Measuring Wheels Examined
Recording measurements of long distances can be difficult. Since video surveillance work often requires stepping of distances in the hundreds of feet, a cheap and easy to use method of measuring large areas is desirable. In this update, we examine 'Measuring Wheels' and discuss the advantages and disadvantages of this type of measuring device.
When the wheel travels, an integrated counter keeps track of the exact distance. While very simple, the method is reliable and accurate. Typically, automobile odometers work on the same principal.
Measuring wheels are simple devices composed of just a few major components:
Wheel: The 'business end' of the device. While many designs are avilable, larger diameter wheels are easier to push, but are more prone to 'skip'. The size of the wheel affects how transportable and compact the device is to carry.
Tire/Wheel type: Hard plastic wheels are cheaper, but more difficult to push. Rubber Balloon tires are most expensive, but result in smoother measurements.
Counter: The distance counter is typically located on the hub of the wheel, but more advanced models may have a handle mounted display. The unit of distance measured varies from hundreds (000.0) to tens of thousands (00000) of feet/meters. Usually wheels are fixed to measure either feet or meters at the factory.
Handle: The design of this feature range from simple 'broom handle' type poles, to ergonomically designed, foam filled grips. In general, the more elaborate the handle, the higher the unit costs.
Inexpensive: With most models costing less than $50, measuring wheels are cheaper than long distance tape measures or higher-technology solutions like laser distance finders.
Easy to use: No special training is required to use a measuring wheel. The only prerequisite skill required is walking in a straight line. Since the counter displays the distance traveled, more skill is required to use a traditional 'tape measure' than a measuring wheel.
Measurements "Good Enough": While wheels may not measure distances down to exact inches or fractions of a foot, they are precise enough for video surveillance work.
"Wheel Skip": A common shortcoming of measuring wheels is that wheel contact with the ground must be maintained at all times because of 'free-wheeling' or 'wheel skip' that can inaccurately change the distance traveled.
Off-Center paths: For true 'point A to point B' measurements, a straight line must be walked. Since the wheel records the distance actually traveled, if the path is off-center or wanders, distance readings can be inaccurate. This aspect is of special concern to video surveillance work when figuring trenching paths, wire runs, or field of view calculations.
Rough Terrain: Bumpy, uneven, muddy, and non-paved surfaces all make wheel measurement difficult. Not only do the aspects mentioned above come into play, the wheel itself can become dirty or damaged when measuring rough surfaces.
Reading the Display: Typically, the display for the wheel is placed at or near the bottom of the unit, ofen requiring the operator to bend over and/or stop to see the current measurement.
Slow: Since you need to stay straight, avoid wheel skip and look down to check the measurement, typically one walks slowly with the measuring wheel, making it a more time consuming process than using a laser distance finder.