A display hierarchy decides what an operator sees; the navigation scheme decides how they get there. It is the whole set of mechanics - navigation bars, menus, breadcrumbs, favorites, and links straight from a device to its faceplate - that let an operator move between screens without stopping to think. Where the hierarchy is the map, the navigation scheme is the roads, and the two only work together. A beautifully organized set of displays is useless if reaching the one you need takes six clicks and a guess about which menu it lives under.
HMI Navigation Scheme in one line: An HMI navigation scheme is the collection of controls and links an operator uses to move between displays - navigation bars, hierarchical menus, breadcrumb trails, favorites, and direct object-to-faceplate jumps. A good scheme is shallow and predictable, so any display is reachable in a couple of clicks and the operator always knows where they are and how to get back.
Several navigation devices usually work side by side on a modern HMI. A persistent navigation bar, docked at the edge of every screen, gives one-click access to the top-level overview and to each major area or unit. Hierarchical menus, often drop-downs off that bar, let an operator walk down from an area to a unit to a specific piece of equipment. Together they cover the planned, structured way of moving through the display set, and they mirror the display hierarchy itself so that the path an operator clicks matches the mental model they already hold.
Two devices handle orientation and the fast paths. A breadcrumb trail, shown as something like Plant then Compression then K-101, tells the operator exactly how deep they are and gives a single click back up to any parent level, which prevents the lost feeling that comes from drilling down through several unfamiliar screens. Favorites, or user-defined shortcuts, let an operator pin the handful of displays they touch constantly so they skip the menu walk entirely. The most powerful path of all is the direct object link: clicking a pump symbol on a mimic opens that pump's faceplate, and clicking a unit on an overview jumps straight to that unit's detail. These object-to-faceplate jumps mean the graphic itself is the navigation, and the operator never has to translate what they see into a menu name.
A well-built scheme also handles return paths deliberately. A back button that retraces steps, a home button that always lands on the same overview, and consistent close behavior on popup faceplates all reduce the small decisions an operator has to make. When every screen exposes the same set of navigation controls in the same place, movement becomes muscle memory rather than a task.
Navigation is easy to ignore when the plant is calm and painful when it is not. During an upset the operator is under time pressure, alarms are annunciating, and cognitive load is already high. Every extra click, every moment spent hunting for the right menu item, is attention pulled away from diagnosing the problem. This is why high-performance HMI guidance pushes for a shallow hierarchy - a small number of levels between the overview and any detail screen - and for consistent, predictable paths that do not change from one area to the next.
Predictability is as important as depth. If the pump faceplate opens from the mimic on one unit but requires a menu on another, the operator carries two rules instead of one, and under stress the wrong rule surfaces. Uniform placement of the navigation bar, the same click behavior on every device symbol, and breadcrumbs that always read the same way remove that ambiguity. The goal is that an operator who knows how to reach one display knows how to reach all of them, because the rules never change.
Speed to a display is often expressed as a target such as reaching any operating screen within two or three interactions from the overview. The number matters less than the discipline behind it: navigation should be designed and tested, not left to accumulate as screens are added over the years. Sprawling, inconsistent navigation is one of the quiet ways an HMI degrades, and it shows up exactly when the plant can least afford it.
The navigation problem changes shape when the operator is watching hundreds of remote sites rather than one plant. In a cloud SCADA platform such as Merobix, the top level is not a single overview mimic but a map or list of wellsites, pads, or facilities spread across a region. Navigation starts by letting an operator narrow that population - by area, by alarm state, by status - and then drill into one site's detail without losing the sense of the whole fleet. The same shallow-and-predictable principle applies: from the fleet view, a specific tank or compressor should be a click or two away.
Cross-site navigation also has to bridge the gap between overview and equipment cleanly. A pin on the map that is flashing an alarm should link directly to that site's screen and, ideally, straight to the point in alarm, the same way a device symbol on a plant mimic opens its faceplate. Breadcrumbs earn their keep here because a distributed operation naturally has more levels - region, area, site, unit, device - and an operator drilling five deep into an unfamiliar remote location needs an obvious way back up to the fleet.
Because remote monitoring is often done from browsers, tablets, and phones as well as a console, a cloud navigation scheme has to stay usable when the screen shrinks. Favorites and search become more valuable when there is no room for a wide navigation bar, and consistent behavior across devices keeps an operator effective whether they are at the desk or responding to a callout on a phone in a truck.
The display hierarchy is the organized structure of screens - overview, area, unit, detail - and what belongs on each level. The navigation scheme is the set of mechanics that move an operator between those screens, such as navigation bars, menus, breadcrumbs, and object links. The hierarchy defines the destinations; the navigation scheme defines the routes to reach them.
High-performance HMI practice favors a shallow scheme where any operating display is reachable in roughly two or three interactions from the overview. The exact number is less important than keeping paths short and consistent, because every extra click costs attention during an upset. Direct object links from mimics and pinned favorites help keep frequently used screens one action away.
Breadcrumbs are a small trail, such as Plant then Compression then K-101, that shows how deep the operator has navigated and lets them jump back to any level with a single click. They prevent the disorientation that comes from drilling down through several detail screens. In distributed cloud SCADA with many levels between the fleet view and a single device, breadcrumbs are especially valuable.
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