1. Supplemental Slide Set for GeoWorld Beyond Mapping Column, August 2004
See select Topic 22
The Hugag is a curious mythical beast with strong preferences for terrain configuration:
Prefers low elevations (severe nose bleeds at higher altitudes)
Prefers gentle slopes (fear of falling over and unable to get up)
Prefers southerly aspects (a place in the sun)
This slide set supports discussion on Suitability Modeling in the Beyond Mapping column for GeoWorld. The slides describe several techniques for determining the relative suitability of an area for an intended use– Hugag habitat in this case.

2. Hugags like… Gentle Slopes Southerly Aspects Lower Elevations
…how would you map Hugag habitat?
Hugags like…
Gentle Slopes
(under 30%)
Southerly Aspects
(E-W orientation)
Lower Elevations
(under 1800 feet)
Manual suitability analysis requires annotating requirements on a traditional paper map. The following three slides show such an attempt.
1500ft

3. Hugags like… Too Steep Gentle Slopes Southerly Aspects
Manual Drafting
Too Steep
Hugags like…
Gentle Slopes
(under 30%)
Southerly Aspects
(E-W orientation)
Lower Elevations
(under 1800 feet)
The areas that are too steep (over 30%) are delineated by identifying very narrow contour line spacing. The spacing is determined by relating the change in horizontal distance (scale bar) to the change in elevation (difference in contour interval).
1500ft

4. Hugags like… Not southerly Gentle Slopes Southerly Aspects
Manual Drafting
Not southerly
Hugags like…
Gentle Slopes
(under 30%)
Southerly Aspects
(E-W orientation)
Lower Elevations
(under 1800 feet)
The “northerly” areas (NW, N, NE and flat) are identified by the orientation of the contour lines.
1500ft

5. Hugags like… Gentle Slopes Southerly Aspects Lower Elevations Too High
Manual Drafting
Hugags like…
Gentle Slopes
(under 30%)
Southerly Aspects
(E-W orientation)
Lower Elevations
(under 1800 feet)
Too High
The “Too High” areas are identified as all areas above a specified contour line.
1500ft

6. Hugags like… Not Southerly Too Steep Gentle Slopes Southerly Aspects
Manual Drafting – McHarg Overlay
Not Southerly
Too High
Too Steep
Manual
Map Overlay
Hugags like…
Gentle Slopes
(under 30%)
Southerly Aspects
(E-W orientation)
Lower Elevations
(under 1800 feet)
All three maps of unsuitable areas are superimposed and the “clear” areas are determined to be good habitat as none of the unacceptable considerations occur within these areas.
1500ft

7. Hugags like… Too Steep = 0 Gentle Slopes Southerly Aspects
Computer Solution
Too Steep
= 0
Hugags like…
Gentle Slopes
(under 30%)
Southerly Aspects
(E-W orientation)
Lower Elevations
(under 1800 feet)
= 1
A computer map of the unacceptably steep areas are identified by first calculating a slope map for the area (slopes from 0 to 65%) then assigning the areas with slopes greater than 30% the value “0” (bad) and areas of less than 30% the value “1” (good).
1500ft

8. Hugags like… Not southerly = 0 Gentle Slopes Southerly Aspects
Computer Solution
Not southerly
= 0
Hugags like…
Gentle Slopes
(under 30%)
Southerly Aspects
(E-W orientation)
Lower Elevations
(under 1800 feet)
= 1
= 1
In a similar manner, an aspect map is generated then calibrated by assigning “0” (bad) to northerly and flat areas and “1” (good) to the suitable areas.
1500ft

9. Hugags like… Gentle Slopes Too High = 0 Southerly Aspects
Computer Solution
Hugags like…
Gentle Slopes
(under 30%)
Southerly Aspects
(E-W orientation)
Lower Elevations
(under 1800 feet)
Too High
= 0
= 1
= 1
= 1
A value of “0” (bad) is assigned to the areas above 1800 feet and a value of “1” (good) is assigned to the lower elevations.
1500ft

10. Hugags like… Gentle Slopes Southerly Aspects Lower Elevations
Binary Overlay
Hugags like…
Gentle Slopes
(under 30%)
Southerly Aspects
(E-W orientation)
Lower Elevations
(under 1800 feet)
= 1
= 1
= 1
The three individual suitability maps are multiplied together to identify overall suitability; 1*1*1= 1 indicates areas that are suitable considering all three preference maps.
1500ft
Times
1 * 1 * 1 = 1

11. Hugags like… Gentle Slopes Southerly Aspects Lower Elevations
Ranking Overlay
Hugags like…
Gentle Slopes
(under 30%)
Southerly Aspects
(E-W orientation)
Lower Elevations
(under 1800 feet)
= 1
= 1
= 1
If all three maps are added a count of acceptable conditions is generated– 1+1+1= 3 is the best and 0+0+0= 0 the worst. The result is more information on habitat suitability (ranking map) than simply implementing an automated version of the manual McHargian process (binary map).
1500ft
Plus
= 3

12. = 1 = 2 = 4 Gentle Slopes Southerly Aspects Lower Elevations
Binary-Progression Overlay
Gentle Slopes
(under 30%)
Southerly Aspects
(E-W orientation)
Lower Elevations
(under 1800 feet)
= 1
= 4
= 2
Substituting a binary progression of values for unacceptable areas (1= too steep, 2=too northerly, and 4= too high) and adding results in a unique value for each combination. This map contains more information than either the ranking or binary solutions. 1 2 4
1500ft
Plus
= 7

13. Rating Overlay (Goodness Scale 1 to 9)
Hugags like…
(on a scale of 1 worst to 9 best)
Gentle
Slopes
= 5.0 (22%)
Southerly
Exposed
= 6.0 (West)
A rating suitability map uses a gradient of “goodness” instead of a simple bad/good binary appraisal. The conditions on each criteria map are “graded” on their relative habitat suitability (1= bad through 9= good) and the “ratings” are averaged for an overall score at each location. Dark green indicate the best conditions (8 to 9) while dark red indicates the worst (1 to 2).
1500ft
Lower
Elevation
= 5.0 (1,300)
Average
= 5.3

14. Hugags like… Constraints Overlay Good 9 Bad 1 Lake 0 Habitat Rating
OK= 4.5
Lake 0
Hugags like…
Habitat
Rating
Bad= 1 to
Good= 9
Covertype
A binary map of areas that are impossible habitat (open water as hugags can’t swim) are identified as “0” is used to update the rating map.
Water
Mask
Water= 0
Land= 1
Lakes
1500ft
Water = 0 times
any Habitat Rating = 0

15. Suitability draped over
Hugags like… Gentle Slopes, Southerly Aspects, Lower Elevations
Applying the Average Suitability model to a larger area shows its strong relationship to terrain configuration. Note that the areas of best habitat (dark green) occur on the fairly gentle slopes that are southerly oriented and at lower elevations. Note that the worst areas (bright red) occur on steep, northerly slopes at higher elevations.
Best Habitat
Best Habitat
Applying the basis model to other areas simply requires input maps of elevation and water. The model was modified in this instance to make areas of “no aspect (flat)” acceptably oriented and flowing water (streams and rivers) as impossible habitat.
(West)
(South)
Suitability draped over
3D plot of Elevation