North Carolina Geospatial Data Archiving Project

(NCGDAP)

Spatial Database

Image downloaded from USGSseamless data download

Archiving Migration andStandardization Strategies

XML DatabaseExport

TIFF Images

•Pixel Value and Header file•World file•Coordinate System file•Metadata file

Shapefiles

•Geometry file•Index file•Attribute file•Metadata file•Coordinate System file•Spatial Index files

Potential Archive Objects

Apex

Cary

Neuse

Garner

Raleigh

New Hope

Bethesda

Morrisville

tu70

tu1

tu401

tu64

tu401

tu70

tu1

tu401

tu64

§̈¦40

§̈¦440

§̈¦40

Raleigh-Durham International

William B Umstead State ParkWilliam B Umstead State Park

Carl Alwin Schenck Memorial FoCarl Alwin Schenck Memorial Fo

B. Everett Jordan Lake

Lake Wheeler

Falls Lake Reservoir

Lake Benson

Crabtree Creek

Neu s

e R

iver

Swift Creek

Swift Creek

N o r t h C a r o l i n a

How would you describeyour current geospatial

data archive?

How do you build an archive?

Last week’s set of nightly tape backups

Several boxes of CD’s and DVD’s

Bob’s hard drive

A collection of files in our “GIS Folder”

A stand-alone spatial database

The data back-end for our internet mapping application

An enterprise GIS

An archive must be… Achievement MethodsPersistent A defined plan for continuous data storage

Cataloging procedures and metadataFormat and media data migration, possibly also machine and software environment replication

Accessible nowAccessible in the future

Critical considerations for geospatial data

Common Risk Scenarios

Fragility of data storage media Bob’s hard drive could fail. Optical media deteriorates.

Proprietary format and data structure dependence

Formats become obsolete. Spatial data structures may be tied tosoftware and hardware environments that run their course.

Coincidence of business process data update and data archive cycles

Data is backed up and held for a limited period before being destroyed. Data is updated daily, but data “snapshots” are taken annually.

What will be in your geospatial data archive in 20 years?

The persistence – accessibility “Trade-off” for geospatial dataGeospatial data development and management involves unique “value-added” components that complicate the archiving of

geospatial data. The complex data structure of topology capture, spatial databases, and cartographic enhancements tobase data sets have provided special circumstances for those wishing to archive geospatial data. Providing access

to the data in its “original” state is an enormous challenge and will require significant compromise.

Archival Approach Issues and Opportunities

Vector-based approachesArchive relevant proprietary files: .avl, .lyr, .mxd

Proprietary map project and layer representation files tend to be less open and often lack forward compatibility across major software revisions.

Export to SVG or other open, XML-based option

XML structures need to be well understood in order to support permanent access (as opposed to requiring digital archaeology). Widely accepted profiles or standards would be needed.

Image-based approachesGeneration of images using map book tools, or harvest existing map books

Results in a complex set of images linked through HTML grids. Compatible with capture of large extents.

Automate capture of map book equivalents from Web Map Server (WMS) servers

Potential for automated, agent-based capture. Availability of WMS services increasing.

Export layout or map to image Does not provide the flexibility to handle large extents that the map book approach does, but does present the opportunity to capture agency-provided added value work.

Insets show basicgeospatial data for

Raleigh, NC, with (left)and without (right)

cartographic additions

Imagery Topology Vector Data

Poster presented by Rob Farrell, Geospatial Initiatives Librarian, NCSU LibrariesFor more information, please visit www.lib.ncsu.edu/ncgdap

Archiving Spatial Databases Archiving Cartographic Contribution