MSP40 MOBILE SENSOR
PLATFORM

The MSP40 Mobile Sensor Platform comprises a wheeled resistance array, upon which a fluxgate gradiometer can also be mounted, providing fast, simultaneous, detailed resistance and magnetic surveys.

The platform comprises four spiked wheels set 0.75m apart on a rugged aluminium and stainless steel frame. A Geoscan Research RM15 Resistance Meter (supplied separately), DL256 data logger unit and MPX40 multiplexer unit are mounted centrally. A Geoscan Research FM256, FM36 or FM18 (supplied separately) can be attached using a mounting bracket (supplied). Each pair of wheels has independent suspension to allow the wheels to maintain contact with undulating ground and a pair of quick-release/latch handles allows steering along traverse lines and rapid traverse shift at grid edges when zigzag surveying. The logger unit can either act as a sample trigger system (in the same way as an FM256), or can be triggered by an optical encoder system integral to one of the wheels. The logger unit captures resistance measurements from the analogue output of the RM15, controls the multiplexer unit (which allows multiple resistance data sets to be collected) and triggers the gradiometer. Start/Stop control buttons are mounted on each handle to control the measurement system.

The system permits a new range of arrays for fast, detailed surveys - as fast as 7.5 minutes per 20m grid and up to 8 samples/m. Square array measurements avoid the trailing cable of a Twin array. Multiplexed square array measurements allow collection of alpha and beta data which provides important directional information. Twin arrays are also possible. Wings and struts can be used to extend the wheelbase from 0.75m to 1.25m. Since the gradiometer is mounted on the platform, away from the operator, the requirement for non-magnetic personnel is relaxed and allows use by less skilled operators eg new students. The platform can also reduce periodic errors in gradiometer data.

Roman Fort, Drumlanrig 2004 (Data reproduced courtesy GSB Prospection and Time Team)

Single square array data (0.75m alpha). Data sampling 4/m, 20m grids, Area = 140m x 120m. Plotting range 4 to 12 ohms. Black is high resistance. Internal roadways are clearly visible, along with buildings and other fine detail.

COMPARISON OF SQUARE AND 0.5M TWIN PROBE ARRAYS
Comparative surveys were made over the site of a Roman villa, Dunkirt Barn, UK, with the MSP40 and a standard 0.5m Twin probe array. Square array data were collected using the MSP40 with multiplexer unit, giving alpha and beta data, each at 2 samples/m. Twin array data were collected using a 0.5m PA5 probe array at 1 sample/m. Traverse interval was 1m in both cases.

Alpha       A       B                        Beta       B       N
                 ----->                                          ----->
               M      N                                      A       M

Data were despiked to remove noise generated by the substantial number of surface flints, then interpolated to 0.25m, giving the data shown opposite, both plotted at the same Standard Deviation scales for comparison. Although there are subtle differences, the overall correspondence is excellent, indicating the square array can be a viable alternative to the Twin.

Roman Villa, Dunkirt Barn 2005 (Data reproduced courtesy English Heritage)

0.75m Square array - alpha and beta combined. Data sampling 2/m for both alpha and beta. Plotting range -1.5 to +2SD,  5 to 10 ohms. Black is high resistance.

0.5m Twin probe array. Data sampling 1/m. Area = 60m x 80m. Plotting range -1.5 to +2SD. Black is high resistance.

HIGH RESOLUTION MULTIPLEXED RESISTANCE SURVEYS

Sampling of up to 8 samples/m allows fast, detailed resistance surveys to be undertaken. For example, the survey of the Roman Fort at Drumlanrig, shown opposite, where only the alpha array was used, was achieved at a rate of about 7.5 minutes per grid.

If the multiplexer is also used, this opens up the possibility of detailed directional studies. Comparative Square and 0.75m Twin array high resolution surveys were made with the MSP40 over a filled-in Victorian ornamental pond, Littlemoor Castle, W.Yorkshire. Alpha and beta data were collected, both at 4 samples/m, followed by Twin-broadside and Twin-longitudinal, also at 4 samples/m. Speed was 1.75s/m for the Square and 2s/m for the Twin.

The major responses  are very similar for all arrays. However, field drains running N-S are most clearly visible in the alpha mode as high resistance features (see adjacent and plots below), whereas they appear in the beta and Twin-longitudinal as very faint low resistance features, probably as a result of multiple responses over near surface features that are small in comparison with the array size. The beta mode highlights a diagonal drain better, and so combining the alpha and beta results in Geoplot gives optimal directional information. A further example of high resolution surveying at Jarlshof, Shetland,  may be seen on our website.

Victorian Pond, Littlemoor Castle

Square array - alpha. Sampling 4/m

Square array - beta. Sampling 4/m

SAMPLING SIMULTANEOUS RESISTANCE AND MAGNETIC MEASUREMENTS
Adding a gradiometer to the MPS40 provides complimentary information to the resistance data with no time penalty but double the productivity. A larger survey was undertaken at Littlemoor Castle, this time with alpha and beta data both at 2 samples/m, and an FM256 at 4 samples/m. Each 20m grid was surveyed in about 10 minutes.

The results shown below highlight the complementary information obtained. The positive magnetic responses greater than 15nT, shown as contours in the right hand plot, clearly respect the western and southern internal boundary of the pond, revealed by the resistance data shown in the left hand plot. The magnetic response reveals an EW pipeline not visible in the resistance survey. There is a good correlation between the resistance and magnetic responses for the group of features just to the north of the pipeline.

Square array data - alpha and beta combined. Data sampling 2/m for both alpha and beta. Interpolated to 0.25m x 0.25m. Area = 40m x 80m. Plotting range 5 to 15 ohms. Black is high resistance.

High Pass Filtered (10x10) alpha and beta data combined.

FM256 gradiometer data measured at 4 samples/m.
Plotting range +/- 5nT. Black is positive.

Contours of gradiometer data (+15nT) overlaying square array data (Geoplot processing).

20m

SPECIFICATIONS                                                                                                                      Back to top of page