Activiities of ASTER Working Groups OMP L1/ DEM Calibration Atmospher TES HLDP Geology Eco/Ocean ASTM Info.	Tokai Univ. Kiyonari Fukue ASTER Ortho Products are ortho images, and this is the name covering ASTER level 3 products that have features that can be layered on a geographical map. Currently, three kinds of ortho products, level 3A, 3B and 3C, are scheduled to be produced. The L3A product is just called an ortho product, and the L3B and L3C products are called GCP, using ortho products and mosaic/multi-period ortho products respectively. Here, the L3A ortho product, which may have the largest demand, is briefly introduced. When we observe the surface of the land from a single point such as a satellite in order to observe it, each point of the land is observed with geometric distortion as shown in Figure 1 (a), depending on the land topography. In order to correct the geometric distortion caused by the land topography, the land surface should be vertically projected on a projected plane as shown in Figure 1 (b). The former is called a center graphic projection and the latter is called an orthographic projection. An image that has no topographical distortion is generally called an ortho image. One example is an image produced by orthographic projection. Fig.1 Center projection and Orthographic projection L3A is a product that consists of data that was radiometrically calibrated and geometrically coregistered as L1B. In addition, it has the following features; [1] no local distortion is produced, [2] the map projection method can be selected from a menu, [3] SWIR high accuracy parallax correction can be performed, [4] rearrangement (resampling) is prepared with a single rearrangement (resampling) from sampled raw data, [5] the calculation load to produce images is low and the image can be produced quickly, and [6] a DEM (Digital Elevation Model) that can be layered onto the ortho image is attached. No explanation is necessary for [1]. Concerning [2], each mapping method such as UTM, LCC, Mecator or Polar-stereo projection uses longitude and latitude. This is also applied to a local measurement point coordinate such as a map of Japan with the earth ellipse model. Concerning [3], one or two misregistrations of pixels in the SWIR bands have occurred due to parallax as a result of the different image locations of the CCD arrangement in SWIR as one of the subsystems of ASTER. However, we are aiming correction treatment with a high accuracy compared to the case of Level1B. Concerning [4], it is done to allow users to easily carry out calculations based on the radiation brightness, minimizing changes in observations due to repeated rearrangements. Concerning [5], it is necessary to distribute the KL3A product to many users using limited facilities on the ground. This is the most difficult feature for the Level 1/ geometry correction working group that has been studying the algorithm for Level3 product, which is somewhat different from the one generally used. Concerning [6], this is necessary for users, because it makes it possible to check the correction accuracy of topographical distortion., It also becomes possible by utilizing DEM to generate stereo images having a BH ratio or with various high-order calculations using tilt angle or altitude. ASTER has three subsystems, the previously described SWIR, and VNIR and TIR in addition. VNIR has the officially announced ground resolution of 15m/pixel, and consists of two telescopes, one for nadir viewing and one for backward viewing. Figure 2 shows simulation images viewed by those telescopes. The location is Mt. Fuji and the surrounding area. Figure 3shows the ortho image produced by L3A processing and with the DEM attached. ASTER Ortho Products aims at operability of data utilization from a geometric aspect. We expect that the Ortho Products will be valuable for users and will be widely utilized. Figure2 : VNIR simuration images (a) Nadir view (b) Backward view Figure 3 : VNIR Ortho Products [Map projection: UTM] (a) Ortho image (b) DEM (Shown with shadows) ( Level 1/Geometric/DEM WG )