Distinguishing vegetation communities

Aerial Photography for Land Cover Mapping and

Habitat Analysis

Understand the difference between land cover, vegetation, ecosystems, and habitat

Understand the general procedure used for mapping land cover using remote sensing

Understand the importance of scale and MMU.Be able to construct a classification scheme for

mapping.Understand the role of photointerpretation and

interpretation keys.Understand the importance of accuracy

assessment in mapping.

Learning Objectives

VegetationThe act or process of vegetatingAll of the plant life in a particular region (e.g., the

vegetation of Wyoming) or period (e.g., Pleistocene vegetation)

EcosystemAn 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

HabitatHabitat includes the physical requirements that a species

requires to live.

Some definitions…

Scope the projectAcquire the aerial photography (or satellite

data)Develop a classification scheme (mapping

legend)Explore the area on the ground (if possible)Develop an interpretation keyCreate land cover units (make the map) Assess the accuracy of the productRefine as necessary

Mapping land cover: General procedure

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?

Scoping the project

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

Minimum Mapping Units (MMU's)

Copper Mountain, Colorado (IKONOS image)

MMU determines which clearcuts get mapped

What qualities does the aerial photography need to have to accomplish the mapping task?Dates/timesSpatial scale/resolutionSpectral 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.

Acquiring aerial photography

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!

Land Cover Classification Schemes

How would you classify this produce?

• 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

Characteristics of classification schemes

I. VegetatedA. Forest

1. Evergreena. Spruce-fir forest

i. Spruce-fir with winterberry understory

b. Lodgepole pine forestc. etc.

2. Deciduous

B. Shrubland

II. Non-Vegetated

Example of a simple hierarchy

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 Dryopteris goldiana, Panax quinquefolius, or Impatians pallida....... Acer saccharum-Fraxinus americana-Tilia americana Forest Alliance 6b. Forest of mid-elevation slopes and ridgelines; Acer saccharum typically co-dominant with Betula alleghaniensis and/or Fagus grandifolia........................................................... Acer saccharum-Betula alleghaniensis-Tilia americana Forest Alliance 5a. Quercus rubra 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.

Example of a more complex scheme used in the "real world"

Critical for understanding the distribution of land cover in the real world

Helps you choose useful ancillary dataUseful for understanding aerial photos back

at the computerNice to get out once in a while

Exploring the ground (field recon)

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

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

Interpretation keys should include the following:Explicit written description of each type in the

classificationExamples of each type as it appears in the

aerial photography being usedA list of key features of the type that can be

used to distinguish it from other typesCan take the form of a dichotomous key like you

would use for keying out plants or animalsShould be organized into an easy-to-use

notebook or in some kind of digital format (e.g., hyperlinked web key)

Interpretation keys

Classification can take two basic forms:Manual photointerpretation of the imagery

On hard copy using clear overlays or other toolsOn computer screen by digitizing with mouse

Per-pixel classification of digital imageryNot 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

Photointerpretation/classification

Detailed view of Wyoming GAP Land Cover Map

Wetland community mapping – University of Wisconsin

Horticulture map at University of WisconsinIndividual shrubs delimited with carefully rectified orthophoto

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 moneyCan be quantified using a suite of accuracy

assessment metrics

Assessing accuracy

If product accuracy is not sufficient must refineAssess 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?

Product refinement

Habitat is usually a combination of land cover with other spatially distributed environmental driversClimateSoilsProximity to waterAvailability of coverContiguity of cover types needed for different

parts of the life cycleAvailability of food/preyEtc.

Typically combine these as spatial layers in a GIS

Using land cover data to create habitat maps

GIS Habitat model schematic for Wild Boar

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

Summary