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Metadata
- Why We Do It
Portable
Metadata - kindness to end-user
Simple definition
of metadata:
"What
you need to know about data that you receive from someone else in order
to use it intelligently - or at least avoid making stupid mistakes"
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should be “attached”
to data
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platform-neutral
or “open”
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MassGIS data standard
as example
Enterprise
Metadata - Management Tool
Enterprise
metadata is what you create for yourself or for your colleagues specifically
for use in your organization
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Doesn’t have to
travel
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May be software/application
specific
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e.g. documentation
of procedures or symbolization
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May be part of
complex overall relational data management framework, inventory or global
metadata
Enterprise data can be complex
Portable metadata:
What do you need to know?
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What is this stuff?
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Name
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filenames, tiling,
file format
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a description
in plain English would be nice
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if on-line, keywords
to facilitate finding it
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representation
model
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point, polyline,
area, image, raster, network, CAD
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network chain
- planar graph
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GT polygon composed
of rings
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projection, units
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How good are the
data - lineage
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from what source
onto what basemap (if any)
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what is the appropriate
spatial accuracy metric
| Source |
Accuracy Metric |
| GPS |
absolute accuracy (conditions,
PDOP) |
| paper map or CAD |
accuracy as function of
scale & accuracy standard |
| personal knowledge |
how to quantify?? |
| address match |
hit rate, interpolation
error |
| satellite classification |
ground sampling rate, classification
error |
| photogrammetry |
photo scale, resolution
or minimum feature size |
| photointerpretation |
classification error |
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How good are the
data - do you trust them?
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by whom were they
automated
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interns, contractors,
in-house staff
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how were they
automated
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imported, scanned,
digitized on-screen, tablet
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how were they
processed
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converted, projected,
resampled, generalized, rubber-sheeted, snapped, degraded or otherwise
“edited”
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Bottom line:
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what’s the final
estimate of the accuracy?
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What are the attributes?
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name, datatype,
valid range, units
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database links
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For code values
in the attribute table:
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what does each
code mean!
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How good are the
attributes?
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how current are
they & how frequently updated
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what is their
estimated accuracy
Enterprise
metadata: using it fully
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If you can control
application development, you can really leverage metadata:
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make it accessible
to end-users
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control use of
data
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scale minimum
and maximum
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appropriate symbolization
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“themes” with
built-in queries
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MassGIS “theme
inventory table”
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listing of all
themes, sources and display parameters
Built-in metadata
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describe data
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In customized
MassGIS Viewer the “Describe” option under Theme menu brings up the text
description of the highlighted data layer - such as open space, land use,
or roads
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textual description
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A full-page description from the MassGIS Datalayer Guide is accessible
in the MassGIS Data Viewer, containing an overview and information on attributes
and production
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how data is presented
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Theme inventory table lists data source, menu labels, field to be symbolized,
lookup table for decoding values in that field and legend file to be used
for symbolization
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symbolization
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coded item values in attribute table
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Symbolization described by symbol option and color in legend
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Metadata supplies code lookup for legend labels
Enterprise
meta-data - objectives
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Make metadata
available to all users through application framework
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Build on individual
efforts by facilitating reuse of project-specific work - e.g. modular code,
comments
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Document not only
the data but also how they are queried, presented and used
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Provide tools
to make meta-data relatively painless & enforce metadata requirements
Contact Information:
Christian Jacqz
GIS Manager, MassGIS
Phone: (617) 727-5227 ext. 309
E-Mail: Christian.Jacqz@state.ma.us
MassGIS
Presentations Index
Last Updated 4/19/2000
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