Geometrical instruments – Straight-line light ray type – Level
Reexamination Certificate
2001-10-11
2004-02-10
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Straight-line light ray type
Level
C033S394000, C033S758000, C033S759000, C033S760000, C033S768000, C033S770000
Reexamination Certificate
active
06688010
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a system for determining the height of a tripod-mounted geodetic tool above a reference area-to a spacer and a distance measuring device for such a system.
2. Description of the Related Art
For surveying tasks using geodetic tools, it is necessary to know, for example, the height of the optical axis of the tool above a reference area. The reference area is defined by a geodetic point of reference (reference point) which is marked, for example in a boundary stone.
In DE 40 07 245 A1, a laser apparatus mounted on a tribrach prior to assembly and intended for perpendicular positioning above the reference point is used. The height of the device above the reference point is then to be determined using the laser. Reference points are, for example, generally marked in a boundary stone by indentations or notches. The reference plane is however defined by the maximum projection of the boundary stone. The measurement by means of a laser beam is therefore inaccurate.
Other systems use measuring tapes in the form of roll-type tape measures. The roll-type tape measure is fastened to an adapter (height measuring bracket, height hook) so that it is present in the plumb line above the reference point during the measurement. Known adapters are fastened by means of a spindle in a centering bush of the tool and run around the tripod and the tripod head into the plumb line. An operator pulls the tape measure out of the roll-type tape measure and runs it to the boundary stone. The height of the tool is indicated on a mark on the roll-type tape measure. The measuring procedure is difficult and susceptible to inaccuracies because, on the one hand, the end of the roll-type tape measure has to be held by the user on the boundary stone and, on the other hand, the mark has to be read at a height. Wind-related inaccuracies may also occur. Such adapters consist of metal and are relatively bulky. This make them problematic to transport.
U.S. Pat. No. 5,720,106 describes a measurement of the slope height of a tripod-mounted geodetic tool above the reference area outside the plumb line. Here, however, it is the uncorrected slope height that is indicated on the mark to be read on the roll-type tape measure. The true height of the geodetic tool above the reference area can be calculated based on the slope height and the on the geometrical relationships of the tripod-mounted geodetic tool.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a system of the type stated at the outset for determining the height of a tripod-mounted geodetic tool above a reference area, which system gives sufficiently accurate measurement using simple means.
The arrangement, according to the invention, departs from the principle of measuring inside the plumb line. Instead, the measuring distance makes an angle with the plumb line. By a suitable design of the scale, the perpendicular height above the reference point can nevertheless be read with sufficient accuracy.
On the one hand, a roll-type tape measure which is fastened to a spacer attached to the tribrach or to the instrument, drawn downward and placed against the reference area relative to the point of reference is suitable for the length measurement. The scale on the graduated tape of the roll-type tape measure is adapted and shows not, for example, the length of the measured distance but directly the required perpendicular height of the tool above the point of reference. Alternatively, it is possible to use a measuring stick, for example a plumb bar, which is placed on the reference area in the vicinity of the reference point and is to be read at the spacer. The scale mounted on the plumb bar in turn indicates the perpendicular height. The spacer has relatively small external dimensions compared with known adapters, while roll-type tape measure and plumb bar are in any case carried by the user of the geodetic tool in the standard equipment.
The scale of the roll-type tape measure or plumb bar has nonlinear divisions and—provided that the spacer is aligned horizontally—is calculated using Pythagoras' law, which relates the lengths of the sides of a right-angled triangle to one another. The catheti of the right-angled triangle are formed by the distance from the point of engagement or end of the spacer to the plumb line and the height of this spacer plane above the reference area at the reference point along the plumb line. The hypotenuse of the right-angled triangle is given by the distance between the reference area at the reference point and the end of the spacer. If it is not intended to arrange the spacer horizontally on the tool, the scale of the measuring device coordinated with the spacer, whether roll-type tape measure or plumb bar, is calculated in a correspondingly different manner. What is advantageous is that it is not necessary for the measuring spindle, the measuring blade or a stop of the roll-type tape measure or an end of the plumb bar to be placed directly on the reference point on which the plumb line stands, but can be positioned slightly outside. The resulting inaccuracy of the measurement can be neglected. Rather, the roll-type tape measure or the plumb bar can now be placed on the highest point of the reference point, for example of the boundary stone which defines the reference plane.
If, for example, a roll-type tape measure which is also to be used for measuring lengths other than the height of the tool is now used for measuring the length, application of the nonlinear scale in coded form is then possible—in order to avoid uncertainties in reading. This is also true for the use of an inch rule.
In the context of the present invention, “coded representation” of a scale is intended to mean representations which can be read not directly but only indirectly, whether, for example, by interspersing a mirror (in which case the scale representation is mounted as a mirror image on the scale support), whether via special color filter (in which case the scale representation is in false colors and cannot be differentiated with the naked eye) or whether by interspersing an anamorphotic lens (in which case the scale is mounted with distortion and defocusing). The above examples for coded representation are not definitive. Thus, for example, the provision of reading slides or windows with staggered grid is possible which permits reading of the scale only in cooperation with an opposite grid making it difficult or impossible to read the scale on the scale support directly.
If, for example, a scale is mounted on the scale support in the coded form described above, it can be read only using the corresponding reading means. If the operator attempts to read this coded scale at the reading mark which is coordinated with the scale mounted in uncoded form, the error will be directly evident. Reading is difficult if not impossible. In a corresponding manner, a reading error is avoided for the scale mounted in uncoded form if the operator attempts to read this scale using the reading means.
With the use of a cylindrical lens whose axis runs along the scale support, a compressed scale which is readable only by means of the cylindrical lens can be mounted—preferably in the middle of the scale support. Above and below the compressed scale, which is visible to the naked eye only as a dotted line, in each case directly readable and optionally further, only indirectly readable scales can be mounted. The compressed scale can in this case simultaneously serve as a separating line for different scales above and below it.
Since in general only a relatively small scale region can be read using the reading means, measures are taken to ensure reading which is as error-free as possible. This is achieved, for example, by specially designed scales and/or the magnification of the reading region.
Thus, the scale can be modified in such a way that, even in a relatively small reading region, it is clearly visible in which direction of the scale the numbers are arranged in ascending order.
The
Fulton Christopher W.
Gonzalez Madeline
Leica Geosystems AG
Rothwell Figg Ernst & Manbeck P.C.
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