Tuesday 28 July 2015

A day in the life of an EM Surveyor

Over the past few weeks we’ve covered what an EM Survey is, and the different benefits of completing one on your farm. But what I’d like to do today, is give you a bit of an insight into how we at Agri Optics do an EM Survey, ensuring that you receive top notch quality data to help with your ‘precision decisions’. So here we go…

Our surveyor arrives at the farm nice and early. When we get there the gear needs to be all unpacked out of the trailer and set up for the day ahead. Our Polaris needs to warm up and while this is happening the Trimble RTK GPS base station is  set up ready for logging the DualEM data. This base station is highly accurate and gives us horizontal accuracy of +/- 2cm.

Next, we need to plan the survey in conjunction with the farm manager (this often happens before we come on site to do the survey), starting with areas that need to be done first for management reasons, such as working around cows in paddocks etc. Additionally we need to know of any hazards and other features that might influence the survey, such as buried wire guidance, pipes, etc. Once we know all these factors we get on with the job.

To complete the survey we drive the Polaris towing the DualEM around the outside edge of the paddock, once near the fenceline and the second time a few metres in from this. Then we drive up and down at 12 metre intervals along the length of the paddock at approximately 15km per hour. The spacing and consistent speed is important in collecting and processing quality data across the entire survey. We use AB guidance lines on our Trimble FmX to ensure that we drive as straight as possible and reduce overlap which would cost us time and you money. We then complete the survey of the rest of the paddocks in the same way – around the outside and then up and down along the paddock.

(excuse the video, it's a bit shaky sorry!)

As we all know, electronic equipment can be slightly temperamental sometimes and we need to put a few checks in throughout the day to make sure that the DualEM sensor is running as it should. To do this we re-survey transects across previously surveyed areas a few times during the day, making sure that the readings don’t change and ensuring the DualEM is working to its maximum potential.

So, now we’ve completed surveying on all paddocks for the day and have ensured that the data is high quality data by performing these transects and doing a few checks. We then look at the raw (unprocessed) DualEM data out in the field and pick out a few areas that show different EM readings. We go to these points and take soil cores using a corer that is 2.5cm in diameter and 30cm long. We complete a visual observation of the soil, relating these to the EM map. The cores are taken as deep as we can possibly go and then placed carefully on a tube with depth markings on it. With the cores carefully lined up on this marker, we then take notes on parameters such as the depth of topsoil, amount & size of stones, textural properties at different depths and so on. All of these properties help add to the understanding of the final EM map.  

After this the day is almost done. Clean the gear and pack it away safely for next time before the surveyor goes home for the night to look at the EM data collected during that day on their laptop and get a good nights rest ready to do it all again tomorrow.

Blog post written by Jemma Mulvihill from Agri Optics NZ Ltd. To find out more about EM Surveying or any of the topics discussed in this blog call Jemma directly on 021796124 or visit the Agri Optics website.