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TIGER Data Analysis (Map)
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Jeff Dempsey
Chris Reynolds
* OVERVIEW
- TIGER/Line data is cartographic data provided from Census Bureau.
- A prototype Visual C++ program written to read the TIGER/Line data has
proven that we can read the data.
* DATA FORMAT
- 1990 Census TIGER/Line file
- Data is an extract of selected geographic and cartographic
information from the Census Bureau's TIGER data base.
- ASCII format
- Record Files are named TGR13121.F4<1-R>
- The record types are as follows:
1. Basic Data Records
- Line segment endpoints in Long/Lat
- Name ( EX. Old National )
- Type ( EX. Hwy )
2. Shape coordinate points.
- Additional points for line segements in record type 1 that
are not straight lines.
3. Additional Decennial Census Geographic Area Codes
4. Index to Alternative Feature Names
- Additional feature names for line segments in record type 1.
5. Feature Name List
- List of additional feature names.
6. Additional Address Range and ZIP code Information
7. Landmark Features
- Names and locations (Long/Lat) of landmarks.
8. Area Landmarks
- Ties landmarks to polygons (Areas).
A. Additional Polygon Geographic Area Codes
I. Area Boundaries
P. Polygon Locatioon
- Interior points of polygons.
R. Record Number Range
- Range of record numbers for all records.
- Additional information for each record is contained in the
RT<1-R>DD.ASC files. These files contain the field names,
data types, size, beginning and ending character position,
and descriptions for each record type (Table layout).
WARNING: Some of the beginning and ending character positions
are incorrect so double check if you use them in some type
of conversion.
- Additional useful information related to the TIGER/Line data
is contained in TIGERABS.ASC and TECHDES.ASC files.
* AVAILABLE SOURCE CODE / API's
- Source code available for reading and displaying TIGER/Line data for
Macintosh. (GTRI)
- Code is not commented very well.
- Tried to convert the code to a PC platform but ran into
trouble with Macintosh specific system code. Found the Macintosh
specific code is embedded so deeply that converting the code
would take more time than writing new code from scratch.
- Looked and failed to find PC source code/API's to read TIGER/Line data.
- Found two OCX controls to display TIGER/Line data, neither
of them were free.
Sylvan Map Products - $495
EMap Technologies - $295 (Data must be converted to MAPInfo format)
- Also found several web sites that query and display TIGER/Line data.
* READING/CONVERTING/RENDERING DATA
- Because the data is in ASCII format and the descriptions of the
individual TIGER/Line data records are given, the data can be read
in, converted, and stored accordingly.
- Polylines can be formed using the record types 1 and 2.
- Landmarks can be formed using record types 7, 8, and P.
- Feature names and types can be associated to polylines using
records 1, 4, and 5.
- All of this data can be rendered to provide a "map".
* PROBLEMS
- Options are being discussed for arranging the database so that it can be
searched efficiently. The large size of the data presents a few problems.
- The 1990 TIGER/Line data is currently being used. We are unable to download
the new 1994 TIGER/Line data, but will see if we can get it through our
library or through our sponsor (Kirk Pennywitt).
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Garmin GPS 45 (Position)
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Marty Mathis
* OVERVIEW
- GPS (Global Positioning System) is a system that uses satellites (and
possibly other beacons) to determine position on earth.
- Garmin GPS 45 accuracy estimated to be about 30 meters
- We can possibly obtain software that can improve this accuracy
* HARDWARE
- Differential GPS uses a relatively local beacon to help improve accuracy.
Differential only works on or near the coast (possibly some other large
bodies of water)
- The Garmin GPS 45 comes with 9 pin serial port and sould easily be
hooked into the fujitsu or any other portable PC.
- A newer model of GPS has been obtained (Garmin GPS 45 XL). I have not
tested this GPS at all however. I assume it performs much the same as
the 45 except maybe a little better.
* SOFTWARE
- Have obtained Garmin GPS PC software, but I have not tested it at
all. I would like to evaluate it on a portable as soon as possible.
- Have made contact with a man at GTRI who has written a Visual Basic
application that takes the coordinates of the GPS and using some
averaging technique to achieve under 5m accuracy. This would be the best
thing for our project if this works out like it has been described to
me. I am in the process of obtaining the source code now. I will turn
it over as soon as I have it. This code could give our group a great
deal of breathing room in the GPS area and allow our programmers to
concentrate heavily on TIGER/Line data programming.
- I am not sure what the transfer rate from the GPS to the PC. I
don't consider this to be a huge software issue.
* PROBLEMS
- If the Visual Basic application that averages GPS values cannot be obtained,
more work will be needed in order to achieve accuracy on a local level
(either by programming an averager or by using differential GPS).
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