Early tide display devices did not have enough memory to store any significant amount of future tide information and therefore they were programmed to calculate the occurrence of high and low tides based on a mathematical algorithm. One such device is taught in U.S. Pat. No. 4,412,749 issued to Showalter in November 1983. As it became less prohibitive to store large amounts of data, tide display devices were pre-loaded with future tide heights. While in many cases the devices were loaded with accurate data, many of the early devices, particularly watches, failed to display the information with enough specificity so as to be meaningful to the user. For example, the watch taught in U.S. Pat. No. 5,293,355 displays the times for the high and low tides but does not indicate the height of the highs and lows. Another example is the watch taught in U.S. Pat. No. 5,115,417 which represents tide height using a “tide height bar”. The tide height bar is basically a set of 8 horizontal lines printed on the watch face with the bottom line representing “low” tide and the top line representing “hi” tide. To indicate the height of the tide, an indicator is illuminated alongside one of the horizontal lines. Unfortunately, the tide height bar has no calibration to indicate the height of the tide and the tide height bar is so small that it is extremely imprecise. These drawbacks make the watch taught in the '417 patent impractical for any use that requires accurate knowledge of the tide height. Moreover, there is no way to know when the highs and lows for the day are going to occur.
Another device that displays tide graphically is taught in U.S. Pat. No. 6,295,248. The '248 device allows a user to select a geographic region and then displays the tide for the selected region. Here again, the tide is displayed in a very small display area and is therefore not precise enough to be of much use.
Perhaps to ameliorate the impreciseness of devices that displayed the tide graphically, U.S. Pat. No. 5,299,126 teaches an electronic tide watch that displays tide height as a numerical value. The watch described in the '126 patent gives a user more precise height information than can be gleaned from tide devices that display the tide height graphically. At the same time, however, the device of the '126 patent lacks other useful information such as whether the particular height is a high or low and whether the tide is rising or falling.
Traditional tide calculating devices were generally made for boat navigators and fisherman who needed to know whether the tide was high enough to pass over sand bars, shoals, and the like or whether the tide was low enough for a boat to pass under a bridge. Since early tide devices were used primarily by cargo ships, tide tables produced by the National Oceanic and Atmospheric Administration indicate tide heights at ports rather than at beaches where surfers are likely to be surfing. Thus, such tide tables were not of particular use for surfers who needed to know the tide at a particular local beach, not at a major port. Moreover, the devices that displayed the tide were of little use to surfers because they lacked a frame of reference. That is, devices that displayed the tide height numerically had no frame of reference as to whether the height was a high or a low, rising or falling, and devices that displayed the tide height graphically were imprecise as to the actual tide height.
Thus, there is a need for a tide display device that can display accurate tide information that is useful for surfers.