{"id":120221,"date":"2008-05-23T00:30:00","date_gmt":"2008-05-23T00:30:00","guid":{"rendered":"http:\/\/www.esri.com\/arcgis-blog\/products\/product\/uncategorized\/aspect-slope-map\/"},"modified":"2008-05-23T00:30:00","modified_gmt":"2008-05-23T00:30:00","slug":"aspect-slope-map","status":"publish","type":"blog","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/product\/mapping\/aspect-slope-map","title":{"rendered":"Aspect-slope map"},"author":4331,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"open","ping_status":"closed","template":"","format":"standard","meta":{"_acf_changed":false,"_searchwp_excluded":""},"categories":[22941],"tags":[38211,23201],"industry":[],"product":[],"class_list":["post-120221","blog","type-blog","status-publish","format-standard","hentry","category-mapping","tag-arcgis-methods","tag-cartographic-design"],"acf":{"short_description":"By Aileen Buckley, Mapping Center Lead\n\n\n\nAn aspect-slope map simultaneously shows the aspect (direction) and degree (steepness) of slope...","flexible_content":[{"acf_fc_layout":"content","content":"

By Aileen Buckley, Mapping Center Lead<\/strong><\/p>\n

\"Aspect-Slope<\/p>\n

An aspect-slope map simultaneously shows the aspect (direction) and degree (steepness) of slope for a terrain (or other continuous surface). Aspect categories are symbolized using hues (e.g., red, orange, yellow, etc.) and degree of slope classes are mapped with saturation (or brilliance of color) so that the steeper slopes are brighter. This will result in a map that has the colors shown to the right.<\/p>\n

NOTE — This blog entry has been updated for ArcGIS 10.<\/em><\/p>\n

<\/p>\n

The coloring is based on Moellering and Kimerling’s MKS-ASPECT scheme (GIS world 1991). Below is the aspect-slope map for the area around Crater Lake, Oregon.<\/p>\n

\"Aspect-Slope<\/p>\n

Cindy Brewer<\/a> and Ken Marlow describe the process for making this kind of map using ArcInfo GRID in their online article, Color Representation of Aspect and<\/em> Slope Simultaneously<\/a>.\u00a0 Translating the instructions to ArcGIS 3D Analyst<\/a> or Spatial Analyst<\/a> is straightforward. To try this yourself, download this dataset<\/a>. Included with the data is an .mxd file. Click here<\/a>\u00a0to download the style used to make the map above. These are the same colors Cindy and Ken originally used.<\/p>\n

Here is how to achieve this effect yourself:<\/p>\n

    \n
  1. First download the data and open the associated .mxd.<\/li>\n
  2. Using Style Manager, reference the aspect-slope style. To make things easier, you can also “un-reference” the Esri style. If you have a lot of content in your personal style, you will have to wade through this when you want to use the aspect-slope style as there is no way to “un-reference” your personal style.<\/li>\n
  3. Create a slope map from the Crater Lake DEM using the Slope tool<\/a> (this is in ArcToolbox under Spatial Analyst Tools -> Surface).\u00a0 Use the PERCENTRISE option for the Output measurement.<\/li>\n
  4. Create an aspect map from the Crater Lake DEM using the Aspect tool <\/a> (also in ArcToolbox under Spatial Analyst Tools -> Surface).<\/li>\n
  5. Reclass the slope map using the Reclassify tool<\/a> (also in ArcToolbox under Spatial Analyst Tools but this time, not surprisingly, in the Reclass toolset). Use these categories:
    \n0-5 : 10
    \n5-20 : 20
    \n20-40 : 30
    \n40-highest value : 40<\/li>\n
  6. Reclass the aspect map using the Reclassify tool<\/a>. Use these categories:
    \n0-22.5 : 1
    \n22.5-67.5 : 2
    \n67.5-112.5 : 3
    \n112.5-157.5 : 4
    \n157.5-202.5 : 5
    \n202.5-247.5 : 6
    \n247.5-292.5 : 7
    \n292.5-337.5 : 8
    \n337.5-359.5 : 1<\/li>\n
  7. Combine the two reclassed grids into an aspect-slope grid using\u00a0the Plus tool<\/a> (this is in ArcToolbox under Spatial Analyst Tools in the Math toolset). The input rasters are the slope-reclass grid and the aspect_reclass grid. Call it “aspect-slope”. This will create a new output grid with values in the 20s for low slope areas, 30’s for medium slope areas and 40s for high slope areas.\u00a0 The numbers will range from 21-28, 31-38 and 41-48 where the last digit relates to the aspect orientation (with 1 being north, 2 northeast, 3 east, and so on).\u00a0 Numbers less than 20 are essentially flat areas and will be assigned a gray color.<\/li>\n
  8. Now classify the results so that you can assign the appropriate colors:\n