MSDIS serves more than 12,000 data files via FTP. The files
have been gzipped (compressed) for faster downloading. Gzip
compresses ASCII files by about 70%. If you are unfamiliar
with
gzip or need to download software able to decompress gzipped files,
check out the GZIP HELP PAGE.
Examples of how to use GNU's gzip program are also available.
Most of the data on the FTP server are organized by Geography
i.e. by State or by County extent. These
data can easily be accessed in three main ways:
1. Via the data search tool (http://msdisweb.missouri.edu/datasearch)
The data search tool utilizes a web form allowing querying
of a database of MSDIS metadata records. The search can be
refined by state or county geographic extent and by searching
for key words in the metadata records.
2. Via custom web interface
to the FTP server using a web browser
Many of the datasets served by MSDIS have custom built web
interfaces to allow easy location of data with links to the
FTP location for download. The "Data Resources" navigation
area on the left side of all the pages under the "Data" tab
of this page contains links to all of these interfaces.
3. Directly from the FTP server
using a web browser or FTP client software or using command
line FTP
If you are comfortable navigating an FTP server you can do
so. Just choose your method, either from your web browser,
from FTP client software such as WS-FTP or from the Command
prompt. The URL of the public area of MSDIS FTP is http://www.msdis.missouri.edu/msdisdata/pub/
Data formats
ArcInfo
Interchange files
With a few exceptions the GIS data available from MSDIS are
ArcInfo interchange files which are used to transfer coverages,
INFO data files, text files such as AML macros, and other ArcInfo
files between various machines. An interchange file contains
all coverage information and appropriate INFO file information
in a fixed-length, ASCII format. It can be fully or partially
compressed and uncompressed ASCII depending upon the EXPORT
option used.
Most files are in export (.e00) format. Tabular datasets are
available in INFO and .dbf formats. You will need ArcGIS or
ArcView from ESRI,
CAD, mapping or Geographic Information System software that
can read ArcInfo export files to use the datasets.
The files have been gzipped (compressed) for faster downloading.
Gzip compresses ASCII files by about 70%. If you are unfamiliar
with gzip or need to download software able to decompress gzipped
files, check out the GZIP
HELP PAGE.
Shapefiles
We receive many enquires regarding the lack of availability
of data in Shapefile format for use with ArcView. Currently,
only a few shapefiles are available. However, it is a straightforward
process to bring a ArcInfo interchange file into ArcView
using the Import71 module. Import71 comes with ArcView.
For non ArcView users, Import71 can be downloaded from
a number
of sources on the internet including:
Import71 Help
We have created a textual help page for using Import71:
http://msdisweb.missouri.edu/data/import71help.htm
There are many other comprehensive on-line tutorials for first
time users
of
Import71
giving step
by step
instructions
with
screen
shots. An internet search will quickly point you in the
right direction. To save you time here are few links:
Other Formats
Data on MSDIS are provided in several other formats for specific
applications. For example, imagery (raster)
data in GeoTIF format or MrSID format,
Census
2000 maps
in Adobe Portable Document Format, NRCS soils maps in Shapefile
format. Free viewers are available for most of these formats
but will still need GIS software
to make full use of them.
The
following
table provides a quick summary:
| File Extension |
File Type |
Example Data Type |
| .pdf |
Adobe Acrobat
http://www.adobe.com |
Census 2000 official tract & voting district
outline maps |
.sid
.sdw
|
MrSid File
MrSid Georeference File
http://www.lizardtech.com/ |
DOQQ County Mosaics
& National Agricultural Imagery Program |
.tif
.fgd
.tfw |
Tagged Image File Format
USGS Metadata Document File
TIFF Georeference File |
DRG |
| .dbf |
Database File |
Various |
.map
.tab
.id
.ind
.dat |
Map File
ArcView Lookup File
DBase IV index
Data file |
Flood Insurance Maps |
.sbn
.prj
.shp
.sbx
.xml
.shx |
ArcView Spatial Index
ArcView Projection
ArcView Shapefile
ArcView Shapefile Index
Extensible Markup Language
ArcView Shapefile (Points) |
Missouri DNR Geology / Hydrology |
.mdb
.shx |
Microsoft Acess Database
ArcView Shapefile (Points) |
NRCS Soils Data Viewer |
Projections
UTM
Most data on MSDIS are projected in the UTM (Universal Transverse
Mercator). This system is a specialized application of the
transverse Mercator projection which is both cylindrical
and conformal. It divides the world into 60 numbered zones,
both north and south, separated by the equator. Each zone
spans six degrees of longitude and has its own central meridian.
This system was adopted by the US Army Map Service in 1947
for their use in worldwide mapping and continues to be used
worldwide. Most of Missouri falls into UTM zone 15 but part
or all of 8 counties in the boot heel area of the state fall
in Zone 16.
Stateplane
Some MSDIS data are provided in stateplane. The State
Plane coordinate system is not a projection. It is a coordinate
system that
divides all fifty of the United States, Puerto Rico and the
US Virgin Islands into over 120 numbered zones. Construction
of a coordinate system for each zone is based on one of three
projections: the Lambert Conformal Conic, the Transverse
Mercator or the Oblique Mercator. The plane coordinate system
used in Kansas is based on the Lambert Conformal Conic projection
with two standard parallels for each zone--North and South.
Each zone has an assigned USGS code, each having a designated
central origin that is specified in degrees. Generally used
on 7.5 and 15-minute topographic quadrangles.
North American Datum
(NAD)
There are two phases of the North American Datum - NAD27 and
NAD83 - one local the other geocentric. Most data on MSDIS
is NAD83. Local datum align a spheroid to closely fit the earth's
surface in a particular area. A point on the surface of the
spheroid is matched to a point on the earth's surface - this
point is the origin of the datum and has fixed coordinates.
All other points are calculated from the origin. The North
American Datum of 1927 is a local datum based on the Clarke
1866 spheroid and centered on an area named "Meades Ranch" in
Kansas.
Geocentric datum relate coordinates to the earth's center
of mass. Such datum have been improved by modern satellite
data. The North American Datum of 1983 is based on the modern
GRS 1980 ellipsoid - almost identical to the most widely used
WGS 1984 ellipsoid which is also geocentric. Both earth and
satellite data went into the determination of this datum. Because
raw GPS data is based on the WGS 1984 ellipsoid, the data is
also compatible with NAD83.
Metadata
Metadata are included in the .e00 files you can download
from MSDIS. The metadata can be examined using document.aml
in ArcInfo. XML format is discoverable via the Data Search
Tool. HTML format is accessible from links via the Dataset
Listing Page. See the Metadata pages.
