Aerial Photography for Land Cover Mapping and Habitat Analysis

1. Aerial Photography for Land Cover Mapping and Habitat Analysis Distinguishing vegetation communities

3. Some definitions… • Vegetation • The act or process of vegetating • All of the plant life in a particular region (e.g., the vegetation of Wyoming) or period (e.g., Pleistocene vegetation) • Ecosystem • An interacting system of biotic (plants, animals, microorganisms) and abiotic factors (the environment) • Land Cover • All of the features occupying the land surface including vegetation, unvegetated areas, natural and human affected • Habitat • Habitat includes the physical requirements that a species requires to live.

4. Mapping land cover: General procedure • Scope the project • Acquire the aerial photography (or satellite data) • Develop a classification scheme (mapping legend) • Explore the area on the ground (if possible) • Develop an interpretation key • Create land cover units (make the map) • Assess the accuracy of the product • Refine as necessary

5. Scoping the project • What is the desired mapping scale? • What is the MMU? • What resources are available (data, money, etc.)? • How much time is available to do the project? • How accessible is the map area?

6. Minimum Mapping Units (MMU's) • The minimum mapping unit is the smallest area that will be digitized or classified on your map. • Very important decision because it determines what patch sizes will be subsumed and which will be retained • Will have different effects on map depending on the spatial configuration of the area (E.g., is the area composed of large homogeneous areas or is it patchy) • Sometimes maps have different MMUs for some types (e.g., riparian) than others • MMU is limited by resolution of the imagery

7. MMU determines which clearcuts get mapped Copper Mountain, Colorado (IKONOS image)

8. Acquiring aerial photography • What qualities does the aerial photography need to have to accomplish the mapping task? • Dates/times • Spatial scale/resolution • Spectral resolution (panchromatic, true color, false color IR, etc.) • Geometric properties (orthorectified, vertical, oblique, etc.) • Amount of overlap for stereo viewing, etc. • Are suitable photos available (e.g., NAPP) • Are contractors available to fly if no archive is suitable? • Costs, timing, etc.

9. Land Cover Classification Schemes • How many types do you want to map? • How should you divide up the features you are interested in? • What resources do you have? • How will your interpretation be used? • What do the funders want! • Can be very controversial!

10. How would you classify this produce?

11. Characteristics of classification schemes • Must be useful • Types must be detectable using the data you have • Should be hierarchical • Categories must be mutually exclusive • Require explicit definitions of each class

12. Example of a simple hierarchy • Vegetated • Forest • Evergreen • Spruce-fir forest i. Spruce-fir with winterberry understory • Lodgepole pine forest • etc. • Deciduous • Shrubland • Non-Vegetated

13. Example of a more complex scheme used in the "real world" 1a. Trees (woody plants usually over 5m tall) present and forming 10-100% cover. 2a. Trees with their crowns interlocking, forming 60-100% [FOREST].....................................................................3 3a. Deciduous species contribute >75% of the total tree cover Deciduous Forest 4a. Upland.............................................................................................................................5 5a. Acer saccharum dominant in the canopy................................................6 6a. Forest of sheltered hillsides or pockets (coves), with moist comparatively rich soils, sometimes bouldery; Acer saccharum usually strongly dominant; herb layer may contain rare species such as Dryopterisgoldiana, Panaxquinquefolius, or Impatianspallida....... Acer saccharum-Fraxinusamericana-Tiliaamericana Forest Alliance 6b. Forest of mid-elevation slopes and ridgelines; Acer saccharum typically co-dominant with Betulaalleghaniensis and/or Fagusgrandifolia........................................................... Acer saccharum-Betulaalleghaniensis-Tiliaamericana Forest Alliance 5a. Quercusrubra dominant in the canopy..............................................................................etc. 4b. Wetland..................................................................................................................etc. 3b. Deciduous species contribute <75% of the total tree cover.....................................................................etc. 2b. Trees forming open to very open strands, with crowns not usually touching........................................................etc. 1b. Trees absent, or less than 5m tall, or forming <10% cover...........................................................................................etc.

14. Exploring the ground (field recon) • Critical for understanding the distribution of land cover in the real world • Helps you choose useful ancillary data • Useful for understanding aerial photos back at the computer • Nice to get out once in a while

15. What characteristics of this landscape might be important for making a map using aerial photography?

16. How would you classify this vegetation and where are the boundaries??

17. Interpretation keys • Interpretation keys should include the following: • Explicit written description of each type in the classification • Examples of each type as it appears in the aerial photography being used • A list of key features of the type that can be used to distinguish it from other types • Can take the form of a dichotomous key like you would use for keying out plants or animals • Should be organized into an easy-to-use notebook or in some kind of digital format (e.g., hyperlinked web key)

19. Photointerpretation/classification • Classification can take two basic forms: • Manual photointerpretation of the imagery • On hard copy using clear overlays or other tools • On computer screen by digitizing with mouse • Per-pixel classification of digital imagery • Not used as commonly with aerial photography because the spectral resolution is not as good as in multispectral satellite imagery. • Will talk about this more in the context of satellite data

22. Detailed view of Wyoming GAP Land Cover Map

23. Wetland community mapping – University of Wisconsin

24. Horticulture map at University of Wisconsin Individual shrubs delimited with carefully rectified orthophoto

25. Assessing accuracy • Accuracy assessment is crucial for any mapping project • Requires extensive field work to compare what is on the ground to what is designated on the interpreted photo • Can be expensive – field work costs money • Can be quantified using a suite of accuracy assessment metrics

26. Product refinement • If product accuracy is not sufficient must refine • Assess the original data – are problems related to the information content of the data? • Assess the interpretive process – are problems related to inconsistent or poor photointerpretation? • Does the interpretive key need to be revised/amended? • Assess the classification scheme – is the list of types appropriate and mappable. • Would moving “up” the hierarchy be useful and if so would the map still be appropriate for users?

27. Using land cover data to create habitat maps • Habitat is usually a combination of land cover with other spatially distributed environmental drivers • Climate • Soils • Proximity to water • Availability of cover • Contiguity of cover types needed for different parts of the life cycle • Availability of food/prey • Etc. • Typically combine these as spatial layers in a GIS

29. GIS Habitat model schematic for Wild Boar

30. Summary • Land cover is the collection of features occupying the land surface • Air photos are useful for mapping land cover, especially at fine scales • Land cover mapping is a process with a series of important steps, each of which must be carefully executed • Our ability to accurately map land cover can be limited by the quality of the photography or other data that we are interpreting • Important to be realistic about what can be accomplished