Consistency of the RCM411 Measurements

Round 1, ./map/#RCMD04_20140218_1845

Consistency is a good measure of the usefulness of a sensor. In the same situation one should be able to repeat the measurement with same results. The client may see this as self-evident, but sensors that use complex indirect measurements may be surprisingly sensitive to small features in the measured substance. Optical sensors are typically sensitive to rapid variations in the ambient light level.

Teconer’s intent is to thoroughly test the performance of its sensors. Results of these studies are published as openly as possible. This information enables the customer to better understand the possible abnormal behaviour of a sensor.
This text documents a test where a 12km (8 miles) loop was measured three times. All temperatures were near freezing (0 °C) and light snow begun just before the first drive. The easiest way to look at data may be using the map links where all details can be shown just by clicking point of interest along the route.

Kierros 1, ./map/#RCMD04_20140218_1845
Kierros 1, ./map/#RCMD04_20140218_1845

The state graph shows a typical near freezing situation. Part of the road is wet and another part is frozen. There was very little residual salt on the wet, slightly bigger, road.

The second and third round give very similar results, as expected, because the conditions were essentially stable. The North going, initially wet section, shows somewhat more ice, when it snows on the salted water.


The friction diagram shows that the friction is partly even significantly better than during the later rounds. The reduction in friction may very well result from the snow and very little residual salt. In general the friction profiles repeat very well.


Kitkan kuvaaja

The water amount measurement is also very consistent. Current knowledge does not give a firm basis to specify the absolute accuracy of the results. The results are roughly correct and very applicable for road maintenance purposes. Other components (e.g. ice) make the estimation of the amount even more difficult.

Although there was no dry surface in this test, we know that RCM411 detects dry pavement very well in all circumstances. That is very important to know, because the dry surface seldom freezes, or at least does not rapidly become slippery. Many of our customers and partners are thus investigating the possibility to automatically control the salt spreader base on the measured water amount and maybe weather forecast. In a Swedish article the conclusion is that that kind of method would lead to significant reduction in salt use. Also the statistical (repeated measurements) amount of water on a certain road section might give a signal of expected problems in winter maintenance. As far as we know, this kind of ”water mapping” has not taken place anywhere. The RCM411 would be an excellent sensor in gathering the data.

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