PROGRAMS AND PLANS: Latitude-longitude Well Numbers
Minutes, use zeros for seconds of latitude and longitude and
underscore digits for minutes. Example: 354200N1011900.1
Where use of minutes is to allow for later more accurate well
location in the field, digits for seconds of latitude and
longitude should be omitted. Example: 3542_N10119_.1.
Inaccuracies may result either from inadequate field descriptions
of well location or because available maps are too inaccurate or
too small in scale to spot wells precisely. Note that the precise
latitude and longitude coordinates scaled from the map will be
used whenever conditions permit. This is not a system for
rounding numbers but a system for showing the accuracy of the well
locations. Use of latitude and longitude numbers only to minutes
should be kept to a minimum in order that maximum benefits will be
derived from the well-data storage and retrieval system.
Please note that the latitude and longitude coordinates for a well
number will always be the coordinates of the southeast corner of
some quadrangle in which the well is located. Thus, the well will
always be to the north and west of the geographic point designated
by the well number. (See sketch B.)
If a well falls on the line between 2 seconds of latitude or
longitude, the coordinates of the quadrant north or west of the
well should be used for the well number (sketch B).
The scale of available maps for some areas will be too small to
scale well locations to the nearest second. However, as better
maps become available, more and more wells can be located with the
accuracy necessary for accurate plotting and for use of precise
location numbers.
(s) A. H. Lang
for O. M. Hackett
Attachment
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Subject: OGW Technical Memorandum 64.20
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Date: Mon, 16 Dec 1996 08:40:12 -0500
From: "Velvie E Stockdale, Office Automation Assistant, Reston, VA "
UNITED STATES
DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
Washington, D.C. - 20242 February 4, 1964
Code: 4056 0001
GROUND WATER BRANCH MEMORANDUM No. 64.20
To : District Chiefs and Staff Officials
From : Chief, Ground Water Branch
Subject : PROGRAMS AND PLANS: Latitude-longitude Well Numbers
This memorandum contains more specific instructions for
determining well-code numbers. These instructions replace those
in GWB Memorandum 64.10 for use with the 5-year water-level report.
This memorandum also provides background information about the
system that will make it easier to understand and use.
The procedures outlines in this memorandum are to be used after the
well is located in the field and its location spotted on a map.
They in no way imply that a change in field procedure is necessary.
No more than normal care needs to be exercised in locating wells.
Thus, the new system does not change present good field practices.
The well-code number is primarily for the purpose of isolating and
identifying data for discrete points. Each well therefore must
have a unique number. The well-code number serves to locate a point
on a map but it need not be an accurate reflection of the location
of the well on the ground. For example, a well may be known to be
north of another well even though the exact location of the second
is not known. Plotting of relative locations on a map and scaling
of seconds will result in different number for each well even
though the degree of accuracy for each well is not more than 10
seconds or even 1 minute.
As indicated in GWB Memorandum 64.8, the system was designed to be
applicable worldwide. It is expected that computes may plot wells
and well data directly from IBM cards. Computer plotting is
already being done by the petroleum industry and is being used in
oceanographic studies.
The principal problems in determining precise well numbers
are:
1) Most wells are not field located as accurately as
100 feet in a given direction. (100 feet is
approximately 1 second of latitude.)
2) The scale of available maps, in some areas, is too
small to determine seconds of latitude and longitude
precisely for a point on the map. Scaling from a
map to seconds probably will be impossible for maps
of smaller scale than 1:62,500. At 62:500, 1 second
of latitude is about .02 inch.
3) Available maps may contain inconsistencies or inaccuracies
that affect the numbering of seconds, i.e., misplaced
physical features.
To determine the latitude-longitude number for a well, the
following steps are suggested:
1) Spot the well location on a map, preferably a
topographic map at scale 1:62,500 or larger.
Information on the well schedule or field data sheet
should be used with reference to map features to spot
the well as accurately as possible. If information
on the field-data sheet is not accurate, judgment
will have to be used to make the best spotting
possible.
2) Once the well is spotted on a map the coordinates of
that point can be scaled precisely even though the
point may not represent the accurate location of the
well on the ground. (See sketch A, attached).
3) Indicate your judgment of the accuracy of the well
location as follows:
a) Both field location and map spotting are accurate
to nearest second of latitude and longitude:
Use latitude and longitude numbers to seconds.
Example: for well A, sketch B, 354213N1011937.1.
b) Not accurate to nearest seconds but accurate
to better than 10 seconds of latitude and
longitude: Reduced accuracy may result from
inadequate field location but scale and accuracy
of map permits numbers to nearest second.
Latitude and longitude coordinates to the
nearest seconds are used, but 1-second digits
are underscored. Example: 354213N1011937.1.
c) Accurate to nearest 10 seconds of latitude and
longitude: Map scale is too small to number
closer than 10 seconds. Latitude and longitude
coordinates to nearest 10 seconds are used, but
10-second digits are underscored. Example:
354210N1011930.1.
d) Accurate to nearest minute: For well locations
accurate only to nearest minute but map
scales permit numbering to seconds, show seconds
of latitude and longitude but underscore digits
for minutes. Example 354213N1011937.1.
For wells where field locations are accurate
only to the nearest minute the map scales permit
determinations only to minutes, use zeros for
seconds for latitude and longitude and
underscore digits for minutes. Example:
354200N1011900.1.
Where use of minutes is to allow for later
more accurate well location in the field, digits
for seconds of latitude and longitude should
be omitted. Example: 354 N10119 .1.
Inaccuracies may result either from inadequate field
descriptions of well location or because available maps are too
inaccurate or too small in scale to spot wells precisely. Note
that the precise latitude and longitude coordinates scaled from the
map will be used whenever conditions permit. This is not a system
for rounding numbers but a system for showing the accuracy of the
well locations. Use of latitude and longitude numbers only to
minutes should be kept to a minimum in order that maximum benefits
will be derived from the well-data storage and retrieval system.
Please note that the latitude and longitude coordinates for a
well number will always be the coordinates of the southeast corner
of some quadrangle in which the well is located. Thus, the well
will always be to the north and west of the geographic point
designated by the well number. (See sketch B.)
If a well falls on the line between 2 seconds of the latitude
or longitude, the coordinates of the quadrant north or west of the
well should be used for the well number (sketch B).
The scale of the available maps for the same areas will be too
small to scale well locations to the nearest second. However, as
better maps become available, more and more wells can be located
with the accuracy necessary for accurate plotting and for use of
precise location numbers.
Attachment
/s/ O.M. Hackett
WRD Distribution: A, B3, S3, FO3, SL