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<TD id=header colSpan=5><IMG height=68 alt="Harpers Ferry Center"
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<DIV id=printlogo><IMG height=78
alt="National Park Service, Harpers Ferry Center"
src="Harpers Ferry Center NPS Maps_files/arrow-header-print.gif"
width=588> </DIV><A
href="http://www.nps.gov/hfc/carto/index.htm">NPS Maps</A> > <A
href="http://data2.itc.nps.gov/hafe/hfc/carto.cfm">Find a National
Park Service Map</A> > <A
onmouseover="message('Search Results');return true;"
href="javascript:parent.history.back()"></A>Data Sources &
Accuracy</TD></TR>
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<TD colSpan=5>
<H1>Data Sources & Accuracy for NPS Maps</H1></TD></TR>
<TR>
<TD><IMG height=173 alt="Section of Zion National Park map"
src="Harpers Ferry Center NPS Maps_files/carto-zion.jpe" width=173
border=1>
<P class=caption>Section of Zion National Park map, Utah.</P></TD>
<TD
background="Harpers Ferry Center NPS Maps_files/dotted-line-vert.gif"> </TD>
<TD id=primary>
<P>National Park Service maps are graphical products designed for
general reference, orientation, and route finding. Do NOT use these
maps for backcountry hiking, navigation, GPS referencing,
mountaineering, and other specialized activities�use US Geological
Survey (USGS) topographic maps instead. National Park Service maps
do NOT have legal authority. They are NOT official boundary
documents, and, because of their small scale and generalized nature,
do not necessarily show small outlying park areas and private
inholdings.</P>
<P>Most of the digital maps at this site derive from traditionally
produced maps revised and printed during the past 20 years. An
increasing number of more recent maps, however, derive from
Geographic Information System (GIS) and <A
href="http://edc.usgs.gov/geodata/">USGS Digital Line Graph (DLG)
sources</A>.</P>
<P>Because of graphical modifications, it is not appropriate to
import the maps on this site into GIS applications.</P></TD>
<TD
background="Harpers Ferry Center NPS Maps_files/dotted-line-vert.gif"> </TD>
<TD id=related>
<H3>RELATED LINKS:</H3>
<P><A
href="http://erg.usgs.gov/isb/pubs/factsheets/fs17199.html">National
Mapping Program Standards �</A></P>
<P><A href="http://geonames.usgs.gov/gnishome.html">U.S. Board on
Geographic Names �</A></P>
<P><A href="http://edc.usgs.gov/geodata/">USGS Digital Line Graph
(DLG) sources �</A></P>
<P> </P></TD></TR>
<TR>
<TD><IMG height=175 alt="Example of NPS park map linework"
src="Harpers Ferry Center NPS Maps_files/carto-linework.gif"
width=175>
<P class=caption>Example of NPS park map linework.</P></TD>
<TD
background="Harpers Ferry Center NPS Maps_files/dotted-line-vert.gif"> </TD>
<TD id=primary>
<H2>Linework</H2>
<P>The linework on National Park Service maps originates from USGS
sources that meet <A
href="http://erg.usgs.gov/isb/pubs/factsheets/fs17199.html">National
Mapping Program Standards</A>. However, manual production processes
prior to map digitization often diminishes the accuracy of the
original data. Factors contributing to inaccuracies include the
stretch and shrinkage of USGS paper maps, camera lens distortion
when photographing a composite base map, and manual drafting of
lines.</P>
<P>The National Park Service uses stringent map digitizing standards
to minimize the introduction of additional errors when digitizing
traditional maps. For example, the size difference between digitized
maps and the traditional bases from which they derive never varies
more than 0.005 inch across the full extent of the map. The map
digitization standards also preserve the visual character of
features. For example, sinuous line strings comprised of tight
Bezier curves depict streams and graceful Bezier arcs represent
major roads.</P>
<P>Linework on the more recent maps derive from GIS and USGS DLG
sources, albeit in a modified form. Typical modifications to
linework (and other vector data) include removal of excess and/or
inaccurate anchor points, conversion of linework to bezier curves,
and slightly changing the position of lines in congested areas to
improve legibility.</P>
<P>Be aware that linework running off the printed area of maps is
sometimes fictitious and serves only as bleed for cropping. Some
classes of map data, especially hiking trails, derive from
non-surveyed or field-checked sources.</P></TD>
<TD
background="Harpers Ferry Center NPS Maps_files/dotted-line-vert.gif"> </TD>
<TD> </TD></TR>
<TR>
<TD><IMG height=175 alt="Example of NPS park map shaded relief"
src="Harpers Ferry Center NPS Maps_files/carto-shaded-relief.gif"
width=175>
<P class=caption>Example of NPS park map shaded relief.</P></TD>
<TD
background="Harpers Ferry Center NPS Maps_files/dotted-line-vert.gif"> </TD>
<TD id=primary>
<H2>Shaded Relief</H2>
<P>Shaded relief is the graphical portrayal of topography in a
natural manner using modulated light and shadows. Shaded relief on
most National Park Service maps derives from manual techniques using
airbrush, pencil, and paints applied to stable base materials. More
recent shaded relief, however, derives from digital production.</P>
<P>The registration of scanned shaded relief art to drainages and
other map linework occurs in Adobe Photoshop. In the event of
registration discrepancies, the NPS modifies the shaded relief�using
the standard array of scaling, distortion, and paint tools in
Photoshop�to ensure a close fit with the linework. We never alter or
reposition linework to fit shaded relief.</P>
<P>The resolution of shaded relief at final size is generally 200
dpi, intended for printing with 175 lpi screens. Our testing has
shown that higher resolution adds no additional relief detail, but
only increases files to unwieldy sizes.</P></TD>
<TD
background="Harpers Ferry Center NPS Maps_files/dotted-line-vert.gif"> </TD>
<TD> </TD></TR>
<TR>
<TD><IMG height=85
alt="Examples of NPS park map cartographic symbols"
src="Harpers Ferry Center NPS Maps_files/carto-point-symbols.gif"
width=175>
<P class=caption>Examples of NPS park map cartographic
symbols.</P></TD>
<TD
background="Harpers Ferry Center NPS Maps_files/dotted-line-vert.gif"> </TD>
<TD id=primary>
<H2>Point Symbols</H2>
<P>Locator dots show the general location of points of interest. The
position of dots for sites covering large areas, such as campgrounds
and picnic areas, are approximate. To enhance legibility, features
represented by point symbols on the map are exaggerated in size
compared to their true size at map scale.</P>
<P>Elevation dots come from USGS sources. To register summit
elevation dots with shaded relief bases, we sometimes adjust the
position of the dots slightly.</P></TD>
<TD
background="Harpers Ferry Center NPS Maps_files/dotted-line-vert.gif"> </TD>
<TD> </TD></TR>
<TR>
<TD><IMG height=100
alt="Examples of NPS park map scales, milage indicators, and point elevations"
src="Harpers Ferry Center NPS Maps_files/carto-scales.gif"
width=175>
<P class=caption>Examples of NPS park map scales, milage indicators,
and point elevations.</P></TD>
<TD
background="Harpers Ferry Center NPS Maps_files/dotted-line-vert.gif"> </TD>
<TD id=primary>
<H2>Numbers and Scale</H2>
<P>Elevations in feet come from USGS maps, from which we calculate
the metric elevations rounded to the nearest whole number.</P>
<P>Mileage distances derive from odometer readings rounded to the
nearest whole number, as are equivalent distances in kilometers.</P>
<P>Because National Park Service maps must fill the available space
on a brochure, they seldom match the scales of standard USGS map
series. To calculate a numerical scale, use the bar scale found on
almost every map.</P>
<H2>Place Names</H2>
<P>Geographic feature names derive from USGS maps and conform to <A
href="http://geonames.usgs.gov/gnishome.html">U.S. Board on
Geographic Names</A> standards, although discrepancies may exist.
Check with the Board to confirm all spellings.</P>
<P>Other naming discrepancies may exist for categories of features
not covered by the Board such as the names of trails, roads, park
facilities, and points of interest. Name changes to these features
are not uncommon; National Park Service maps generally show the most
recent names endorsed by park officials.</P>
<P>National Park Service maps use diacritical marks for spelling
Hawaiian place names where approved by the Board on Geographic
Names.</P>
<P>Note: The National Park Service uses a proprietary font for
labeling Hawaiian maps that is not released publicly. Due to font
substitution, diacritical marks do not appear on downloaded maps.
Check printed National Park Service maps for the correct spelling of
all Hawaiian place names.</P></TD>
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<TD> </TD></TR>
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<TD>Author: Harpers Ferry Center<BR>Last Updated: Tuesday, 27-Sep-2005
16:00:12 Eastern Daylight
Time<BR>http://www.nps.gov/hfc/carto/data-sources.htm</TD></TR></TBODY></TABLE></BODY></HTML>