We set it up for 1 metre from the bottom and pressed go. It also enables the profiles to be performed at a set time interval or just manually. The SeaRobotics control software allows you to setup profiles either to a set depth or distance off the bottom (from the multibeam nadir). There is no getting around it if you want to be accurate. So yes, you need to take sound velocity profiles in lakes and rivers too. 20 metres per second difference in just 12 metres of water. Well the initial test was done in the small lake behind SeaRobotic’s workshop and this is the profile.
It is impossible to conduct an accurate hydrographic survey without measuring the full sound velocity profile but how do you take a profile when you are not on the vessel? You might say that “I work on lakes and rivers, surely that isn’t necessary?”. The result – streaming video at about 2 Mb/s for 6.2 km away. The test was actually quite simple – turn on the ASV batteries and then connect to the onboard video camera. Harry was driven to the bridge in the distance and actually ended up 6.2 km away.
The image is of the base station antenna installation. Stuart, Florida has a handy set of bridges that cross over the Inner Coastal Highway which happen to be approximately 6 km apart. The theoretical range is 6 km which will then become the actual operating range of the ASV so this needs to be tested. Harry is fitted with an airMax 5.8 GHz 360 deg antenna and the base station has a 180 deg transceiver which can also be focused.
The SeaRobotics ASV is autonomous but it is always good to see what is going on and how do you communicate nowadays – by Wifi of course. ASV Harry has just completed his acceptance trials and there were a number of tests that we performed which are unique to ASVs, which I thought I would share.