An Earthworks Calculation System

A large amount of power is needed to shift dirt quickly

Introduction

Compute-a-Grade is an earthworks calculation system for surveyors, designers, earthmoving contactors and farmers. It enables raw staff levels to be entered into the computer direct from the surveyor's field notebook. These levels are related, reduced and saved in a form that can subsequently be used for landform design and all its associated earthworks such as channels, drains, banks, and pads. Reduced levels can also be typed in and saved for later use.

Landform design can be performed on a field of any shape and slopes can be specified along the peg lines or at an angle to them. Grades of best fit can be calculated so as to give the designer an idea of the "cheapest" slope. Grades can be specified or the grades of best fit can be used when calculating volumes of earth to be moved.

History

Compute-a-Grade is the oldest existing landforming program in Australia. The first version of it was written in Basic, in 1979, for a Tandy TRS80 model 1 with 4K of memory. It had no printer and audio tape cassettes were the only storage medium. Although crude by today's standards, it was eagerly accepted by professionals in the field such as Frank Rennick.

The program has been continuously developed since then. The aim has been that it should be friendly to use and that it must meet the requirements of the people using it. The developer has always worked closely with the users.

In 1986 Compute-a-Grade was completely rewritten in "c". The program is still a DOS program but work has been in progress for some time on a Windows version that hopefully will be released soon.

Hardware

The DOS version requires very minimal PC hardware. It will run quite happily on a 486DX or even less if a floating point co-processor is present.

The Windows version will be much more fussy in its minimum requirements - a Pentium II with 32M of memory, a spare 100M of hard disk space and a video card and monitor capable of displaying 1024 x 768 pixels.

Level

This is the surveyor's module of Compute-a-Grade. Staff levels can be entered in any order within a set-up. The different instrument set-ups are related using a foresight and backsight or by entering an instrument height directly. Finally all levels from the field are reduced and saved as a reduced level (RL) file. The main features of Level are:-

• Metric or Imperial measure can be used.
• All Survey points are given grid co-ordinates.
• Input can be changed later if mistakes are found.
• Up to three foresights in each set-up.
• The benchmark can be picked up in any set-up.
• Levels can be entered in metres or centimetres (feet or hundredths of a foot).
• Position of the staff man is shown on the screen when levels are being entered.
• The related and reduced level is displayed as soon as the staff reading is entered.

Field

• Paddocks can be any shape (up to 17 corners).
• Paddocks can be broken up into sections of any shape by specifying the co-ordinates of the corners.
• Fractional (decimal) co-ordinates may be used in specifying corners so that the edge of the designed area is correct.
• Earthworks calculations are always performed within the actual area, not to the nearest peg as in other programs.
• The Grid may be square or rectangular.
• The Grade of best fit is calculated.
• The design grade may be specified along the peg lines or at an angle to them.
• The cut/fill ratio may be set. All calculations will then be performed at this ratio until the ratio is changed.
• The field may be set at a fixed height at a point.
• Volumes of borrow or spread may be included in the calculations.
• The average haul length can be calculated.
• Printouts include a Summary of calculations, a map of natural surface levels, a full map and a cut fill sheet.
• Top-soiling calculations can be incorporated to give top-soiling volumes.

Ditch

• Each point is given an identifying number.
• The distance between points can vary within a line.
• The line of levels can be broken up into sections. Each section can be designed separately.
• The grade of best fit can be calculated.
• Different gradients can be used for bed and bank of a channel.
• A compaction factor can be specified.
• Inside and outside batters can be different.
• The program can balance cut and fill in the works if required.
• Drains can be banked and padded through low spots if required.
• A composite function allows the design of road (bank) beside a channel or some other combination of works.

Hydro

Hydro was added to Compute-a-Grade in the early 90's. It is used for calculating the flow in channels, drains and pipes. It can also calculate the head loss through a fully submerged check. Data for M1 and M2 longitudinal profiles of channels and drains may also be produced.

Interface to other Programs

Compute-a-Grade contains a number of conversions for inputting RL files from other landforming programs. It can also convert from some XYZ formats provided the data is on a grid. This gives a roundabout way of getting GPS data into the program.

Acknowledgements

CAG Software would like to acknowledge the contribution and encouragement given by the following during the continuing development of Compute-a-Grade.

Stan Archard of Archard's Irrigation Pty. Ltd.

Bill Booth of Booth Associates

John Edwards of Goulburn Valley Irrigation Services Pty. Ltd.

Steve England of S. & R. Computer Services.

Michael McBurnie of Michael McBurnie Irrigation Designs.

Frank Rennick of Frank Rennick and Company Pty. Limited.