Download - brief description on highway engineering
ITEM 1: INTRODUCTION
SELECTING THE LOCATION
OF A PROPOSED
HIGHWAY IS AN
IMPORTANT INITIAL
STEP IN ITS DESIGN.
THE DECISION TO
SELECT A PARTICULAR
LOCATION IS USUALLY
BASED ON
TOPOGRAPHY, SOIL
CHARACTERISTICS, ENVIRONMENTAL FACTORS SUCH AS
NOISE AND AIR POLLUTION, AND ECONOMIC FACTORS.
THE DATA REQUIRED FOR THE DECISION PROCESS ARE
USUALLY OBTAINED
FROM DIFFERENT
TYPES OF SURVEYS,
DEPENDING ON THE
FACTORS BEING
CONSIDERED. MOST
ENGINEERING
CONSULTANTS AND
STATE AGENCIES PRESENTLY INVOLVED IN HIGHWAY
LOCATIONS USE COMPUTERIZED TECHNIQUES TO
PROCESS THE VAST AMOUNTS OF DATA THAT ARE
GENERALLY HANDLED IN THE DECISION PROCESS. THESE
TECHNIQUES INCLUDE REMOTE SENSING, WHICH USES
AERIAL PHOTGRAPHS FOR THE PREPARATION OF MAPS,
AND COMUTER GRAPHICS, A COMPUTER MONITOR. IN
THIS REPORT, WE PRESENT A BRIEF DESCRIPTION OF THE
CURRENT TECHNIQUES USED IN HIGHWAY SURVEYS TO
COLLECT AND ANALYZE THE REQUIRED DATA, AND THE
STEPS INVOLVED IN THE PROCEDURE FOR LOCATING
HIGHWAYS. WE ALSO COVER EARTHWORK
COMPUTATIONS AND MASS DIGRAMS, SINCE AN
ESTIMATE OF THE AMOUNT OF THE EARTHWORK
ASSOCIATED WITH ANY GIVEN LOCATION IS REQUIRED
FOR ECONOMIC EVALUATION OF THE HIGHWAY AT THAT
LOCATION. THE RESULT OF THE ECONOMIC EVALUATION
AIDS IN THE DECISION TO ACCEPT OR REJECT THAT
LOCATION.
ITEM 2: HIGHWAY SURVEY METHODS
HIGHWAY SURVEYS USUALLY
INVOLVE MEASURING AND
COMPUTING HORIZONTAL
AND VERTICAL ANGLES,
VERTICAL HEIGHTS
(ELEVATIONS) AND
HORIZONTAL DISTANCES.
ITEM 3: GROUND SURVEYS
GROUND SURVEYS ARE THE BASIC LOCATION
TECHNIQUES FOR
HIGHWAYS. THE TOTAL
STATION IS USED OF
MEASURING ANGLES IN
BOTH VERTICAL AND
HORIZONTAL PLANES,
DISTANCES AND CHANGES
IN ELEVATION.
ITEM 5: TOTAL STATION
A TOTAL STATION IS BOTH AN ELECTRI-THEODOLITE AND
ELECTRONIC DISTANCE-MEASURING DEVICE (EDM).
ITEM 5a: ELECTRIC DISTANCE MEASURING DEVICES (EDM)
AN EDM DEVICE CONSISCTS MAINLY OF A TRANSMITTER
LOCATED AT ONE END OF THE
DISCANCE TO BE MEASURED AND A
REFLECTOR AT THE OTHER END. IT IS
DETERMINES THE DISTANCES UP TO
1,000 METERS IN AVERAGE
ATMOSPHERIC CONDITIONS.
ITEM 6: MEASUREMENT OF HORIZONTAL ANGLES
A HORIZONTAL ANGLE CAN BE
MEASURED BY SETTING THE
THEODOLITE OR TOTAL STATION
DIRECTLY OVER THE POINT O. WHEN
USING A TOTAL STATION, THE ANGLE
MEASURED IS SHOWN IN A DIGITAL
READOUT WHEN A HORIZONTAL READ OUT IS SELECTED.
ITEM 7: MEASUREMENT OF VERTICAL ANGLES
THE THEODOLITE MEASURES VERTICAL ANDLES BY USING
THE FIXED VERTICAL GRADUATED ARC OR VERNIER AND
A SPIRIT LEVEL ATTACHED TO THE TELESCOPE. WHEN
USING TOTAL STATION, THE ANGLE
MEASURED IS SHOWN IN A DIGITAL
READOUT WHEN A VERTICAL
READOUT IS SELECTED.
ITEM 8: DUMPTY LEVEL
THE ESSENTIAL PARTS OF A
LEVEL ARE THE TELESCOPE WITH
VERTICAL AND HORIZONTAL
CROSS HAIRS, A LEVEL BAR, A
SPINDLE, AND A LEVELING HEAD.
THE LEVER BAR ON WHICH THE
TELESCOPE IS MOUNTED IS RIGIDLY FIXED TO THIS
SPINDLE.
ITEM 9: SURVEY DATA COLLECTOR
SURVEY DATA COLLECTORS ARE
DEVICES THAT CONNECT TO ANY
SURVEY INSTRUMENT (TOTAL
STATION) THROUGH A CABLE OR
BLUETOOTH THAT ALLOWS A SURVEYOR TO SECURE
INSTRUMENT'S RAW DATA STRING INTO COORDINATES
AND ELEVATION.
ITEM 10: MULTILAYERED INFORMATION
WITH THE DIGITAL AGE, MANY
PROJECTS ARE SUBMITTED IN
DIGITAL FORMAT LIKE COMPUTER
AIDED DESIGN DRAFTING, OR CADD
USING PROGRAMS SUCH AS
AUTOCAD.
ITEM 11: GLOBAL POSITIONING SYSTEM SURVEYS
THE GLOBAL POSITIONING SYSTEM (GPS) IS A SATELLITE-
BASED SYSTEM THAT USES A CONSTELATION OF 28
SATELLITES TO GIVE A USER AN ACCURATE POSITION.
GPS SURVEYING IS AN EVOLVING PERFORMING TYPES OF
GPS SURVEYS RECEIVERS AND
SOFTWARE SHOULD BE SUITABLE FOR
A SPECIFIC SURVEY AS STATED BY THE
MANUFACTURER.
ITEM 12: ANTENNAS
WHENEVER FEASIBLE, ALL
ANTENNAS USED FOR A PROJECT
SHOULD BE IDENTICAL. FOR VERTICAL CONTROL
SURVEYS, IDENTICAL ANTENNAS ARE USED UNLESS
SOFTWARE IS AVAILABLE TO ACCOMODATE THE USE OF
DIFFERENT ANTENNAS. THE USE OF RANGE POLES
AND/OR STAKE-OUT POLES TO SUPPORT GPS ANTENNAS
ARE ONLY USED FOR THIRD ORDER HORIZONTAL AND
GENERAL-ORDER
.SURVEYS
ITEM 13: REMOTE SENSING
REMOTE SENSING IS THE MEASUREMENT OF DISTANCES
AND ELEVATIONS BY USING DEVICES LOCATED ABOVE
THE EARTH, SUCH AS AIRPLAINES OR ORBITTING
SATELLITES USING GLOBAL POSITIONING SATELLITE
SYSTEM (GPS).
ITEM 14: OBTAINING AND INTERPRETING AERIAL
PHOTOGRAPHS
THE PHOTOGRAPHS ARE TAKEN FROM AIRPLANES WITH
THE AXIS OF THE CAMERA AT A NEAR VERTICAL
POSITION. THE ASIX SHOULD BE EXACTLY VERTICAL BUT
THIS POSITION IS USUALLY DIFFICULT TO OBTAIN DUE TO
THE MOTION OF THE AIRCRAFT.
ITEM 15: PHOTOGRAMMETRY
PHOTOGRAMMETRY IS
THE SCIENCE OF MAKING
MEASUREMENTS FROM
PHOTOGRAPHS,
ESPECIALLY FOR
RECOVERING THE EXACT
POSITIONS OF SURFACE
POINTS. MOREOVER, IT MAY BE USED TO RECOVER THE
MOTION PATHWAYS OF DESIGNATED REFERENCE POINTS.
ITEM 16: FIDUCIAL
MARKS
A FIDUCIAL MARK IS AN
OBJECT PLACED IN THE
FIELD OF VIEW OF AN
IMAGING SYSTEM
WHICH APPEARS IN THE IMAGE PRODUCED, FOR USE AS A
POINT OF REFERENCE OR A MEASURE. IT MAY BE EITHER
SOMETHING PLACED INTO OR ON THE IMAGING SUBJECT,
OR A MARK OR SET OF MARKS IN THE RETICLE OF AN
OPTICAL INSTRUMENT.
ITEM 17: PRINCIPAL POINT
PRINCIPAL POINT IS THE POINT
OF INTERSECTION OF THE
OPTICAL AXIS OF THE AERIAL
CAMERA WITH THE
PHOTOGRAPHIC PLANE. IT IS
ALSO THE INTERSECTION OF THE
LINES JOING OPPOSITE FIDUCIAL
MARKS GIVES THE GEOMETRIC
CENTER OF THE PHOTOGRAPH.
ITEM 18: CONTROL POINTS
CONTROL POINT IS THE PRIMARY/BASE CONTROL USED
FOR PRELIMINARY MEASUREMENTS;
IT MAY CONSIST OF ANY KNOW POINT
CAPABLE OF ESTABLISHING
ACCURATE CONTROL OF DISTANCE
AND DIRECTION.
ITEM 19: AERIAL SURVEY
AERIAL SURVEY IS A METHOD
OF COLLECTING GEOMATICS
OR OTHER IMAGERY BY
USING AEROPLANES,
HELICOPTERS, UAVS,
BALLOONS AND OTHER
AERIAL METHODS.
ITEM 20: STEREOSCOPES
STEREOSCOPES IS THE INSTRUMENT THAT CONVERTS
THE AERIAL PHOTOGRAPHS INTO MAPS. IT IS ALSO A
TECHNIQUE FOR CREATING OR ENHANCING THE ILLUSION
OF DEPHT IN AN IMAGE BY
MEANS OF STEREOPSIS FOR
BINOCULAR VISION.
ITEM 21: SCHEMATIC OF A SINGLE AERIAL PHOTOGRAPH
EVEN WHEN THE AXIS OF THE CAMERA IS PERFECTLY
VERTICAL THE SCALE ON THE PHOTOGRAPH VARIES
FROM POINT TO POINT AND DEPENDS ON THE ELEVATION
OF THE POINT AT WHICH THE SCALE IS DETERMINED.
ITEM 22: LIDAR
SCANNING
LIDAR IS A REMOTE SENSING
TECHNOLOGY THAT
MEASURES DISTANCE BY
ILLUMINATIONG A TARGET WITH LASER AND ANALYZING
THE REFLECTED LIGHT.
ITEM23: AIRBORNE LIDAR
AIRBORNE LiDAR IS PERFORMED
FROM AN AIRCRAFT. THE
INSTRUMENT IS ATTACHMENT
ATTACHED TO A FIXED-WING OR
ROTARY-WINGS AIRCARFT AND
THE SCANNER EMITS A LIGHT
LASER BEAM THAT IS REFLECTED FROM A MIRROR AND
DIRECTED AT THE SURFACE OF THE EARTH.
ITEM 25: TERRESTRIAL LIDAR
THE TERRESTRIAL LiDAR SCANNER IS A SPECIFIC,
LOCALIZED FORM OF LiDAR. THE SCANNED IS MOUNTED
ON A TRIPOD OR STATIONARY VEHICLE. A LIGHT PULSE IS
TRANSMITTED AND THE TIME IT TAKES TO RETURN IS
MEASURED PROVIDING THE SOFTWARE OF A
POSITIONING ON THE EARTH.
ITEM 26: SCANNER ADVANTAGES
THE SCANNER IS MOST USEFUL WHEN CONFIDENCE IN
THE DATE IS IMPORTANT, THERE ARE TIME CONSTRAINTS
ON A PROJECT, FAST TURN-AROUND IS NEEDED, OR
WHEN THE AREA IS DIFFICULT OR DANGEROUS TO
ACCESSOR
DANGEROUS TO MEASURE.
ITEM 27: GEOGRAPHIC INFORMATION SYSTEMS
GEOGRAPHIC INFORMATION SYSTEMS (GIS) CAPTURE,
STORE, ANALYZE, AND MANAGE DATA ASSOCIATED
ATTRIBUTES WHICH ARE SPATIALLY REFERENCED TO THE
EARTH. GIS IA A COMPUTER SYSTEM ACCESSING A
DATABASE OF LAYERS OF INFORMATION.
ITEM 28: GPS
SATELLITE SURVEYING AND SATELLITE IMAGERY
SURVEYORS USE GLOBAL POSTIONING
SYSTEMS (GPS) IN ALL KINDS OF SURVEYING. SATELLITE
IMAGERY IS ALSO BEING USED TO MONITOR MOVEMENTS
ON THE EARTH'S SURFACE-EARTH QUAKE ZONES,
POTENTIAL MUD SLIDES OR EVEN TROOPS ON THE MOVE
IN A WAR ZONE.
ITEM 29:
HYDROGRAPHIC SURVEYING
HYDROGRAPHIC SURVEY IS THE SCIENCE OF
MEASUREMENT AND
DESCRIPTION OF FEATURES
WHICH AFFECT MARITIME
NAVIGATION, MARINE
CONSTRUCTION,
DREDGING, OFFSHORE OUL EXPLORATION, DRILLING AND
RELATED ACTIVITIES.
ITEM 30: SUMMARY
THE SELECTION OF A SUITABLE LOCATION FOR A NEW
HIGHWAY REQUIRES INFORMATION OBTAINED FROM
HIGHWAY SURVEYS. THESE SURVEYS CAN BE CARRIED
OUT BY EITHER CONVENTIONAL GROUND METHODS OR
USE OF ELECTRIC EQUIPMENT AND COMPUTERS. A BRIEF
DESCRIPTION OF SOME OF THE MORE COMMONLY USED
METHODS OF SURVEYS HAS BEEN PRESENTED TO
INTRODUCE THE READER TO THESE TECHNIQUES.