TxDOT Urban Files,  Spring 2002

The documentation for the original mapping files received
from the Texas Department of Transportation follows.  Please
note that these files were originally created in Intergraph
Microstation format and TNRIS processed the files into 
Arc/Info coverages.  Documentation on this process can be
found at the end of this file.



Texas Department of Transportation (TxDOT)
Digital County/Urban Map Files


SUMMARY:  The TxDOT mapping files are in two map series, the 
County Map series is to support map publication and the 
Urban Map series is to support Geographic Information Systems 
(GIS).

I.  Map Content

The transportation information in the TxDOT county/urban map 
files were digitized from USGS 7.5 minute quadrangles.  
Updates are made using TxDOT highway construction plans, 
aerial photographs, official city maps and field inventory data.  
These files contain many of the features found on 7.5 minute 
quads, except for contour lines, fence lines, jeep trails, 
electrical transmission lines, oil and gas pipelines and 
control data monuments.

These files contain all line work and annotation done at the 
4"=1 mile or 1320 ft scale. The urban file is unbroken but 
unlike the cnty file this file does not end at the county line 
and may not cover the complete county. 



II.  Map Projection

            Projection geographic
            Units dd
            Datum nad83

III.  Positional Accuracy

Urban Map Series:  (County Number)urban.dgn

The Urban Map Series is the digital basemap that will become 
the Geographic Information System for TxDOT.  The features in 
this state wide coverage have been digitized from USGS 7.5 minute
quadrangles.  City limit lines and new roads are updated prior to
a map sheet being published.  The Railroads may be displaced 
laterally as much as 200 feet from their true position when 
they parallel a road.  The hydrology has been generalized except 
for the lakes that have been digitized at the mean pool elevation 
as described on the USGS 7.5 minute quadrangles.  

These files contain all line work and annotation done at the
4"=1 mile or 1320 ft scale. The urban file is unbroken but
unlike the cnty file this file does not end at the county line
and may not cover the complete county.




IV.  County Map Levels                                        

TxDOT uses the following level structure for its county/urban maps.
These following features are found in (county number)cnty.dgn and
(county number)urban.dgn files

Feature							Level

Highway Number						1
Highway Boulevard					2
Frontage Road / Ramp					3
Highway Boulevard Centerline				4
Highway in City						5
Pedestrian Overpass					6
Blank							7
Highway Rural						8
Bridges on Boulevard Highways				9
Highway Shields						10
Bridge on Highways in Cities				11
Bridge on Rural Highways				12
Blank							13
Culture Names (Most of the Annotation)			14
City Street Boulevards					15
City Street Boulevard Centerline			16
Concrete Ford						17
City Streets						18
Street Names (on Urban files only)			19
County Road Bridges					20
Not County Maintained Roads				21
Earth County Roads					22
All Weather County Roads				23
Paved County Roads					24
Rural Subdivision Boulevard Centerline			25
Rural Subdivision Boulevard				26
Railroad: Main Line, Pattern and Name			27
Railroad Name						28
Railroad: Spur Line, Pattern				29
Blank							30
Railroad Bridge						31
Blank							32
Blank							33
Water Feature Names					34
Flume							35
GIWW Channel Centerline					36
Intermittent Streams					37
Flowing Streams & Small Rivers				38
Lakes							39
Medium Flowing Rivers					40
Large Flowing Rivers					41
Intermittent Lakes					42
Inundation Line						43
GIWW Canal (through water) & Channel Names		44
GIWW Canal (through land) & Barge Symbol		45
Dam							46
Mask for Barge Symbol					47
Escarpment, Bluff					48
Prominent Peak Symbol					49
Border Sheet Match Points				50
State Line Monument					51
Boundary Lines						52
Airport Runways						53
Public Facility Symbols					54
Culture & Government Symbols				55
Blank							56
Town Symbols, City Names and Population			57
City Limit Lines					58
Bubble Inset Lines					59
Asterisks and Mileage between Points			60
Asterisks Masks						61
Blank							62
Non-Plotting Information				63




VI.  Contacts for Additional Information

If further clarification is needed please contact: 

Texas Department of Transportation 
Transportation Planning and Programming
P. O. Box 149217
Austin, TX 78714-9212

Director of Data Management, 
Kim Hajek (512) 486-5052

Mapping Manager, 
William Watson (512) 486-5094



TNRIS PROCESSING:
TNRIS received the files in .dgn format and converted
the files to coverages using the 'igdsarc' command. 
The coverages were then copied to single precision,
cleaned as line data and joined with the appropriate
.acode files.  Next an item called "FEATURE" was
added to the .aat files and populated with the
written description of the feature (i.e. Highway Rural,
City Streets, etc). The numeric code for these features 
can be found in the item 'IGDS-LEVEL'.  Annotation, originally
in one subclass was moved into unique subclasses for each
feature type.  Lastly the 'projectcopy' command was used
to add projection information to each coverage and the 
coverages were exported and zipped with this readme file. 


Questions about the TNRIS processing of the data should
be directed to:
Marcy Berbrick
TNRIS Information Services
512/475-2308, 
mberbric@tnris.state.tx.us.
