Evening star. [volume] (Washington, D.C.) 1854-1972, 1927-01-23

with the growth OF aviation has
come an increased demand for maps
to guide aviators on long flights. The
Department of Commerce has been
charged with furthering the interests
of civil aviation, and since the prepa-
ration of route maps will undoubtedly
be one Of the most important methods
of doing this. the Coast and Geodetic
Survey Is preparing 80 take the air, -
as 1t we're
Col. E. Lester Jones, director of the
Coast and Geodetic Survey, points out
that less than half the area of the
United States Is covered by the kind
Of maps needed by aviators. And
pilots Of airplanes must have maps,
A pilot who is frequently out of sight
Of land must be guided over the land
even as the navigator Of ship Is
guided over the sea by charts and
aids to navigation.
Col. Jones goes on to say that the
aviator who cannot see the ground
must depend upon barometer, but
| this is act to give elevations above
the sea instead OF the actual land
| surface. He may. therefore. believe
himself to be several.thousands of feet
above the earth, wien as a matter of
| fact he is in imminent danger of strik-
Ting mountain slope or peak. There
| fore. maps of aerial routes must in
some manner indicate the elevation
of the ground Also, topogra phic
features such as railroads. highways.
| rivers. cities, woods ano open country
| should he shown in their correct
| shapes and positions.
| Such information as the above may
| be obtained from toposra phic maps.
| The trouble is. however, that at the
| present time only about 40 per cent OF
| the area of the country is covered by
such maps. Also, much of this should
| be resurveyed in order to bring the
maps IN to date, since they were sur
veyed 40 or more years ago.
SuppIementing Topographic Maps.
Col. Jones continues THE Coast
and Geodetic Survey for years has
been extending accurate triangula ton
| a nd leveling over the Interior of the
country for surveying, mapping and
| other engineering uses With this tri-
Angtilation the highway system and
| the railroad system Of the country can
| he correlated and placed in at least
| approximately their right positions on
maps The elevation furnished by the
survey can be used for furnishing
mean sea level datum for surveying.
mapping and engineering operations.
| The topographic map cannot be accu-
rately made II the fundamental con
| troll work of the Coast and Geodetic
Survey in the form Of leveling and tri-
ang,ilation has not been completed for
the area that is TO be mapped"
Few large areas of the United States
have continuous topographic maps.
and something should be done about
| this for the industrial and commercial
uses of the people, as well as that
| route maps for airplanes may be ac-
curately and expeditiously construct
| ed Col Jones says that with only
slight increase of the engineering per
sonnet the fundamental control sys-
| TENS of the country could be com
pleted within 10 years. After the
work Is once finished 1t will never
| have TO he done again. The accuracy
| Of the system OF eeodetic surveying
used by the survey is so great that
| the needs of all time will be met, and
| il will only occasionally he necessary
to replace a triangulation station or
levelina bench mark when old ones
have been destroyed in some manner.
Remarkable Accuracy.
An accuracy almost uncanny is
| shown in the recently completed sur
vev Of line If levels across South
| Da kota. The line extends from Sioux
| Falls westward to Edgemont, S. OAK.
and forms a loop with another line
| about IS miles south, running from
| F,dgemont back to Sioux Falls. The
circuit is 1895 miles long and the
/ closing error Of the circuit. or the
| difference between the elevation Of
| the bench mark from which work
was started and the elevation of the
same bench mark computed through
the leveling. was only about one
| one.thousa ndth Of an inch per mile.
The Coast and Geodetic Surveys av-
erage closing errors Of circuits of this
kind is about six one.thousandths of
an inch per mile.
In their work of surveying the
coasts the engineers take many
chances which would not be permit
| ted the usual sea captain. 1t Is their
business to sail uncharted waters.
noting dangers that might Turk in
wait for the unsuspecting vessel. They
are the ones who dragged the Alaskan
1 wa tiers. so that pinnacle rocks might
he avoided by the merchant vessels.
A Year Without Wreck.
1t is said that formerly one OF the
principal ways of designating such
rocks was by naming them after YES
| sells which had been wrecked upon
them. That certain number OF YES
| sells would he so wrecked each year
| was taken much as a matter OF course
among those living In Alaska. After
the Coast and Geodetic Survey had
wire-dragged the area conditions I'M