Irregular Morphing for Real-Time Rendering of Large Terrain

The following paper proposes an alternative approach to the real-time adaptive triangulation problem. A new region-based multi-resolution approach for terrain rendering is described which improves on-the-fly the distribution of the density of triangles inside the tile after selecting appropriate Level-Of-Detail by an adaptive sampling. This proposed approach organizes the heightmap into a QuadTree of tiles that are processed independently. This technique combines the benefits of both Triangular Irregular Network approach and region-based multi-resolution approach by improving the distribution of the density of triangles inside the tile. Our technique morphs the initial regular grid of the tile to deformed grid in order to minimize approximation error. The proposed technique strives to combine large tile size and real-time processing while guaranteeing an upper bound on the screen space error. Thus, this approach adapts terrain rendering process to local surface characteristics and enables on-the-fly handling of large amount of terrain data. Morphing is based-on the multi-resolution wavelet analysis. The use of the D2WT multi-resolution analysis of the terrain height-map speeds up processing and permits to satisfy an interactive terrain rendering. Tests and experiments demonstrate that Haar B-Spline wavelet, well known for its properties of localization and its compact support, is suitable for fast and accurate redistribution. Such technique could be exploited in client-server architecture for supporting interactive high-quality remote visualization of very large terrain

TOWARDS ADAPTIVE HIGH-RESOLUTION IMAGES RETRIEVAL SCHEMES

Nowadays, content-based image-retrieval techniques constitute powerful tools for archiving and mining of large remote sensing image databases. High spatial resolution images are complex and differ widely in their content, even in the same category. All images are more or less textured and structured. During the last decade, different approaches for the retrieval of this type of images have been proposed. They differ mainly in the type of features extracted. As these features are supposed to efficiently represent the query image, they should be adapted to all kind of images contained in the database. However, if the image to recognize is somewhat or very structured, a shape feature will be somewhat or very effective. While if the image is composed of a single texture, a parameter reflecting the texture of the image will reveal more efficient. This yields to use adaptive schemes. For this purpose, we propose to investigate this idea to adapt the retrieval scheme to image nature. This is achieved by making some preliminary analysis so that indexing stage becomes supervised. First results obtained show that by this way, simple methods can give equal performances to those obtained using complex methods such as the ones based on the creation of bag of visual word using SIFT (Scale Invariant Feature Transform) descriptors and those based on multi scale features extraction using wavelets and steerable pyramids

Geomorphological and archaeological investigations in the Euphrate Plain in Syria: comparison between SAR and optical data (poster session)

The use of remote sensing in archaeological prospecting is rarely mentioned in the literature. Yet, in countries where cartographic coverage is antiquated or inaccurate and aerial photographs are unavailable, satellite images allows the generalisation of field observation. In this research, two issues are addressed: how can remote sensing improve the knowledge of the palaeogeography and what sort of images are most useful for archaeological prospecting. We have utilised two sensors' data: SPOT radiometer (HRV) and ERS1 AMI SAR. The study was designed to measure remote sensing supplies in dissimilar contexts : textural image processing (co-occurrence matrix), G.I.S. method (superposition), geomorphologic cartography (ancient river meandering, ancient terraces, natural levees,caves), dynamic geomorphology (actual river meandering) and archaeological prospecting. Some field recognised features have been mapped. For instance, in relation with soil texture and surface roughness, an ancient irrigation or ship canal of Early Bronze Age is visible on SAR and SPOT images. Moreover correlation between ancient natural levees and present irrigation network and river crosscutting in Jebel Tell Masaïkh (Ozer, 1996) are also observable. The superposition in a G.I.S. with thematic maps supplies us with a complement of information's (length of ancient canal) which gives us the possibility to predict flows. The present study demonstrates the great value of " visible " images in comparison with SAR data. These one would produce more interesting information's combining multitemporal images, multifrequency images and variable incidence angle