(First draft, 14 March 2014. Updated 19 March 2014)
After spending 2 days on Tomnod, I think it is rather lack of refer for the participants to identify what they are looking at. I have been conducting ocean survey in South China Sea area, and I hope some of the identification below will be able to assist the Tomnod participants better.
Where is the area you are observing?
South China Sea and Gulf of Thailand. From Tomnod Tweet, possibly Malacca Straits is included. These are located in the tropical ocean. Very shallow sea (50-100m).
What you want to find?
Our task is to find the indicator that can lead to the discovery of MH370 Missing Airplane. The three main indicators preselected by Tomnod is Airplane Wreckage, Raft and Oil Slick. The participant can also make other interesting observation by category “Other”.
What you need to do after accessing Tomnod?
What you will see once you open “Start Tagging”?
I noticed Digital Globe provides two kind of satellite imageries, Panchromatic and RGB Composite Image. Panchromatic Image is the satellite image that come with only grey scale color, just like the black and white photo. RGB Composite image is the combination of the satellite band to make the satellite image looks like true color, or color photo in layman term. In some scene, you will find the combination of both Panchromatic and RGB Composite image. What I noticed is that Panchromatic Imagery has higher spatial compare to RGB Composite.
Browsing the High Resolution Satellite Imagery
Please don’t get shock when you found a totally blueish or grey screen even scrolling your mouse for a few more “tiles” (The full scene is divided into block of smaller image called tiles). As some part of the clam ocean will appear homogeneous until you encounter the cloud or some other features that will make it feel more interesting to browse.
Browsing the Tomnod satellite imagery just similar to the Search and Rescue mission on the air and ocean. We need to plan, not simply drag the cursor anywhere to look for MH370. The adjacent image tiles will be related to your current image tiles, as the result, you need to follow some pattern similar to conducting surveying in the ocean. In many cases, the satellite image might not be in rectangular shape after the georeference process, it is not an error.
When you reach the edge of the Tomnod scene, you will notice the black color frame. You can ignore the image tiles located at the Scene’s black frame region as there is No Data. If the image tile consists both satellite imagery area and black frame, I will recommend you to take a look.
Border of Satellite Imagery – In some image (Yellow Box below), you will find the color difference between two satellite images. It could possibly occur due to the different atmospheric correction and image enhancement applied on these imagery before they are combined into one single image. Some of the imagery border can be in very high contrast like example below.
Big contrast between the border of two RGB composite images
Border of four images. The scene is combination of various images. Due to the factor where each images are process differently before the combination, there is large contrast when you browse from one image to another. Please don’t get confuse, it is not an error.
What can I found in the Tomnod satellite imagery?
You will find a large portion of the satellite imagery is the ocean, either in grey blue for RGB composite image, or grey color in the panchromatic image.
Cloud’s Shadow – if you encounter an area in the ocean with darker color, you need to check for adjacent area if there is a cloud. The dark color area could be cloud’s shadow.
Whitecaps – the white color bubble from the ocean wave.
Ship/ Vessel – South China Sea, Gulf of Thailand and Malacca Straits are busy sea lane. There are many fishing activities conducted in these area. Currently, there are more than 40 ships are conducting Search and Rescue operation in these area.
Oil Slick – floating linear type of features on the ocean surface can be easily identify using RGB composite image. In some area, there is a phenomena called “phytoplankton bloom”, where there is dense concentration of phytoplankton that make it visible in the satellite image. Their distribution pattern is very much similar to oil slick. We can differentiate them using multispectral images. I noticed that the oil slick is rather difficult to be identified in the Panchromatic imagery.
Oil and Gas Platform – these areas are producing petroleum and natural gas
Ocean Front – In the coast region, the coastal water can be easily differentiate from the blue oceanic water. The edge of the coastal water is call ocean front
Boay – boay are stationary in the ocean. Some of the boay are big enough to be detected by the high resolution imagery.
What will happen after we select and tag the object?
There will be a color circle appeared and surrounding the tagged object. You can also remove the tag by mouse over the purple circle, there will be a “deleting cross” appear, just click on the cross to remove the tag.
What if you found an Airplane in Tomnod?
I believe you will be excited, but it might not be the MH370 missing plane that we are looking for. It is possible for space satellite to capture flying airplane in the ocean or over the land. As the Tomnod participants don’t have the detail information about the location that we are looking at (the coordinate), it is rather difficult for us to determine whether the air plane in the imagery is MH370 wreckage or just the coincident a passing by air plane.
As a responsible user, we need to tag the air plane, and leave it for Tomnod to verify if it is MH370. Please do not spread the news of the found air plane around before the verification is “correctly” done. We need to leave the announcement to be conducted by the authority. Any false information release will create extra workload for the SAR mission and more importantly causing secondary damage to the victim’s family.