF video on the light plane for field observation etc.

Recommendation and Further Research
This experiment can distribute the near-vertical images with the digital form but there are some problem to modify and research further:

  • Twin cameras should be applied to record the overlap images for easy 3d processing.
  • GPS should be integrated with the system to avoid the ground control point building in the fields.
  • The flight of the aerial photo should be restricted rigidly to obtain the near vertical images and a block of the digital aerial photo.
  • Due to distribute the qualified images, the system should be tested in the Cultural Heritage area such as Ayuttaya, the world heritage etc.
  • The images should be processed in the next step for a 3d visualization or 3d ancient-city model

Moreover, in AIT, STAR program by the students of Space Technology course attempt to develop the other new field observation. That method is the sensor, a CCD digital camera mounted with balloon platform. The expected result is suggested to show at the poster session in this conference. (See figure 6)


Figure 6 the digital CCD camera mounted on a balloon platform

Acknowledgement
Special thanks for CMT to distribute the Ultralight Plane for this experiment.

Reference

  • M. Kusanagi March 2000, “Remote Sensing, Geographic Information System and Global Positioning System Training Delivery System” RESAP Remote Sensing Specialist Meeting, UN- ESCAP, Bangkok.
  • M. Dufo Kusanagi, Oct. 1999, “Feasibility Study of Space Development Project for South-East Asian Countries; Mobile Multi-mission Compact Ground Systems” (in Japanese), Space Science and Technology Federation Meeting, Kobe.
  • Kaew Nualchawee, , Dec.1997, “Space Technology Applications and research: What’s in the STAR”, Asia-Pacific Conference on Multilateral Cooperation in Space Technology and Application, Univ. of Bahrain.
  • S. Murai, L. Samarakoon and K. Honda, Nov. 1998, “Activities of Education, Training and Research at Asian Institute of Technology” Asian Conference on Remote Sensing, Manila.