Download Hill Shading and DEM Resolution: Techniques and Applications and more Slides Water and Wastewater Engineering in PDF only on Docsity! Resolution / Resampling Changing the resolution • Upscaling – if cells evenly divisible, use AGGREGATE • If not evenly divisible or changing the alignment, then use RESAMPLE • You can downscale, but this does not create any new information AGGREGATE Increasing the cell size by aggregating groups of cells into larger cells Based on statistical summary sum, min, max, mean, median RESAMPLE Interpolation methods Nearest Neighbor Fast, maintains original values, primarily for categorical data Bilinear or Cubic Fits data based on distance weighted functions, less geometric distortion, primarily for continuous data LiDAR Derived DEM / Raster Display… Hill Shading… Docsity.com 127 Hillshade DOQ 128 Hillshade DOQ ‐ study areas 129 Hillshaded DEM ‐Obliquely simulated illumination. 130 DEM display – Elevation Grid with “Standard” color ramp draped on Hillshade 131 Hillshaded Grid The Basics of Hill Shading… Docsity.com 1. Rendering the DEM with Data Frame Illumination ArcMap and its associated Extensions compute hillshade values for raster surfaces by considering the illumination angle and shadows. Hill Shading Method #2… 2. Image Analysis Window Supports the analysis and exploitation of image and raster data. Allows you to interactively adjust • Brightness ( ) • Contrast ( ) • Gamma ( ) • Transparently ( ) Enhancements are applied to the rendered screen display, not to the original raster dataset values. 147 Hill Shading Method #3… 3. Using Spatial Analyst & 3D Analyst to Create the Hillshade. 149 Rendering the DEM with Layer Properties Different stretches will produce different results in the raster display. A stretch increases the visual contrast of the raster display. You can experiment to find the best stretch for a particular raster dataset. 150 Docsity.com Rendering the DEM with Layer Properties Gamma The degree of contrast between the midlevel gray values. Low gamma coefficient darkens the middle tones. High gamma coefficient lightens the DEM. If the gamma coefficient is set too high, middle tones appear too light, can look bleached out. Does not affect the black or white values in a raster dataset, only the middle values. Gamma controls the overall brightness of a raster dataset. 151 152 Hillshaded DEM Problems with Hillshading… Problems with Raster Hill Shading Highlights features at right angles to the hypothetical light source. Landscape features can be lost in the Cast Shadows. Bottoms of low relief features such as ditches can be distorted. Visual interpretation of the distortion can lead to vertex coordinate shift from actual feature delineation and digitization. 154 Ground/Topography Displaying Slope with Hillshading… 156 Slope Docsity.com 157 Slope on Hillshade Drape the Hillshade on a DOQ… 159 Hillshade raster draped on DOQ exhibits the uniqueness of each product. DEM / Raster Display – Hydrography Identification… Problems with Raster Hill Shading An exploration of techniques to exploit hydrography. Visual Derived outputs Color symbology 161 162 Visually appealing symbology of LiDAR derived DEMs. Allows for effective visual interpretation of water conveyance features in regions of low topographic relief . Simple/Easy grid hillshade technique that adds visual complexity in place of obliquely simulated illumination. Hydrography Identification ‐A personal Mission ‐ Docsity.com