Trimble Navigation, Christchurch, New Zealand
Integrated Communication Systems, Colombo, Sri Lanka
National Technical University, Singapore
Trimble MediaMapper is desktop mapping software that links pictures, real-time video, and any other type of file to GIS map layers. It lets you create “interactive maps” that you can use in your GIS or on the Web. Interactive maps include layers for GPS tracks, waypoints, and locations of interest linked to multimedia files. By adding multimedia to our GIS we are able to:
- Add scanned documents like titles and plans
- Add historic imagery
- Document history by including audio and video interviews with local inhabitants
The spatial multimedia content generated can also be exported from the GIS and made available on the Internet. This rich source of material may assist in the reconstruction effort in northern Sri Lanka.
We chose to document two field sites using Trimble MediaMapper. The first was the A9 road that runs between Jaffna and Vavuniya, a major provincial town. We logged the centerline of the road so that we could update the previously digitized data. More importantly, by adding multimedia data, we are able to graphically represent the condition of the road, allowing any interested party to ascertain the current state. We also enhanced the documentation of the road with information about the condition of various towns and villages situated along it.
The second field site was the Muslim quarter in Jaffna, which has been extensively damaged by both LTTE and Sri Lankan troops. In the second field study area, our objective was to document the condition of the individual dwellings and the general condition of the amenities in the area. We took a digital photo of each dwelling and later added positional data so that we could build a database of dwellings.
Jaffna, the largest city in the north of Sri Lanka, is more than just a city for Sri Lanka’s Tamils: it is a symbol of statehood. Tamil leaders ruled the northern peninsula from Jaffna periodically from about the 11th century onwards, until the British took over in 1815. Although the Tamils lost control of the city, it has remained their cultural and political capital. In 1981 the Sinhalese police were accused of burning down an important library containing a collection of rare Tamil classics and manuscripts. Since then, animosity between the Tamils and Sinhalese has grown increasingly bitter. In 1987 a peace accord, overseen by Indian peacekeepers, gave control of the city to a new administration. In 1990, following India’s decision to withdraw its peacekeeping forces, the LTTE became the de facto administration. Upon taking control, the LTTE asked the Sinhalese and Muslims to leave. The Sinhalese accused the LTTE of “ethnically cleansing” the city. In 1996 the Sri Lankan Government recaptured Jaffna and imposed military rule. Successive strikes by LTTE forces captured the important town of Kilinochchi (1998) and the military base at Elephant Pass (2000), effectively cutting the supply route to Jaffna. The only access was by boat from the eastern port city of Trincomalee, or on flights arranged by the Sri Lankan Air Force. With LTTE forces closing in on Jaffna, the two parties signed a ceasefire agreement as part of a Norwegian initiative to end the civil war. Under the ceasefire agreement, the highway to Jaffna was opened for public traffic in April 2002.
Foreigners wanting to visit Jaffna need permission from the Ministry of Defense in Colombo. Fortunately the government agent in Vavuniya helped us to obtain the necessary permits in less than a day. We traveled about 10 kilometers north of Vavuniya to the Sri Lankan Army checkpoint, where a thorough search was conducted before we were allowed to cross into LTTE-held territory. Once in LTTE territory, we passed through a customs checkpoint, and were then allowed to travel freely until we reached the northern limit of LTTE territory. Again, we passed through LTTE customs and a Sri Lankan Army checkpoint, and then proceeded 30 kilometers to the town of Jaffna.
We collected data using a Trimble GeoExplorer 3 GPS receiver. Due to the sensitive nature of the area, we had to take care to openly display the GPS and digital camera equipment. While logging the A9 road from Vavuniya to Jaffna, the GPS receiver was kept in the vehicle’s glove box, with an external patch antenna magnetically attached to the roof. When we were walking the streets in Jaffna, the GPS receiver was in a pocket, with an external patch antenna running to a baseball cap on the head. The receiver logged GPS data automatically at 25-meter intervals while in the vehicle, and 5-second intervals while walking.
We used a Sony DSC-P3 digital camera to take still images, sound recordings, and short movies. These files were stored on a 128 MB Sony Memory Stick. When we returned to the office, the data was downloaded to a desktop computer running Trimble GPS Pathfinder Office, a GPS/GIS data processing package. The data was edited and then differentially corrected using base data from Integrated Communication Systems in Colombo, giving an accuracy of 2-5 meters horizontally. The corrected data then was exported to a GML (.gml) file. The GML file format is essentially a text file that lists Latitude, Longitude, Elevation, Date and Time in a columnar format, as seen in Figure 1.
Figure 1: GML file format The digital photos and movies were also downloaded to the desktop computer and placed in the same folder as the exported .gml file. The digital photos (in Joint Photographic Experts Group (JPEG) format) and the movies (in Moving Pictures Expert Group (MPEG) format) store date and time information in the header of the file, as seen in Figure 3. Trimble MediaMapper uses this information to match the multimedia files with GPS data.
Figure 3: JPEG file header
The next step was to use the Add Media wizard in Trimble MediaMapper. This wizard guides you, step by step, through the process of merging the multimedia files with the GPS track file. First we added names for the media layer (the layer that contains the digital imagery) and the track layer (the layer that contains GPS data). Then we specified the folders where the digital imagery and GPS data are located.
The final step was processing the data. The first part of the data processing is to calibrate the digital camera clock. This was done by taking a photo of the UTC time displayed by the GPS receiver, and then comparing it with the date and time displayed in the header information of the multimedia file. Trimble MediaMapper then calculates an offset, which is used to match each multimedia file with a position from the GPS track file. When data processing was complete, the data was displayed in the map window. We then added regional data from the Digital Chart of the World (DCW) dataset, and a geo-referenced scanned map of northern Sri Lanka to give some spatial reference to the collected data.
As we wanted to update the centerline data and view it in our GIS software, we exported the data to ESRI ArcGIS. Using the Trimble MediaMapper extension for ArcGIS, we could view the multimedia images in ArcGIS for a true picture of the road.
Figure 5: Viewing a digital image in GIS software
As the data collected had a far greater potential audience than those with access to ArcGIS, we wanted to convert the data into a more accessible format. We used the Export to HTML functionality of Trimble MediaMapper to create HTML pages. This allows us to display the information over the Internet or write it to a CD-ROM. A website is currently under construction.
This project allowed us to test the usefulness of a multimedia data collection system. Using a handheld GPS receiver and a consumer digital camera, we were able to collect still and moving imagery and add it to our GIS data. GPS data collection and image capture can be undertaken with less than one hour of training, making it possible for almost anybody to complete. This pilot project exceeded our expectations of being able to build a multimedia GIS database.
It has been said, “a picture is worth a thousand words”. One MPEG movie demonstrated to Norwegian mine clearing experts the extent of unexploded ordnance just 10 meters from the road . In another example, an image of part of the road showed non-governmental agency workers the difficulty of shipping goods by road.
Trimble MediaMapper has proven to be a versatile data collection tool that simplifies acquisition, organization, and extension of site-specific multimedia—digital photographs, audio, video, and digital documents. With Trimble MediaMapper we were able to automatically merge the source media with spatial information from GPS receivers, and build an interactive media map that is widely accessible via the Internet.