Collateral Material for Image Interpretation: Field Verification & Interpretation Keys (Especially for GATE-Geospatial 2022)

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Using Collateral Material

A review of all existing source material that pertains to a given area, process, type of facility or object, can aid in the interpretation process. The use of collateral material may also result in a better definition of the scope, objectives and problems associated with a given project. Also called “ancillary data” , the collateral material may come in the form of text, tables, maps, graphs, or image metadata. Census data, a map or description of the flora of a given area, a land use map, meteorological statistics, or agricultural crop report can all be used in support of a given interpretation. Basically, collateral material represents data/information that an interpreter may use to aid in the interpretation process. Material contained within a Geographic Information System (GIS) that is used to assist an interpreter in an analysis task can be considered collateral data. Two classes of collateral materials deserve special mention: interpretation keys and field verification.

Field Verification

Field verification can be considered a form of collateral material because it is typically conducted to assist in the analysis process. Essentially, this is the process of familiarizing the interpreter with the area or type of feature. This type of verification is done prior to the interpretation to develop a visual “signature” of how the feature (s) of interest appear on the ground. After an interpretation is made field verification can be conducted to verify accuracy. Fieldwork is sometimes calculated as being three times as expensive as lab analysis. (This is why good interpreters can be so valuable) . The nature, amount, timing, method of acquisition, and data integration procedures should be carefully thought out. Will you use windshield surveys, point or transect sampling? -Will the sampling be random or systematic?

GIS

Amount and Type of Field Work Required

The amount and type of field work required for a given project may vary greatly and is generally dependent upon the,

  • Type of analysis involved.
  • Image quality, including scale resolution and information to be interpreted.
  • Accuracy requirements for both classification, and boundary delineation.
  • Experience of the interpreter and the knowledge of the sensor, area, and subject.
  • Terrain conditions and the accessibility of the study area.
  • Personnel availability, access to ancillary material.
  • Cost considerations.

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