Near-lossless compression of Digital Terrain Elevation Data

In critical applications that are sensitive to information loss, lossless compression techniques are usually employed. The compression ratios obtained from lossless techniques are low. Hence we need different schemes that give quantitative guarantees about the type and amount of distortion incurred, viz. near-lossless compression methods. In this paper, we explore hybrid techniques for near-lossless image compression based on error bound per pixel and apply them to Digital Terrain Elevation Data (DTED). We develop multi-stage quantization methods and other hybrid schemes using SPIHT as an embedded lossy coder. The methods developed are scalable with a control on the maximum allowable deviation per pixel in the reconstructions. We compare the results obtained by these methods on the elevation images with JPEG-LS, the standard for lossless and near-lossless compression. Results show that these methods usually perform better than JPEG-LS in terms of compression performance and have additional features useful for progressive transmission.