Comparison Lowrance HDS-7 Gen3 vs Lowrance HDS-9 Gen3

Sonar support for CHIRP technology.

The meaning of this technology is to use the echo sounder at the same time several frequencies. In other words, each pulse consists of several signals, each at its own frequency. According to the creators, this allows you to improve image quality, increase detail (including at great depth and high speed) and at the same time reduce the level of noise and other interference on the screen compared to single-frequency sonars. However, models with CHIRP are noticeably more expensive.

Availability of the side scan function in the echo sounder.

Devices with this feature are able to "see" the bottom and underwater objects not only directly under the vessel, but also on the sides of it. Note that different models can differ markedly in the angle of coverage of the side space. However, the side scan anyway expands the capabilities of the echo sounder and provides additional features compared to the usual bottom one.

Echosounder support for special bottom scanning technologies.

"Viewing" the space under the bottom of the boat is a classic sonar mode and is supported by all models by definition. However, in normal mode, the sound beam propagates in the form of a cone, and the area of the bottom that falls under the beam has the shape of a circle. This degrades the accuracy and does not allow you to achieve a detailed image. Thus, many echo sounder manufacturers have developed special technologies to improve the performance of the instrument; Lowrance has DSI, Hummingbird has DI, Garmin has DownVü. The nuances of these technologies may differ, but the basic principle of operation is the same: the echo sounder beam narrows and goes not in a cone, but in a strip. Due to this, the resolution of the device is significantly increased; at shallow depths, such an echo sounder can “draw” even individual stalks of algae, making it possible to distinguish underwater thickets from schools of fish. Some models combine a narrow beam with a classic cone to further expand detection capabilities. However, such devices are expensive.

— Screen size. Diagonal screen size in inches. The larger the screen, the more information can be displayed on it and the more detailed this information can be. On the other hand, this parameter noticeably affects the dimensions of the device, and large screens are expensive, especially since you need the appropriate resolution for normal image quality (see below).

— Touch. The presence of a sensor in the design of the display. This feature allows you to control the device by touching the icons on the screen — similar to how it is done in smartphones and tablets. Touch control provides more options than the classic one, using buttons and switches, besides it is more visual — however, such devices are more expensive.

— Display resolution. Display size in dots (pixels) horizontally and vertically. The higher the resolution, the more detailed image the screen is able to produce, the smaller objects can be clearly displayed on it and the more comfortable viewing. At the same time, the specificity of echo sounders is such that too high resolution is not required even for high-end models: for example, modest by the standards of smartphones or tablets 640x480 with a 5" screen are considered quite sufficient even for an advanced device.

— Colour. The ability of a screen to display colours. In this case, the simplest division is used:

Monochrome.... Displays that display information only in shades of one colour. Theoretically, the main colour can be any, but in this case, the vast majority of monochrome screens are black and white. Their advantages are low cost and energy consumption, as well as good visibility in the sun; at the same time, such an image allows you to work with quite a variety of types of data, which is enough even for very advanced echo sounders (see "Type"). However, this variety is not as wide as for colour displays, as a result, for chartplotters (see ibid.), such an image is not suitable — if it is impossible to display different colours, some of the important information on the maps is lost.

Coloured. Screens capable of working with multiple colours. The variety of colours can be quite small, but the image still turns out to be more informative than black and white: different colours can indicate different depths on the map, water temperature changes, etc. Due to this, this type of display is found in all types of navigation devices (see above). Its main disadvantage can be called a higher cost than that of monochrome screens.

— Backlight. The screen has its own backlight system. This feature makes the display independent of ambient light and allows you to see the information on it even in complete darkness. At the same time, the backlight increases power consumption, which is important during long-term operation from an autonomous source (for example, a boat battery). Therefore, it can be turned off.