ADL Digital Data Examples
The Alexandria
Digital Library is loading, over
time, the collections of many participants. This includes spatially indexed
collections of the U.C. libraries and archives, selected California State
University holdings, state and federal agency publications and private research
contributions. Geographically our plan is to grow the georeferenced holdings
from California outward. We are loading synoptic datasets first followed by
more detailed narrower-scoped materials. Detailed digital information at the
state level is widely scattered, thus ADL will focus on existing historic maps,
reports and aerial photography of California building out from Santa Barbara to
other state locations. Another equally
important consideration will be the condition of the original materials. Those
objects in poor condition will be scanned and loaded first so as not to lose
any historic content.
Three categories
of "collections" are initially being loaded into the Alexandria
Digital Library (ADL). They are:
Collections of metadata for both on and
off-line data holdings
A gazetteer (place name index) of 6.5 million
earth locations, and
Digital data that can be linked to, browsed,
and downloaded to desktop applications.
For
term definitions, shown in black Italics, see the glossary at the
end of this document.
The ADL metadata
collections are comprised of bibliographic records at the item level. This
means that each data object represented in the library has its own catalog
entry. As an example, each of the 65,000 topographic maps of the United States
has its own entry in the catalog. These records may also have what is termed a
parent catalog entry; information that is shared in common with all data
objects belonging to a single publication project. Each record describes a
library data object whether online or still residing in its paper form. The ADL
catalog contains about 750,000 bibliographic records at this time.
The ADL
gazetteer, another name for a place-name index, allows a user to find earth
features by typing in the name associated with that feature, e.g., find the
city of Santa Barbara or find all references to the name "Santa
Barbara" worldwide. The gazetteer database may be used as a spatial
finding aid or as a stand-alone reference tool.
The ADL data
archive is a growing set of digital files that may be accessed online.
Initially ADL plans to focus on California with a few other demonstration sets
of other parts of the world. These California data are comprised of digital
map, text and imagery files of varying detail starting from a space perspective
and "drilling-down" to detailed earth features (see footprint diagram
below). These datasets are briefly described below starting with those with the
least earth detail and proceeding to those with the most detail. In the
examples below, imagery datasets are listed first, followed by mapping
datasets. No example of a spatially referenced text document is supplied in
this overview.
SPACE-PIX -
These space-shuttle images cover selected regions of the Earth and give a
synoptic but minimum detailed look at selected Earth locations: expect detail
at the level of cities and mountain ranges. These images differ from the
following AVHRR image in that they are color and are often
captured at an oblique angle. ADL currently has about 3000 of these images
scattered around the earth. The smallest ground detail that can be recognized
is about 2 kilometers.
AVHRR imagery
is constantly changing. It is captured from a satellite at regular intervals
during the day and night. This imagery has a ground detail of about 1 kilometer and is in black and white. Since this data is made available via ADL in
close to real time, only the most current images are offered. The data is
linked via ADL from a remote Internet site. It takes one or two images to cover
all of California. This data may be used to observe weather conditions, track
forest fires, or the effect of flooding from El Nino.
Thematic Mapper
Imagery [TM] is medium scale satellite data. It has a ground detail of about 20 to 30 meters and has 7 channels of image data that
may be viewed singly or in combinations. The data is used for vegetation
analysis, urban planning, geology and many other forecasting and research
areas. ADL has georectified tiles for all of
California. Please refer to fig. A for ground-area footprint. Currently there
are about 30 tiles that cover all of California.
Spot Images
for California are also satellite data and ADL contains tiled images for the
whole state. This data is only licensed for U.C. research. The images are black
and white tiles with a ground detail of about 10 meters. There are
about 185 tiles in this dataset that cover all of California.
Digital Orthophoto Quadrangles [DOQ] are digital "image-maps"
in that they coincide with existing printed USGS Topographic maps but reveal
photographic features. They have a ground detail of about 1-meter. Currently, about half of California, mostly urban areas are complete.
ADL has loaded about 7,000 files of the 15,000 that will be available when the
publication is complete in 2001. This imagery is georectified and can thus be
used with standard USGS topographic maps.
Selected
detailed historic
aerial photography of California
are being scanned. This is an ongoing program for making unique historic
California aerial photography housed at UCSB and other archive locations web
available. Currently about 4,000 images have been scanned ranging in dates from
1928 to the present. The ground detail of these images is about ½ meter. The geographic region being scanned by ADL in 1998 is urbanized
Southern California. This will be expanded to other California sites as
contributions from other participating archives are added to ADL.
ADL
will also provides access to various map sets, including the examples below.
Two types of data are initially being loaded by ADL; digital elevation models
(contour relief maps) and scanned topographic maps. Complete sets for
California will be available through ADL. Please refer to figs. A and B for
geographic footprint information.
Digital Elevation Models [DEM]
are available in two scales; 1:250000 and 1:24000. The former has a ground
detail of about 80 meters and the latter a detail of about 30 meters. They are used for showing physical terrain and as a basic level
dataset for many mapping applications. When used with Spot or DOQ images a 3D
model of an area may be constructed. ADL will provide access to both datasets.
The series contain about 3350 files for the State.
Digital Raster Graphic [DRG] maps are scanned topographic maps at a scale of 1:24000. They have
a ground detail of about 30
meters and are produced by the United
States Geological Survey. Each map is georectified and may be used in
conjunction with the corresponding DOQ data. Currently, ADL is working with the
California Teale Data Center and the USGS to make these digital maps available.
There are about 3300 files for California in this series.
Other datasets being loaded for
educational instruction
Sierra Nevada Ecosystem Project (SNEP) This dataset is comprised of maps, GIS
coverages, text and images. This NSF funded research project was completed in
1997 and represents the eco-environment of the Sierra Nevada geographical area.
It covers large sections of California and Nevada wilderness and is actively
used for research and teaching.
CIA Country Maps
These scanned maps of various scales cover all of the worlds countries. They
represent a basic worldwide dataset for educational instruction. There are
about 350 map files accessible through ADL
Glossary of Terms
AVHRR Advanced Very High Resolution Radiometer: an image sensor
on an earth satellite.
Channels multiple images captured by imaging sensors of the same
location, at the same time, but at different wavelengths of light.
Datasets groups of data objects that may be described as a single
unit e.g., Encyclopedia Britannica.
Desktop Applications personal computer applications
such as PhotoShop or Microsoft Word.
Gazetteer place name index showing an earth feature such as a city
along with its geographic location.
Georectified spatial data that has been computer processed so
as to match Earth locations exactly.
Image-Map - a map that has its features presented photographically
rather than hand or machine drawn.
Metadata information about a data object; a bibliographic catalog
record describing the data unit.
Tiles data that has been cut into "pages" so they can
be viewed one-at-a-time or stitched together.
Topographic maps maps that show contour lines of
equal elevation in addition to other Earth features.
Footprint Diagrams
Last updated: 20090714