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BaseCamp Incorrrectly Calculating Direct Route Elevations

jamaubrit
I am using BaseCamp 4.0.2 hooked to a GPSMap62s with a Garmin GB Discoverer 50k All i.e the Ordnance Survey detail mapping of the UK at 1/50000 scale.

I have planned a number of circular walking routes in the English Lake District as Direct routes.

When the route is calculated the Graph profiler for each route shows the correct ascent and descent profile (and correct elevations) but the
Route Properties Elevation shows an Ascent value of (for example) 4666097613645408200000000000000000m and a Descent value of 0m.



It is the same for any Direct route, Ascent is always a very large 34 digit number and Descent is 0 meters.

In both the Properties and Route Directions tabs the Ascent columns in the grid also contain varying and very large numbers whilst the Descent column always shows 0 for each row in the grid.

For routes calculated using any of the other routing options, such as cycling (or bicycling as the Americans seem to like to call it) the Ascent and Descent values are calculated correctly.

Given that the Graph profiler shows the correct profile (and therefore knows from the OS mapping the correct elevations for a given route) what is causing the problem with the Ascent/Descent calculation?
  • Former Member
    0 Former Member
    I apologize for the inconvenience.

    The ascent/descent on the profile is calculated differently than the ascent/descent displayed on the properties page.

    However, ascent/descent for direct routes works fine with the Topo maps that I have installed (Topo France, Germany, US 24K). Which makes me think that your map while it has elevation data, does not have it in DEM format which is what we need to calculate ascent/descent for direct routes.

    Is this an older map? I don't have it here, so I cannot test it.
  • 0
    Thanks.

    The map-on-a-chip is the Garmin OS Discoverer 50k All purchased new with a GPSMap62s in January 2011 so I would not classify that as "old". This is the equivalent of a Topo map anywhere else in the world, it is the most detailed UK mapping that is available at that scale and would be used by any walker/hill walker in the UK.

    The map details listed in Basecamp are:

    © Acsi Publishing B.V. 2008
    © Crown copyright 2005. Licence number 100038946. 2010
    © Garmin Ltd. and Its Subsidiaries 2010
    © Navteq All rights reserved. 2009


    The Garmin website quotes for the Garmin GB Discoverer™ series:

    "Navigate with Ordnance Survey mapping on your Garmin GPS. Available in 1:25K and 1:50K scale maps with detailed topographic data including terrain contours, topo elevations, summits, paths, routable roads and geographical points."

    If the routing process calculates ascent/descent correctly between waypoints for standard routing profiles e.g. Bicycling, Automotive etc why should it fail when calculating ascent/descent between waypoints for the Direct profile? The correct elevation of each waypoint is listed in the grid display but how do you determine (as a user) if the map contains elevation data in DEM format? From the details listed on the Garmin website it is reasonable to assume that "topo elevations" means that route elevation data is included and would be calculated correctly regardless of the profile used.

    The 3D button in BC also works and renders the map in 3D which implies that DEM is present.

    If you don't have access to a Garmin OS Discoverer map download the free open source "OS 1:50K Look and Feel Mapset For Use With PC ONLY (MapSource or BaseCamp)" from the http://talkytoaster.info/ukmaps.htm website and use this with BaseCamp. It works in exactly the same way and exhibits the same characteristics when calculating Direct routes.

    I'm off to the mountains on Friday with my GPS so hopefully it won't lead me over a precipice!
  • Former Member
    0 Former Member
    I downloaded the map you pointed out and that map has no DEM (Digitial Elevation Model), or at least it doesn't say it does so BaseCamp doesn't query for it.

    3D is enabled for all maps now, and the maps certainly have elevation data. However it's not in the proper format. DEM allows you to pretty much grab elevation from any point of the map, if you only have contour lines we have to do some gymnastics to get the data out. This is pretty expensive (in terms of performance) so this is why we only do this for the profile, not for route ascent/descent. I'll have to do some more investigation what's going on with these maps.

    I apologize for the trouble.