The "Coast to
Direct Map Request
The Tiger Mapping Service has been designed around an open architecture
for maximum flexibility. The TMS Map Browser is not the only way of
accessing TMS-generated maps; it is only an example application. By
using the syntax below, anyone can request maps directly via a URL.
This makes it possible to include TMS maps in your own documents, or even
your own interactive mapping applications, because a "live" TMS map addressed using the URL described below can be used
in exactly the same manner as a static GIF image (i.e., in a
Basically, a map can be requested directly from TMS by using the following
where the parameters can be any or all of the following, separated by ampersands:
For your information, all maps are projected using a simple sinusoidal projection
centered on the central meridian. This makes the response quick, but also makes
it difficult to mosaic maps together. In this projection, distances are true
to scale horizontally, vertically along the central meridian, but not diagonally.
- the longitude, in decimal degrees, of the center of the
map. Remember that
longitudes for the Western Hemisphere are negative numbers. Longitudes for the
contiguous U.S. range between about -67 and -125 degrees.
- the latitude, in decimal degrees, of the center of the map.
Latitudes for the
contiguous U.S. range between about 24 and 49 degrees.
- the desired width, in decimal degrees of longitude, of the
the map. The actual coverage of the map may vary slightly from this number, due
to fitting the requested coverage to the shape of the image.
- the desired height, in decimal degrees of latitude, of the
coverage of the map. May turn out slightly different, for the reason above.
- the image width, in pixels. If none is specified, the
default is 512.
- the image height, in pixels. If none is specified, the
default is 256.
- if included, the legend graphic is returned rather than the map.
- if included, places one or more markers on the map at
the longitude and latitude given. The label, if included, is the text to be
displayed adjacent to the marker (the label must by URL-encoded, i.e., replacing
spaces with +). The symbol is the graphic symbol used to
mark the location. Currently, the following symbols are supported:
(default if none specified),
More than one marker can be placed, by separating the marker parameters with a
semicolon (;). However, the allowable number is limited by the 256-character URL
limit (which amounts to about 6-8 points).
- this gets over the above marker limit by allowing the requestor to submit an
entire list of points. This list is placed in a separate file, which must be in a
place visible to the world via HTTP (i.e., on your own web server). The URL given
is the address used to retrieve this file. The format of
the file is as follows:
#tms-marker (a flag on the first line to identify the file type)
lon,lat:symbol:label #optional comments after a pound sign
lon,lat:symbol:label #labels are optional, but you still need the colon
lon,lat:symbol:label # after the symbol.
where lon, lat, symbol, and label are defined as above (except that
the label is not URL-encoded). An example marker file
might be useful.
- forces individual feature layers to be displayed, or not displayed, respectively.
These fields override, but don't replace, the natural layer selection (i.e. layers
not mentioned may still be displayed or not, depending on the default scheme). The
following layer names are valid:
GRID (graticule, along with margin labelling)
BACK (blue background)
CITIES (labels on places)
states (state boundaries, which also form white land fill over BACK)
counties (county boundaries)
places (cities and towns)
majroads (expressways and other highways)
streets (normal streets-don't turn this on when zoomed way out)
water (water bodies, including linear streams and areal features)
shorelin (lines bordering areal water bodies)
miscell (miscellaneous features, including parks and schools)
- selects a geography level for drawing thematic statistical maps (must
be used with tmeth and tvar). The available level codes are:
msa (1991 Metropolitan Statistical Areas)
con_dist (1992 House Congressional Districts)
places (cities, towns, and CDP's)
mcd (Minor Civil Divisions-New England only)
tracts (Census Tracts: 15-20 city blocks)
censusb (Census Block Groups: 4-5 city blocks)
- selects a statistical variable to use in thematic maps (must be used
with tlevel and tmeth). So far, not all the 1990 census variables are
in the database, but the following can be used:
famsize (Family Size: persons per family)
hhsize (Household Size: persons per household)
density (Population Density: persons per sq mi)
income (Median Family Income)
p0-4 (% of Population Age 0-4)
p5-9 (% of Population Age 5-9)
p10-19 (% of Population Age 10-19)
p20-49 (% of Population Age 20-49)
p50-64 (% of Population Age 50-64)
p65- (% of Population Age 65 and over)
white (% of Population White)
black (% of Population African-American)
indian (% of Population American Indian)
asian (% of Population Asian)
hispanic (% of Population Hispanic)
other (% of Population from other ethnic groups)
owners (% of Households Owner-Occupied)
renters (% of Households Renter-Occupied)
- tmeth=q or i
- selects the classification method to use in thematic maps (must be used
with tlevel and tvar). Can either be "q" for Quintiles (5 classes of equal
size) or "i" for Equal Interval (5 classes with an even range of values).
These classes are calculated over the entire country, not just the map area.
Quintiles tend to provide better contrast between values around the average,
while Equal Interval tends to emphasize the extremes (but this is not a hard
and fast rule).
Here are some examples of usage for the Direct Map Request feature:
- The Mall in Washington, D.C., with markers on the White House and Capitol:
- The 48 contiguous United States:
- The Northeastern United States:
- Manhattan, New York City:
- Legend for above Manhattan map:
- A region with several cities marked:
If you have feedback, please check out the Mapsurfer Feedback page.
If you have questions, please check out the service FAQ page.
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Last Revised: Friday, 12-Sep-97 13:41:45