Lineage

Review of standard:
"a description of the source material from which the data were derived and the methods of derivation, including all transformations invovled in producing the final digital files"

It's about time.

Record what you know, when you know it.

Trace the history of operations and transformations.

Extremes of handling lineage

Sheet-based compilation:

• All geometry comes from one image (or block of images), subject to control to tie it down.
• Episodic update (often complete replacement)
• Snapshot coverages, time much more fixed (photo interp, remote sensing)
  Examples: Dane County Soil Survey, USGS topo quads, NOS hydro surveys ...

Object-based maintenance:

• each feature placed on its own distinct source
• requires individual coding (as on Chart History - see example in Report 4)
  Examples: Nautical chart, some parcel maps

Most data sources involve mixtures of both:
eg. nautical chart: shorelines and shore landmarks from photogrammetry (sheets) but aids to mariners from individual letters, etc. (see NOS report)

Dates tell a story

History of Topographic Mapping: priority mapping means that most improtant places get mapped first - a good thing at first. However when the series is complete, they get stuck with the oldest coverage.

Processing History

Lineage is not just sources materials, but also processing and manipulation.
Some software records steps (as Arc/INFO), but may not show what changed...
Only steps that change something need be recorded.
Control: registration to digitizer, registration to ground points
Projection: conversion from map to ground, and onto some other proj.
Change in resolution: integer roundoff, raster to vector and reverse...
Change in dimension: two line to single line, polygon to point, etc.

Horizon of lineage

Ideal lineage is cradle to grave
branching nature will lead to cumbersome and duplicative reports
References to lineage in each prior version (linked list backward)
automated transaction logs implemented in some systems
Do they record the right things?

Agencies are responsible for what they did, not some later owner of the data.
(some agencies like USGS shed their records...)

Version of 14 January 2004