A time–distance diagram is generally a diagram with one axis representing time and the other axis distance. Such charts are used in the aviation industry to plot flights,[1] or in scientific research to present effects in respect to distance over time. Transport schedules in graphical form are also called time–distance diagrams,[2] they represent the location of a given vehicle (train, bus) along the transport route.[3]
In project management, a time–distance diagram (also called time-chainage diagram, time–distance chart, time-chainage chart, time–location diagram, time-location chart, March chart, location–time chart, orthogonal diagram, line of balance chart,[4] linear schedule or horse blanket diagram[5]), is a method of graphically presenting a time schedule for all types of longitudinal projects such as pipeline, rail, bridge, tunnel, road, and transmission line construction.
Activities in time–distance diagrams are displayed both along a time axis and along a distance axis according to their relative linear position. This allows showing not only the location of the activity but also the direction of progress and the progress rate. Activities can be presented as geometrical shapes showing the occupation of the work site over time such that conflicting access can be detected visually. Different types of activities are differentiated by color, fill pattern, line type, or special symbols. A symbolic drawing along the distance axis is often used to improve the understanding of the time–distance diagram.
The advantage of a time–distance diagram is that it nicely shows all visible activities along the construction site on a single diagram.
A time–distance diagram is a chart with two axes: one for time, the other for location. The units on either axis depend on the type of project: time can be expressed in minutes (for overnight construction of railroad modification projects such as the installation of switches) or years (for large construction projects); the location can be (kilo)meters, or other distinct units (such as stories of a high-rise building).
Normally, the time axis is drawn vertically from top (start of project) to bottom (end of project), and the location axis is drawn horizontally. The direction of the chainage is usually chosen with consideration of geographical position of the project, with the numbers either increasing or decreasing. The location axis is often enhanced with a schematic of the construction project. Other, location-specific information (aerial photos, cross-sectional views) can be added to enhance the visualization of the work site.
A legend explaining the meaning of the various colors, symbols and line types used in the chart may be included in the time–distance diagram. Other information shown may be cost and resource histograms along the time axis.
The drawing area may contain grid lines to ease comprehension of the chart: hours, days, weeks, months, years, for the time axis; equidistant units along the distance axis or specific locations (piles, stations, foundations, etc.). The background of the drawing area may be enhanced with time and location related information such as close seasons, hold-off intervals, meteorological data (rain/snow fall, temperatures).
The project activities are placed within the drawing area according to their specific nature:
Annotations such as boxed text and activity labels within the drawing area improve the level of information.
Time–distance diagrams can be created using any kind of drawing tool, certainly one which allows scaled drawing (for example, CAD editors, Visio). Sometimes, spreadsheet tools are employed where the width of the columns and the height of the rows form the distance and time scales.
However, in real project life, a time schedule needs to be adjusted continuously: This is when the use of specialized tools quickly brings out their advantage. These tools (see External links below) are project management tools in their own right with an emphasis on the ability to present the time schedule as time–distance diagram. Activities can be edited using project management terminology plus all drawing attributes for the activity's shape. Special features allow dependency links (with lags), complex scaling, access conflict detection, resource-dependent progress, and more. Most often, such tools provide various interfaces to other project management software, at least to import and export activity information. Complex systems (such as TimeChainage, DynaRoad, TILOS or Time Location Plus) even integrate into commonly used project management software (Primavera, Microsoft Project, Asta Powerproject).
Linear Project Software Pty Ltd, Australia
from projects using time-distance diagrams)