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Transect Methods

Transect Methods. Purpose of transects. Provide basic documentation Determine map unit composition Establish components and ROC. Directive. Policy and Procedures for Soil Surveys in Alaska Minimum map unit documentation Three transects per map unit Three complete pedons per component

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Transect Methods

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  1. Transect Methods

  2. Purpose of transects • Provide basic documentation • Determine map unit composition • Establish components and ROC

  3. Directive • Policy and Procedures for Soil Surveys in Alaska • Minimum map unit documentation • Three transects per map unit • Three complete pedons per component • Several complete pedons for each proposed series

  4. The Two Methods • The method to use is depending upon the distinctness and case of recognition of soil differences in the field • Line intercept method • Point intercept

  5. Line Intercept Method • Assumption-Components are discernable on the ground or by using photo interpretation or other remotely sensed technique • Layout • Direction is predetermined • Cross entire polygon from boundary to boundary • Observer recognizes each kind of soil as he/she passes its boundary • Reality-transects are located based on accessibility with multiple map units transected based on adjacency (study sites)

  6. An estimate of the relative extent of each component is made for the delineation • Direction is predetermined and the entire polygon • is crossed from boundary to boundary Other obvious minor components are included in the estimate even though they may not have been sampled A final estimate of composition is made for the delineation • Observer recognizes and samples each major soil at representative locations Line Intercept Example E A Map Unit A D B C Components A C %

  7. Point Intercept Example • Assumption-Components are not discernable on the ground or by using photo interpretation or other remotely sensed technique • Layout • Random direction • Cross entire polygon from boundary to boundary • Equidistant observations (usually 10-20) • Same number of steps are counted between stops • Composition is calculated • AK-Obvious minor components observed through photo interpretation are included in the composition estimates

  8. Point Intercept Example A A A A A B A A Component A-Bodenburg % 80 A A B-Yensus 10 C-Bodenburg, steep 8 D-Cryaquepts 2 Make 10 or more equidistant observations along the line, describe each stop and assign component Observe through photo interp any other components that may exist within the delineation Select a random direction across the entire polygon Make a final estimate of composition C D

  9. Summary • Line intercept methods is best method when components extent can be readily observed on the ground or remotely i.e. moderate to high relief terrain • Point intercept method is better when component-landscape or component-vegetation relations are not apparent i.e. low relief terrain • Regardless of method…composition estimates should include other obvious components not necessarily sampled during the transect

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