Surveyor device

This invention is a method for remotely obtaining roadway crown point elevation and horizontal location based on projecting a horizontal laser beam configured vertically in either a continuous or discrete manner across the roadway surface at a predetermined elevation substantially coincident with the crown point of the roadway. The highest elevation of the roadway partially occludes the vertically configured laser beam. The lowest elevation of the laser beam which contacts an array of vertically configured laser receivers positioned on the opposite side of the roadway is by necessity the elevation of the roadway crown. By using an optical detector at a known vertical offset from the laser beam emitter, the angle and hence the distance can be determined to the furthest laser impact with the roadway. This distance information can be combined with the known line between the laser emitter and laser receivers to resolve the horizontal coordinates of that point. In the case where the roadway is found in transition from normal straight roadway to curved roadway, the present method may be modified to calculate the slope of individual segments of the roadway on either side of a break point in order to determine the horizontal location of the break point. The laser apparatus and related components may be integrated into a total station package for automated calculation and derivation of data for input into a data collector.

FIELD OF INVENTION 
This invention relates to surveying instruments and more particularly to a 
surveying device utilizing a laser to accurately define roadway elevations 
remotely. 
BACKGROUND OF INVENTION 
When determining paving quantities, resurfacing grades, side-road tie-in 
grades, or making other design decisions, roadway design engineers must 
know the elevations of the roadway at three important locations of the 
roadway profile. These are the left edge of the pavement, the crown point, 
and the right edge of the pavement. 
Presently, the most economical way for surveyors to gather this information 
is by using a total station package in which a device including a 
theodolite, an electronic distance meter and an electronic data collector 
is fixed over a known ground control point. The horizontal coordinates and 
elevation of the desired points on the roadway profile are determined by 
sighting light reflecting prisms which are positioned at the top of poles 
of controlled heights. Using this conventional scheme, a high level of 
accuracy may be achieved relatively quickly and efficiently in obtaining 
the necessary data. 
However, as traffic volumes increase due to population growth and related 
factors, it is becoming more difficult and hazardous for surveyors to 
access elevation measurements in the middle of the roadway. In some cases 
injury to the surveyor or vehicle occupant results. In some instances time 
consuming roadway closures are the result. In other cases, the design 
engineer may be forced to complete the project without the benefit of 
crown point elevations at all. 
Concise Explanation of Prior Art 
U.S. Pat. No. 5,189,484 to Eric C. Koschmann discloses a laser beam 
detector system utilized to define an elevation or grade. 
U.S. Pat. No. 3,659,949 to Robert R. Walsh, et al. discloses a laser beam 
system for detecting and measuring perametric deviations between surfaces 
including laser targets on opposite sides of a roadway. 
U.S. Pat. No. 5,141,307 to Michael L. Bennett discloses a surveying method 
using a laser-type surveying method for measuring roadway surfaces. 
U.S. Pat. No. 3,846,026 to Kenneth H. Waters discloses a surveying method 
and apparatus for determining various parameters utilizing projected 
energy beams. 
U.S. Pat. No. 4,695,163 to Ronald A. Schachar discloses a method and 
apparatus for determining the shape of an object utilizing a laser light 
source. 
U.S. Pat. No. 4,214,373 to William R. Vessey discloses a grade checker for 
determining the elevation of a grade relative to a pair of reference 
points on opposite sides of the grade. 
Finally, U.S. Pat. No. 4,490,919 to Wieland Feist is considered of general 
interest in that it relates to an arrangement for measuring the elevations 
of terrain points. 
BRIEF DESCRIPTION OF INVENTION 
After much research and study into the above mentioned problems, the 
present invention has been developed to provide a method for remotely 
obtaining roadway crown point elevation and horizontal location based on 
projecting a horizontal laser beam configured vertically in either a 
continuous or discrete fashion across the roadway surface. The highest 
elevation of the roadway partially occludes the vertically configured 
laser beam. The lowest elevation of the laser beam which reaches the laser 
receiver positioned on the opposite side of the roadway is by necessity 
the highest elevation of the roadway crown. 
By using optical detector equipment at a known vertical offset from the 
laser beam emitter, the angle and hence the distance can be determined to 
the furthest laser impact with the roadway. This distance information can 
be combined with the known line between the laser emitter and laser 
receivers to resolve the horizontal coordinates of that point. 
In the case where the high edge of pavement elevation is higher than the 
cross-slope break point formed continuously from the crown, by utilizing 
strobing or some other method for giving a unique identity to each 
discrete beam in the vertically configured laser, the elevation and offset 
of the cross-slope break point can be determined by measuring angles from 
optical detector equipment at a known vertical offset from the laser beam 
emitter. 
In the case where the high edge of pavement elevation is higher than the 
cross-slope break point usually formed continuously from the crown, by 
deliberately varying the angle at which the lowest beam is emitted until 
it is occluded by that break point, the lowest elevation at which the beam 
reaches the laser receivers can be used to determine the elevation of the 
break point. Results from the measurements can be relayed to a data 
collector via voice communication or by telemetry carried over laser or 
radio transmission. 
The laser emitter apparatus and the related components described herein may 
be integrated into a total station package for automated calculation and 
derivation of data for input into the data collector. 
In view of the above, it is an object of the present invention to provide 
the means to remotely determine the elevation and horizontal position of 
the crown point of a roadway surface without endangering the surveyor or 
the traveling public and without impeding normal traffic flow. 
Another object of the present invention is to provide roadway design 
engineers and surveyors with a highly accurate means of determining 
critical locations of the roadway cross-section. 
Another object of the present invention is to provide a laser apparatus 
that can be integrated into existing total station arrangements with 
relatively minor modifications to that existing equipment, thereby 
providing a cost effective means of retrofitting existing total station 
packages already in use. 
Another object of the present invention is to provide a laser apparatus 
wherein survey measurements can be relayed to a data collector via voice 
communication or by telemetry carried over laser or radio transmission. 
Another object of the present invention is to provide a relatively simple 
laser apparatus wherein employee training for correct implementation will 
be minimal and that trouble shooting by field personnel is greatly 
facilitated. 
Another object of the present invention is to provide a laser apparatus 
wherein the components are relatively simple and light weight and thus 
inventories of replacement parts may be conveniently maintained. 
Another object of the present invention is to provide a laser surveying 
apparatus which incorporates snap-and-go design features for attachment 
and integration of the various components. 
Other objects and advantages of the present invention will become apparent 
and obvious from a study of the following description and the accompanying 
drawings which are merely illustrative of such invention.

DETAILED DESCRIPTION OF INVENTION 
With further reference to the drawings, a laser apparatus for remotely 
determining roadway crown elevation in accordance with the present 
invention is illustrated in FIG. 1, and indicated generally at 10. A laser 
beam emitter 11 is positioned on one edge of a roadway, indicated 
generally at 12, which is depicted in cross-sectional profile in FIG. 1. 
Roadway 12 includes a crown point 13 which is of a higher elevation than 
either the left edge of pavement 14 or the right edge of pavement 15. 
In the preferred embodiment of the present invention, laser light beams 16 
projected from laser beam emitter 11 are perfectly horizontal and directed 
toward laser receivers 17, which are positioned directly across roadway 12 
from laser beam emitter 11. 
Because there is a point on roadway 12 higher in elevation than the lowest 
level of laser emitter 11, some of the vertically configured laser beams 
16 are blocked by roadway 12. Laser receivers 17 detect all of the laser 
beam 16 that passes above crown point 13 having circuitry to detect which 
of these laser beams 16 is the lowest elevation. The distance from the low 
point of detector 17 to the low point of laser light beam 16 may be 
calculated and designated as length Z 18 as indicated in FIG. 1. 
Further, if the elevation of the low point of laser receivers 17 is known, 
the value of length Z 18 may be added to it to determine the elevation of 
crown point 13 of roadway 12. It will be appreciated that the horizontal 
distance designated as length X 23 from the edge of pavement to crown 
point 13 can not be determined from this method. 
Since the elevation of the left edge of pavement 14 and the right edge of 
pavement 15 will usually be different from each other, the value of length 
Z 18 between the crown 13 and the left edge of pavement 14, as depicted in 
FIG. 1, and the value of length Z 18 between the crown 13 and the right 
edge of pavement 15 will be different. It will be appreciated that the 
laser apparatus 10 as depicted in FIG. 1 may be set up in reverse to 
address this situation. 
In the preferred embodiment of this system, laser beam emitter 11 and laser 
receivers 17 are attached to an end of prism poles 19. The manufacturer 
would ensure that laser light beams 16 would be projected from laser 
emitter 11 perpendicular to prism poles 19 within specified tolerances. 
This will insure that a plumb prism pole 19 will result in a horizontal 
beam 16. 
In practical use of the device in the field, it is anticipated that the 
laser apparatus 10 of the present invention will hover near perfect 
horizontal position, but only pass through the horizontal tolerance limits 
briefly because the prism pole 19 is typically hand held by the surveyor. 
In order to insure an accurate reading, the laser receiver 17 is provided 
with an elevation lock (not shown) that detects when the incoming laser 
beams 16 are horizontal and records length Z 18 only at those instances. 
This elevation lock function may be accomplished by enabling the laser 
receiver 17 to compare the elevation of origin of any laser beam 16 from 
the laser emitter 11 to the elevation at which the laser beam 16 strikes 
the laser receiver 17. The data corresponding to the elevations of the 
laser emitter 11 and laser receiver 17 are communicated to the laser 
receiver 17 in order for the elevation lock to accept readings as 
accurate. 
Further, an automatic leveling sensor (not shown) may be integrated into 
the laser emitter 11 to disable laser beam 16 transmission until the laser 
emitter 11 is within tolerance of horizontal. By insuring that the laser 
beams 16 are transmitted only when horizontal, the accuracy of the reading 
may be controlled. 
As illustrated in FIG. 2, prism poles 19 may have mounted thereon at an 
opposite end an optical detector 20, which functions to determine the 
points at which laser illumination is observed on roadway 12. Further, 
with prism pole 19 being held vertical with the aid of a leveling bubble 
21, or a leveling sensor (not shown), optical detector 20 determines the 
angle B 22 at which the laser illumination is observed. 
Thus it will be appreciated that the horizontal position of crown point 13, 
designated as length X 23, may now be accurately determined using the 
laser apparatus of the present invention as shown in FIG. 2. The far side 
12a of the crown roadway 12 is in the shadow of laser beam emitter 11 and 
is not illuminated by it. The near side 12b of roadway 12 is struck by the 
laser beams 16 which are blocked by roadway 12. It will be appreciated 
that crown point 13 is the point of roadway 12 furthest from laser beam 
emitter 11 that is illuminated by laser beams 16. 
With prism pole 19 being held vertical or plumb with the aid of leveling 
bubble 21, or a leveling sensor (not shown) optical detector 20 determines 
the angle B 22 at which laser illumination is observed. 
The vertical height h 24 of optical detector 20 above laser emitter 11 is a 
known distance. With the value of length Z 18 having been previously 
determined by the method described in FIG. 1, and with height h 24 known, 
the value h 24 minus Z 28 can be calculated. Then, the position of crown 
point 13 designated by horizontal length X 23 can be computed using 
trigonometry. 
The value of horizontal length X 23 is actually an intermediate value 
necessary to calculate the relative horizontal position (Northing and 
Easting) of the crown point 13, in accordance with standard surveying 
methods. 
Referring now to FIG. 3, with horizontal length X 23 known from the 
procedure in FIG. 2, the angle A 25 of the laser beams 16 in relation to 
North on the survey map can be computed from the previously known 
coordinates of laser emitter 11 and laser receivers 17 using trigonometry. 
Thus, with length X 23 and angle A 25 now known, the relative horizontal 
position, designated by value E 26 and value N 27 in relation to any grid 
reference including true North, can be computed and added to the database. 
Directional indicator, indicated generally at 39, is shown in FIG. 3 for 
reference. 
The above methods describe procedures for determining elevation and 
horizontal position only for the case where there is a crown point 13 in 
the roadway 12 higher than both edges of pavement. 
Approximately 2% to 10% of the typical roadway is found in the transition 
from straight roadway to curved roadway. During this transition, as shown 
in FIG. 4, one edge of pavement is higher than the break point 29, 
previously designated crown point 13 in the straight roadway case. 
However, in contrast to the straight roadway example, the slope from one 
edge of pavement to the break point 29 is not the same as the slope from 
the break point 29 to the other edge of pavement as illustrated in FIG. 4. 
As will be appreciated by referring to FIG. 4, laser receivers 17 on the 
left edge of pavement 14 are at a higher elevation than break point 29 of 
the roadway 12, but the slope from the left edge of pavement 14 to break 
point 29 is at a different rate than the slope from the break point 29 to 
the right edge of pavement 15. 
The method shown in FIG. 4 uses discrete identifiable laser beams 16 at 
known elevations and an optical detector 20 at a known vertical height 
above laser beam emitter 11 to determine the slope of the pavement on 
either side of break point 29. To insure an accurate reading the laser 
beams 16 must be horizontal, the prism pole 19 supporting the optical 
detector 20 must be vertical, and the optical detector 20 must be plumb. 
The slope on either side of break point 29 is determined by the method 
hereinafter described. 
Two discrete identifiable laser beams 16 are projected onto roadway 12 with 
a known difference in elevation, designated as length L' 30. Using the 
method described for FIG. 2, length X' 31 is computed using optical 
detector 20 to measure the angle B 22 and using the related length Z' 34 
for this segment of roadway 12. These data are then used to calculate the 
slope on that segment of roadway 12 corresponding to length X' 31. 
Similarly, two different identifiable laser beams 16 are projected onto 
roadway 12 with a known difference in elevation designated as length L" 
32. Again, the method of FIG. 2 is utilized to compute length X" 33 by 
using optical detector 20 to measure the angle B 22 and the related length 
Z" 35 for this segment of roadway 12 in order to calculate the slope on 
each side of break point 29. From this information and the known locations 
of edges of pavement, the elevation and horizontal location of break point 
29 can be determined. 
An alternative method of determining the break point 29 of the transitional 
roadway described above is illustrated in FIGS. 5 and 6. The method of 
FIGS. 5 and 6 uses laser emitters 11 which can project laser light beams 
16 at varying angles to vertical. As shown in FIGS. 5 and 6, laser beams 
16 are blocked by break point 29 of roadway 12 up to a specific angle C 
36. By deliberately varying angle C 36 at which laser beam 16 is projected 
from laser emitter 11 until it is occluded by break point 29, the lowest 
elevation at which laser beam 16 reaches laser receiver 17 can be used to 
derive the elevation of break point 29. 
The relative elevation Z"' 37 of the origin of laser beams 16 and the 
relative elevation Z"" 38 at the location where laser beams 16 strike 
laser receivers 17 can be utilized with the coordinates of the edges of 
the pavement to compute a line along which break point 29 will lie. 
As shown in FIG. 6 another laser emitter 11 projecting from the opposite 
side of roadway 12 to another array of laser receivers 17, using the same 
procedure can determine another line along which break point 29 lies. 
These two lines can then be used to calculate the horizontal and vertical 
coordinates of break point 29 as illustrated in FIG. 7. 
In the case of a fully elevated curved roadway where one edge of pavement 
is higher than the other edge there is a single, continuous slope from one 
edge of pavement to the other, the elevation at the mid-point of the 
roadway can be calculated by using the known slope from one edge of the 
pavement to the other. In this instance, no special laser apparatus is 
required. 
From the above it can be seen that the present invention provides the means 
to remotely determine the elevation and horizontal position of the crown 
point of the roadway without endangering the surveyor or impeding normal 
traffic. 
Further, the present invention may be adapted to accurately measure 
straight and transitional roadway surfaces and it can be integrated into 
existing total station packages and/or Global Positioning Systems (GPS) 
with relatively minor modifications to that equipment. Thus, the system of 
the present invention may be retrofitted to total survey stations already 
in use and sold at a price comparable to other elements of a total station 
package. 
Finally, since the inventive concept is relatively simple, employee 
training will be minimal and trouble shooting of problems by field 
personnel is greatly facilitated. 
The present invention may, of course, be carried out in other specific ways 
than those herein set forth without departing from the spirit and 
essential characteristics of such invention. The present embodiments are, 
therefore, to be considered in all respects as illustrative and not 
restrictive, and all changes coming within the meaning and equivalency 
range of the appended claims are intended to be embraced therein.