Description: This extension provides you with tools to generate a variety of surface characteristics of a landscape, using both projected and unprojected (i.e. latitude / longitude) digital elevation model (DEM) rasters. These tools include:
- Surface Area and Ratio of a landscape
- Slope, with 3 slope algorithm options
- Aspect, with 3 aspect algorithm options, and an additional tool to apply a traditional directional Aspect symbology to an existing Aspect raster.
- Hillshade, with optional hypsometric tinting
- Multi-directional Oblique-Weighted Hillshade, with optional hypsometric tinting
- Seven types of Landscape Curvature
ArcGIS has many useful tools for calculating slope, aspect, hillshade and curvature from DEM rasters. This extension offers some advantages over these existing tools in that:
- These tools correctly handle Latitude / Longitude Data: The existing ArcGIS tools typically do not work well with data in a geographic coordinate system (i.e. Latitude / Longitude coordinates). They expect the vertical units of a digital elevation model to be the same as the horizontal units, and at best they only allow you to enter in an adjustment factor (generally called a "Z-factor") to adjust your Z-units to your X/Y-units. This Z-factor adjustment method is cumbersome to implement with latitude/longitude coordinate systems because the correct Z-factor is both hard to calculate and changes with latitude. Geographic data is especially confounding because the X-units are not the same as the Y-units. Both are in "degrees", but a degree in latitude (Y-units) is not the same distance as a degree in longitude (X-units). Unfortunately, most free elevation data available online is only available in latitude/longitude coordinates. This data can be projected, but projecting raster data introduces errors in resolution and precision (see horizontal and vertical artifacts on illustration in manual). This extension modifies the algorithms used to calculate common morphological characteristics of the landscape so that they accurately work with latitude/longitude data without projecting the data or using Z-factor adjustments. All methods are described in detail in the manual, but in general this extension will always automatically detect the coordinate system of the raster and use the method appropriate for that coordinate system
- These tools offer several options not available in the standard ArcGIS tools: Including multiple slope and aspect algorithms, optional hypsometric shading for hillshades, the MDOW model for hillshades, and many more options for landscape curvature.
- Surface Area and Ratio: This extension allows you to generate Surface Area and Surface Ratio rasters from an existing Elevation raster. The cell values for these new rasters reflect the surface area and (surface area) / (planimetric area) ratio for the land area contained within that cell's boundaries. Both Surface Area and Surface Ratio provide useful indices of topographic roughness and convolutedness, and can give a more realistic estimate of the land area available than you can get from the simple planimetric area.
- These tools do not require Spatial Analyst: This extension uses only standard ArcGIS ArcObjects functions and therefore does not require a license for either Spatial Analyst or 3D Analyst.
Requires: ArcGIS 9.2 or better, at any license level, or ArcGIS 10.
Important: This extension does not require Spatial Analyst or 3D Analyst. It will work just fine without any add-on extensions
Thanks to Jeff Jenness
Thanks to Jeff Jenness
To download the extension :
