Tidal sites were established at various locations, Port Adventure, Yankee River, Small Craft Retreat and of course Port Craig, to achieve a workable co-tidal model. Each site had a tide pole and two automatic gauges as a back up for each other (There’s nothing more frustrating than several days sounding only to discover you have no usable tidal data.) The two gauges used at each site were the Yeokal (which the RNZN had been using for a number of years) and the Valeport 740, which was under field trial. Both gauges were set to record the reading every 10 minutes. The gauges were to be downloaded manually every 5 days into a laptop, and the data formatted onboard ship for reduction of the MBES data.

New Zealand’s Wild Coast
Port Craig is located in Te Wae Wae Bay, on the southern coast of the South Island at the western approaches to Foveaux Strait. An early pioneer settlement, it is now uninhabited. All that remains of the port is part of the wharf, a breakwater and the odd bit of machinery reclaimed by the dense bush. With the area now part of Fiordland National Park and no roads access available the only people who venture there these days are hunters and the odd navy surveyor.

Setting Up
At Port Craig, due to the gently sloping sea floor and a 2.5m tidal range two tide poles, an inner and outer pole, were erected on old wharf piers. The gauges were situated by the outer pole where the seafloor dropped off steeply to 7 metres depth. With the aid of a diver, the installation of the tranducer/sensor went quite smoothly.

Problems Arise
A number of problems arose with the chosen site which could have been overcome with a different site (hindsight would be a wonderful tool in surveying!!). The gauges could only be downloaded from a boat, in our case a jet RHIB, and the notorious southern ocean weather conditions made it difficult for the RHIB coxÕn to remain alongside the pole. The gauges also needed to be downloaded at hightide to allow us to reach them. This was made all the more difficult by the fact that the gauge had to be downloaded via a 1m comms cable connected to the laptop. In the case of the Yeokal, the downloading process could take up to10 minutes.

Tackling the Mission
On the day the photo was taken the Yeokal gauge had not been downloaded for several weeks due to bad weather and the ship working in other remote parts of the survey ground. I was to download the gauge while Chief Petty Officer Mike Blatch accompanied me with a camera to get some photos of the site for our survey school.
Due to the long period since the last download the process would take longer than the expected 10 minutes thus putting more pressure on the task. Initial attempts to keep the RHIB alongside the pier in the ½m swell proved rather difficult. A further problem arose with the Yeokal gauge still actively recording data. This meant that every 10 minutes it would cease downloading for a minute to take a reading, this minute stop would sometimes switch off the comms link to the laptop thus requiring the whole process to be started again. The bowman had already lost his ICOM radio over the side helping me save the laptop from going to the bottom during one swell and it was looking if we would have to abandon the attempt.
Rather than return empty handed, we looked at our options, and that’s when I noticed a small wooden wedge about a foot under water used to keep the tide pole firmly in place vertically. Tying the laptop to myself, I instructed the RHIB cox’n to drop me off on the wedge and then wait off. I told Mike he should get a photo of this, his response… "yeah! One before you fall in with the Navy’s laptop and one after". With enough room on the wedge for one foot I connected the laptop to the gauge and commenced the download. I stayed there for the next twenty minutes hugging the pier and the laptop with the odd swell passing through to keep me alert and refreshing in my lower regions.
Although a tad cold and suffering a mild case of cramp, the result was a successful download which led to a successful reduction of the sounding data and ultimately a successful (if not trying at times) survey. I have used the photo on several occasions now to show young survey ratings that there are always ways to achieve your aim. Sometimes you just have to put yourself in precarious positions to do it.