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Why Bikeroutetoaster is........

BlacktemplarBlacktemplar Posts: 713
edited March 2012 in The bottom bracket
.......Sh1te.

For fun I compared BRT's mileage on a short local run with Google Maps, Via Michelin and MapMyRide;

BRT = 24.6 miles
Google = 20.4 miles
Michelin = 20.3 miles
MMRide = 20.1 miles
Catye actual = 19.8 miles

So, despite using the same map engine as Google Maps, BRT overestimates mileage by some 20% or so. Must use it for all my SCR mileages then.... :twisted:

Anyone else come across gross inaccuracies on routing software? What's the best/easiest/most accurate package?
"Get a bicycle. You won't regret it if you live"
Mark Twain

Posts

  • alihisgreatalihisgreat Posts: 3,872
    I use Bikehike.co.uk just because i get on with the interface and find it very quick and easy to use.

    Although i don't export routes to use with GPS, I just use it to plan new routes and plan distances.
  • rolf_frolf_f Posts: 16,015
    You'd expect them all to be using much the same coding so the discrepancy is odd.

    However, a sample set of one isn't enough - you need to see if this is a consistent issue. And then ideally check the route with a GPS log (since a magnet sensor will probably over or under read slightly unless you were very fastidious in calibrating it).

    I'd find a route or two that someone has uploaded to the likes of Strava and plot that on the different sites.
    Faster than a tent.......
  • BobbinogsBobbinogs Posts: 4,841
    Does it really matter if any of the tools are the odd km out for distance or metres for elevation? The bike computer is not gauranteed either and many folks don't even calibrate (and let's face it, even if you calibrate but are 2 mm out, over 100 km that can add up).

    FWIW, I like RidewithGPS but only because I find it very user friendly. As you note, they all appear to use the same engine but have variances so I now just stick to one tool and have got used to it.
  • Rolf F wrote:
    You'd expect them all to be using much the same coding so the discrepancy is odd.

    However, a sample set of one isn't enough - you need to see if this is a consistent issue. And then ideally check the route with a GPS log (since a magnet sensor will probably over or under read slightly unless you were very fastidious in calibrating it).

    I'd find a route or two that someone has uploaded to the likes of Strava and plot that on the different sites.
    I've suspected it was over-egging mileage for some time. Last year we did LEJOG and for each 100+ mile day the BRT distance was usually 10-15% more than two separately-calibrated bike comps (which were usually within a couple of miles of each other)

    At the end of the day it doesn't matter that much, I was just curious if it was a widespread issue with all mapping applications, or if it particularly narked people. Probably only relevant if you're doing big mileages or - like me - are particularly OCD :wink:
    "Get a bicycle. You won't regret it if you live"
    Mark Twain
  • RideOnTimeRideOnTime Posts: 4,712
    yes, I've found this but consistently wrong.. so consistent
  • kieranbkieranb Posts: 1,674
    the elevations can also be really out, I use ridewithgps and sometimes a fault shows up indicating a impossibly steep drop and climb where there is none, e.g. over a few meters on a flat section the elevation might drop 70m and back again, and this gets added to the total ride elevation.
  • MattC59MattC59 Posts: 5,408
    I just use the course plotter on Garmin Connect. Never had an issue with it.
    When I actually ride the routes, the distance (from speed sensor) is always within a gnat's c*ck of that which was indicated on Garmin Connect.
    Science adjusts it’s beliefs based on what’s observed.
    Faith is the denial of observation so that Belief can be preserved
  • Mike67Mike67 Posts: 585
    MattC59 wrote:
    I just use the course plotter on Garmin Connect. Never had an issue with it.
    When I actually ride the routes, the distance (from speed sensor) is always within a gnat's c*ck of that which was indicated on Garmin Connect.

    :D

    Tried that last week (Garmin connect)...ended up going along at least three rough tracks and turning back at one point as it ended up going into a field. All were marked as passable roads (albeit minor ones) when plotted on Garmin Connect.

    Wouldn't have minded but I was on my best wheels and tyres :(
    Mike B

    Cannondale CAAD9
    Kinesis Pro 5 cross bike
    Lots of bits
  • nwallacenwallace Posts: 1,465
    Thing to remember is:
    Mapping by manual plotting only follows the middle of the road according to the map.
    GPS accuracy can vary wildly during a ride
    "2mm" accuracy from a wheel sensor is considerably better than the 2 above.
    Terrain data depends entirley on what data set is in use, USGS used to have 90m "DEM" data available on a public FTP site, that means there is only a reading every 90m and some of them are missing, not sure exactly what asites are currently using though. A good GPS system with an excellent GPS signal may be more accurate than the terrain data.

    5km over read is shocking though, but if it uses google mapping then it should be using googles distance algorithm so should be the same... Unless BRT have decided to override it... But there's no point doing that as the algorithm used by google is the same one used by everyone using GPS co-ordinates.
    Do Nellyphants count?

    Commuter: FCN 9
    Cheapo Roadie: FCN 5
    Off Road: FCN 11

    +1 when I don't get round to shaving for x days
  • NWLondonerNWLondoner Posts: 2,047
    Mike67 wrote:
    MattC59 wrote:
    I just use the course plotter on Garmin Connect. Never had an issue with it.
    When I actually ride the routes, the distance (from speed sensor) is always within a gnat's c*ck of that which was indicated on Garmin Connect.

    :D

    Tried that last week (Garmin connect)...ended up going along at least three rough tracks and turning back at one point as it ended up going into a field. All were marked as passable roads (albeit minor ones) when plotted on Garmin Connect.

    Wouldn't have minded but I was on my best wheels and tyres :(

    That's what google streetview is for ;) or failing that use satellite view.

    That has saved my bacon/blushes when plotting a route before
  • Mike67Mike67 Posts: 585
    NWLondoner wrote:
    "Mike67 wrote:

    :D

    Tried that last week (Garmin connect)...ended up going along at least three rough tracks and turning back at one point as it ended up going into a field. All were marked as passable roads (albeit minor ones) when plotted on Garmin Connect.

    Wouldn't have minded but I was on my best wheels and tyres :(

    That's what google streetview is for ;) or failing that use satellite view.

    That has saved my bacon/blushes when plotting a route before
    [/quote][/quote]

    I know, my own fault...I plotted it in a bit of a rush as it was one of my 'squeeze them in when I can' rides.
    Also an area I didn't know with a Garmin 500...took me a while to figure out where I was once I'd gone off route :oops:
    (who said carry a proper map? :D )
    Mike B

    Cannondale CAAD9
    Kinesis Pro 5 cross bike
    Lots of bits
  • MattC59MattC59 Posts: 5,408
    NWLondoner wrote:
    Mike67 wrote:
    MattC59 wrote:
    I just use the course plotter on Garmin Connect. Never had an issue with it.
    When I actually ride the routes, the distance (from speed sensor) is always within a gnat's c*ck of that which was indicated on Garmin Connect.

    :D

    Tried that last week (Garmin connect)...ended up going along at least three rough tracks and turning back at one point as it ended up going into a field. All were marked as passable roads (albeit minor ones) when plotted on Garmin Connect.

    Wouldn't have minded but I was on my best wheels and tyres :(

    That's what google streetview is for ;) or failing that use satellite view.

    That has saved my bacon/blushes when plotting a route before

    Exactly what I was going to say :lol:
    If I plot a route down a country lane, I always check it out on Streetview before i ride it.
    Science adjusts it’s beliefs based on what’s observed.
    Faith is the denial of observation so that Belief can be preserved
  • rolf_frolf_f Posts: 16,015
    nwallace wrote:
    Thing to remember is:
    Mapping by manual plotting only follows the middle of the road according to the map.
    GPS accuracy can vary wildly during a ride
    "2mm" accuracy from a wheel sensor is considerably better than the 2 above.
    Terrain data depends entirley on what data set is in use, USGS used to have 90m "DEM" data available on a public FTP site, that means there is only a reading every 90m and some of them are missing, not sure exactly what asites are currently using though. A good GPS system with an excellent GPS signal may be more accurate than the terrain data..

    The GPS accuracy shouldn't (and in my experience doesn't) vary wildly during a ride. Repeated rides tend to come out withing 0.1 or 0.2 miles of each other and I don't think the error is cumulative.

    The route plotting following the middle of the road is irrelevant - it really makes no difference. More significant (but still probably insignificant) is the effect of corner cutting both in the plotting and by the GPS.

    The wheel sensor won't be considerably better in the real world - probably the 0.1 of a mile or so I referred to above.

    As for terrain - I really don't know what is right there! As you say, accuracy depends on the detail of the digital terrain map but that should still be fairly accurate as long as the amplitude of the real world ups and downs is greater than that of the DTM tiling. In that case, you just lose accuracy in the peaks and troughs so on a 5km climb, the only potential innaccuracy is in the first and last tiles. If, on the other hand, the route is up and down all over the place, there is more potential for innaccuracy. Either way, the websites should always underestimate (but not by much).

    The barometers on my GPS units tend to give notably different readings on repeat routes and generally far greater overall climbs than the websites imply. The websites at least offer consistency which is probably more important here whichever is actually more accurate!
    Faster than a tent.......
  • aztecboyaztecboy Posts: 384
    actually great.

    I bought a 705 after getting lost a few times on LeJog in 2008.

    Since then, routes created with BRT have guided my 705 and my tours faultlessly through end-to-ends of Ireland and France.

    These routes were also converted into ITNs and loaded into a TomTom in the support truck which followed extremely intricate routes without a hiccup.

    I find BRT really simple to use.

    For sure the advent of streetview has greatly aided the planning, but the routes got us hotel door to hotel door and was never a problem. The French tour (Toulon -Calais) was 10 days of 80-90 miles of delightfully quiet smooth French tarmac, how I miss it!
    aztecboy
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