Slope angle is the one terrain number we look at before every winter ride. It is free in Aventerra, it works offline, and it is the quickest way to tell which ground deserves a second thought. This guide walks through how we use it, step by step, and where it stops being useful.
Know what the number means
Slope angle is the steepness of the ground, in degrees. Avalanche Canada's glossary puts it plainly: most avalanches occur on slopes with an incline of 30 to 45 degrees. That range is the whole reason the layer exists. It tells you which ground is steep enough to slide, so you can see it from the staging area instead of discovering it under your track.
We did not come up with that range and we do not forecast anything. The app shows the shape of the ground. What the snow on that ground will do today is the job of the regional bulletin, and we come back to that at the end.
Turn on the Slope Angle layer
Open the layers sheet and switch on Slope Angle. Steep ground gets a colour wash over whatever base you are looking at: the vector basemap, satellite imagery or 3D terrain. We find satellite the easiest to read in open terrain, because the shading lands on features you can recognise from the truck.
The layer draws between zoom levels 10 and 13. That is where the elevation model has real detail. Zoom in further and the shading stays on screen but adds nothing new, so do your reading at those zooms, then zoom in to lay out the route.
Slope angle is free on every plan, and so is snow depth. We treat both as safety layers and they stay that way.
Tap the ground for the number
A colour tells you steep or not steep. The number tells you how steep. Tap anywhere on the map and open Terrain here. The sheet computes the slope on your phone from the elevation model and shows it in degrees, with the direct sun window and sun hours for that spot beside it.
Two things to keep in mind. The slope is averaged over one cell of the elevation model, so a short rollover or a small cliff band can hide inside a gentler average. And it is a reading of the ground, not a clinometer on the snow surface. Treat it as a strong hint, then look at the slope with your own eyes.
When the slope you tapped is steep enough to slide, the sheet says so and asks you to check today's bulletin. We put that line there on purpose. It is the point where the app stops and the forecast starts.
Look for the steepest ground nearby
A line that stays on gentle ground can still run under something steep. That is why the sheet also shows the steepest ground nearby, and how much of the ground around your point is over the steep threshold. Tap it and the map jumps to where that ground is.
Use this before you commit to a creek bottom or a bench. If the steepest nearby ground sits well above you, ask what happens if it releases and whether your line is in its path. Avalanche Canada's glossary describes the trigger point and the path an avalanche runs, which is the picture we want in our heads when we read that number.
Take the layer with you
Slope angle is one of the layers you can download. Add it when you frame an offline area and the shading comes down with the basemap. The layer and Terrain here then keep working with no signal, because the elevation data is already on your phone.
Satellite imagery can come with the area too, at a lower detail ceiling than it shows online. Add it and the offline map draws slope over imagery; leave it out and the shading lands on the vector basemap and hillshade. Our habit is to read the terrain at home over full-detail satellite, then rely on the downloaded area in the field.
Read the bulletin before you go
The slope layer answers one question: is this ground steep enough to slide? It does not answer whether it will slide today. For that, read the regional forecast the morning you leave. In most of Canada that is Avalanche Canada's forecast, where you search your destination and read the danger ratings by elevation. In the Chic-Chocs it is the Avalanche Québec bulletin, published daily through the winter season.
Take a course too. Avalanche Québec lists its training sessions, and Avalanche Canada keeps resources for mountain sledders, including training providers. Avalanche Québec's advice for snowmobilers is to keep the rescue essentials in a pack on your body, not on the machine. The layer is a planning tool. Your training and the bulletin are what keep you off the wrong slope on the wrong day.
Slope angle is one part of the terrain tools in Aventerra, alongside 3D terrain, contours and the on-device terrain sheet. The Terrain and slope page covers where the elevation data comes from and what the layer does not do.