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Ladders, Stairs, and Ropes, Oh My!

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  • #31
    Contour lines are "hard-coded" into the map at the time the map is produced. You can't convert them afterwards into feet or change their interval distance.

    You can set the measurement system to Imperial system but that'll only show *calculated* distances and elevation gain in miles/feet. It won't show contours in feet because they're hard-coded in the map.

    What can you do with contour lines (in vector maps)? You can display/hide them. By modifying the map's Theme, you can alter the weight of the contour lines (thicker/thinner) depending on the zoom-level, or their color. Beyond that, nope.


    There's a feature in Locus Map called Dynamic Altitude and it can serve as a workaround. It shows the altitude at the cursor's position. If you set the altitude units to feet, wherever you place the cursor on the map you'll see that location's altitude in feet.

    http://help.locusmap.eu/topic/vector..._lines_in_feet
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    • #32
      Originally posted by Trail Boss
      Contour lines are "hard-coded" into the map at the time the map is produced. You can't convert them afterwards into feet or change their interval distance.

      You can set the measurement system to Imperial system but that'll only show *calculated* distances and elevation gain in miles/feet. It won't show contours in feet because they're hard-coded in the map.

      What can you do with contour lines (in vector maps)? You can display/hide them. By modifying the map's Theme, you can alter the weight of the contour lines (thicker/thinner) depending on the zoom-level, or their color. Beyond that, nope.


      There's a feature in Locus Map called Dynamic Altitude and it can serve as a workaround. It shows the altitude at the cursor's position. If you set the altitude units to feet, wherever you place the cursor on the map you'll see that location's altitude in feet.

      http://help.locusmap.eu/topic/vector..._lines_in_feet
      Understood, especially with old picture based maps. With vector maps, one would think the rendering software could reinterpret the data and redraw the lines, or at a minimum, change the lables to feet. The latter being very easy I would think. I did see that in Caltopo, we can now load Google terrain maps, which are in feet. These look great, but aren't real good for navigation purposes.

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      • #33
        RE: Changing the labels from meters to feet. Contour lines labeled 1000, 1050, 1100 meters would become 3281, 3445, 3609 feet. I don't think many people would find that to be satisfactory.

        RE: Redrawing the contour lines. "Would that it were so simple!"

        https://youtube.com/watch?v=kGpsXuMvApo


        In a vector map, roads, rivers, power lines, contour lines, trails, etc are just lines. These lines identify their purpose (road vs river) so the map's theme can render them correctly (i.e. proper line-weight and color). The lines are represented as a list of points ("connect the dots") where each point is a geolocation (latitude and longitude).

        What you're proposing ("reinterpret the data and redraw the contour lines") is a capability most mapping apps do not have ... and for good reason. Normally there's no need to reposition anything on a map. A road is drawn where it ought to be and end-users have no need to nudge it over a bit. Arguably, relocating contour lines is the one special case where relocation (to convert from metric to imperial units) might be useful.

        Currently, the coordinates for drawing contour lines are calculated, using a 3D model of the terrain (using Digital Elevation Models from one or more sources; see Viewfinder Panoramas), at the time the map is designed. The mapping app's job is to simply render this information and not recalculate it from scratch.

        Adding this ability would be a "big ask". It would be easier to have the imperial contour lines calculated in advance and included in the vector map. Using a theme, you could choose which set of contour lines to display, metric or imperial (i.e. no new abilities required; leverages the app's existing abilities).

        Having said that, the market for maps with "metric/imperial contour lines" is constrained to the USA; the rest of the world works in metric. A greater hurdle is that many popular mapping apps don't even have the ability to handle vector maps, only raster maps (i.e. what you called "picture based" maps).

        I'll submit this as a new Idea on Locus Map's forum and we'll see if anyone votes for it. Then it'll be up the development team to decide if it's worth their while to implement it.

        http://help.locusmap.eu/topic/lomaps...-lines-in-feet
        Last edited by Trail Boss; 01-04-2018, 12:40 PM. Reason: Typo.
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        • #34
          That makes sense. i was thinking that the contours were just a layer that could be added or not., and if they were, they could be fairly easily be reinterpreted to get around the odd feet issue you mention. understand that may not have been the easy way back in the day. Maybe the evolution to 3D viewers will make it happen.

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          • #35
            Originally posted by mga56grg View Post
            That makes sense. i was thinking that the contours were just a layer that could be added or not., and if they were, they could be fairly easily be reinterpreted to get around the odd feet issue you mention.
            I'm not following you here. I don't see how contours on a layer would "fairly easily be reinterpreted".

            The data originally used to create the contour lines is not included in the map (neither vector or raster). If all you have is the map (vector or raster), there's nothing in it that helps you recalculate the new position of the contour lines. You need a Digital Elevation Model (DEM) to provide the missing elevation data (latitude, longitude, elevation) to recalculate the contour lines.

            Maybe the evolution to 3D viewers will make it happen.
            Not sure what you mean but three-dimensional terrain data (DEM) is already employed by mapping apps. It's used to calculate elevation profiles for routes, to display hill-shading, and for other purposes like the Dynamic Altitude feature I mentioned earlier.

            Locus Map allows you to optionally download "Elevation Data" along with a desired vector map (LoMap):
            http://docs.locusmap.eu/doku.php?id=...dd_map_shading

            "Elevation Data" is data that resides outside of the map; it can be used with vector and raster maps. For example, AlpineQuest works with raster maps exclusively but it lets you download elevation data so that it can do hill-shading and calculate elevation profiles for routes.
            http://www.alpinequest.net/en/help/v2/elevations

            However, extracting and manipulating information from the DEM, for generating hill-shading or an elevation profile, is a compute-intensive operation. Having it dynamically recalculate contour lines would produce a very sluggish map on one's phone. That's why I suggested the imperial contour lines should be calculated at the time the map is produced. This spares the app from doing heavy-lifting. All it has to do is what it already knows how to do, namely display pre-calculated contour lines.


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