Transect Sherd Density

Aggregate strip-collected sherd density with caller detection probabilities, using physical exposure areas rather than averaging unequal transects; detection correction is a model, not total site inventory.

Description

Sherd density from strip collection depends on the area actually searched and the chance of detecting material.

Sherd density from strip collection depends on the area actually searched and the chance of detecting material. Correcting counts before pooling avoids giving unequal transects equal weight.^[1]

When to use Transect Sherd Density

Use this tool to aggregate strip-collected sherd density with caller detection probabilities, using physical exposure areas rather than averaging unequal transects; detection correction is a model, not total site inventory.

Prepare the artifact, site or survey measurements and any independently established calibration or model choices. Keep paired observations aligned and confirm units and coordinate conventions.

How to use Transect Sherd Density and understand its results

Prepare the artifact, site or survey measurements and any independently established calibration or model choices. Keep paired observations aligned and confirm units and coordinate conventions.
Enter transectLengthsM, effectiveCollectionWidthsM, sherdCounts, detectionProbabilities using the field table and calculation rules, then run the tool.
Read observedSherdsPerM2, detectionAdjustedPooledSherdsPerM2. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
transectLengthsM	Transect lengths m	list of number	Required
effectiveCollectionWidthsM	Effective collection widths m	list of number	Required
sherdCounts	Sherd counts	list of number	Required
detectionProbabilities	Detection probabilities	list of number	Required

Pair positive transect lengths and effective widths in m, nonnegative integer sherd counts and detection probabilities greater than zero and at most one. Return raw density for each transect and the detection-adjusted pooled density in sherds/m².

Paired lists must be nonempty and have equal lengths.

area_i = length_i × width_i; observedDensity_i = count_i/area_i; adjusted pooled density = Σ(count_i/detection_i)/Σarea_i

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
observedSherdsPerM2	Observed sherds per m2	list of number
detectionAdjustedPooledSherdsPerM2	Detection adjusted pooled sherds per m2	number

json

{
  "input": {
    "transectLengthsM": [
      10,
      20
    ],
    "effectiveCollectionWidthsM": [
      2,
      1
    ],
    "sherdCounts": [
      10,
      30
    ],
    "detectionProbabilities": [
      0.5,
      1
    ]
  },
  "output": {
    "observedSherdsPerM2": [
      0.5,
      1.5
    ],
    "detectionAdjustedPooledSherdsPerM2": 1.25
  }
}

Limitations and assumptions

Detection probabilities and effective widths are supplied model inputs. The estimate is not a census of an entire site, and representativeness and detection uncertainty are not tested.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Numeric lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Surface Collection Sample Fraction: Compute area inclusion fractions and stratified expansion from sampled counts, assuming representative selection within each stratum; unequal strata are not replaced by a single uniform inclusion rate. For a complementary task, use NISP Specimen Count By Taxa Tool: Tabulate one taxon assignment per observed specimen while retaining explicitly unassigned records; fragmentation and element counts do not convert NISP to individuals.

References

Transect Sherd Density — tool.io

Similar or alternative tools

Surface Collection Sample Fraction
Compute area inclusion fractions and stratified expansion from sampled counts, assuming representative selection within each stratum; unequal strata are not replaced by a single uniform inclusion rate.
NISP Specimen Count By Taxa Tool
Tabulate one taxon assignment per observed specimen while retaining explicitly unassigned records; fragmentation and element counts do not convert NISP to individuals.